Media reckons science now proves ‘carbs’ are fine again

Reading newspapers can lead to confusion about the best diet choices

“Eat more ‘good’ carbohydrates and less protein for a longer life,” reports the Mirror.

It seems like only last week that the media was advising us to eat less carbohydrates. The reality is that neither today’s “pro-carbs” or recent “anti-carbs” news stories have changed government food advice.

Today’s news refers to a short study of different diets on a relatively small number of mice – not people. It’s always a fairly safe bet that studies in mice have few implications for the British human public – and today’s news is no exception.

And the study did not look at “good” or “bad” carbohydrates, nor the effect of the diet on lifespan. Instead, mice randomly got to eat one of three diets, with either unlimited access or in a calorie restricted fashion. All diets had 20% fat content, and then either a high, low or medium protein to carbohydrate ratio.

As expected, mice fed calorie restricted diets lost the most weight and had good metabolic status. Mice fed unlimited low protein, high carbohydrate diets ate the most amount of food and had the highest energy intake, but did not put on as much weight as the other two groups of mice fed unlimited food. The researchers say this was because they burned off more energy. These mice also had improved insulin and cholesterol levels similar to that observed for mice with calorie restricted diets.

Find out the truth about carbs.

Where did the story come from?

The study was carried out by researchers from the University of Sydney, Australia and the National Institutes of Health in Baltimore, US. It was funded by the National Health and Medical Research Council of Australia, the Ageing and Alzheimer’s Institute of Concord Hospital and the US National Institutes of Health.

The study was published on an open-access basis in the peer-reviewed journal Cell Reports, so it is free to read online.

Both the Mirror and the Daily Mail reported that “healthy” carbs such as fruit and veg may be the key to living longer. While this may be the case, neither the type of carbohydrates nor lifespan were studied in this piece of mouse-based research.

What kind of research was this?

This was an animal study using mice. The researchers wanted to directly compare the effects of different diets on indicators of health.

The authors point to previous research in which restricting calories by 30 to 50% increased “healthspan”, delayed the onset of ageing and age-associated diseases and improved metabolic health in most animal species that have been tested. They wanted to see if other diets could have the same effects without the calorie restriction, because most people find it difficult to limit the amount of calories they consume.

What did the research involve?

The researchers randomly assigned 90 mice to have either calorie restricted diets or diets with unlimited access to food for eight weeks. At the end of the eight weeks, the researchers compared the weight and metabolic status of mice between the groups.

All of the diets had 20% fat content and the same number of calories per gram. The diets were split into:

  • low protein, high carbohydrate
  • medium protein, medium carbohydrate
  • high protein, low carbohydrate

Mice fed the calorie restricted diets were given 40% of the average amount of food that the other group of mice ate.

What were the basic results?

After eight weeks:

  • Mice fed calorie restricted diets lost the most weight.
  • Mice fed unlimited low protein, high carbohydrate diets ate the most amount of food and had the highest energy intake, but did not put on as much weight as the other two groups of mice fed unlimited food. They had the highest level of energy expenditure out of all groups studied.
  • Mice fed unlimited low protein, high carbohydrate diets also had improved insulin and cholesterol levels similar to that observed for mice with calorie restricted diets, regardless of the type of diet.
  • Mice fed unlimited high protein and low carbohydrates had higher insulin levels and impaired glucose tolerance compared to mice in the other groups.

How did the researchers interpret the results?

The researchers concluded that after eight weeks, mice fed unlimited low protein, high carbohydrate diets had similar metabolic improvements as seen under calorie restriction. This was despite increased energy intake. Importantly, this was these mice also didn’t develop increased body fat and fatty liver that is observed in longer-term low protein, high carbohydrate feeding. They say that these results “suggest that it may be possible to titrate the balance of macronutrients to gain some of the metabolic benefits of [calorie restriction], without the challenge of a 40% reduction in caloric intake”.

Conclusion

This study has found that over a short time period, mice fed a diet that’s low in protein and high in carbohydrates gained less weight than those fed diets with higher levels of protein. It also found that mice lost weight regardless of the amount of protein and carbohydrate if the number of calories was restricted.

The researchers say that the mice fed unlimited low protein, high carbohydrate diets did not gain as much weight because they burned off more calories. In this study, their “metabolic status” improved compared to mice with unlimited higher protein diets. However, previous research has shown that low protein, high carbohydrate diets consumed over longer time periods have been associated with weight gain, increased body fat and fatty liver.

While this study has produced interesting findings, its use is severely limited because it had no control group to compare the diets against.

It is also not clear how the results of this study would be applicable to humans. Calorie restriction does cause weight loss in humans, but in the long term this can reduce the metabolic rate. Humans are also more complex and less likely to naturally burn off any excess calories consumed from a low protein, high calorie diet.

In conclusion, this study in mice does not change current human dietary advice to eat plenty of starchy carbohydrates, fresh fruit and vegetables, some milk and dairy foods, lean meat and fish (or other protein), and foods high in sugar, fat or salt to be eaten little or in small amounts.

The eatwell plate highlights the different types of food that make up our diet, and shows the proportions we should eat them in to have a well balanced and healthy diet.

 
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Half a handful of nuts a day ‘reduces early death risk’

Nuts may reduce inflammation while also helping to prevent cell damage

“A handful of nuts can save your life, says new study,” The Daily Telegraph reports after a Dutch study found a link between daily nut consumption and a reduced chance of dying from a number of chronic diseases, including cancer and heart disease.

The study assessed the dietary and lifestyle habits of middle-aged to elderly adults from the Netherlands and followed them up over the next 10 years.

Overall, researchers found people who ate nuts had a decreased risk of death from any cause as well as various specific causes, such as cardiovascular diseases and cancer, compared with those who didn’t eat any nuts. The most reduced risk was found with the consumption of 5-10g of nuts a day.

However, not all risk reductions were significant and some of the researchers’ analyses were based on very small numbers, which means some of the results may not be that reliable.

Also, it is possible nut consumption is just one factor that’s part of an overall healthier diet and lifestyle, and people who regularly eat nuts may be healthy in other ways.

Nuts are a good source of healthy unsaturated fats, protein, and a range of vitamins and minerals, so having them as a daily snack isn’t a bad idea (provided you’re not allergic). Unsalted nuts are the healthiest option.

Where did the story come from?

The study was carried out by researchers from Maastricht University Medical Centre in the Netherlands, and was funded by the study authors, who report no conflicts of interest.

It was published in the peer-reviewed journal, the International Journal of Epidemiology.

The UK media’s reporting of the study was accurate, though the inherent limitations of the study were not made clear to readers.

What kind of research was this?

This cohort study aimed to look at how the consumption of peanuts, tree nuts (such as Brazil nuts and almonds) and peanut butter was associated with mortality.

The researchers say nut intake has often been associated with lower mortality, but often studies have focused on cardiovascular outcomes and have not looked at death from other causes. Dose-response relationships are said to remain unclear.

This study looked into this using a large cohort of middle-aged to elderly people, who provided dietary and lifestyle information and were then followed up for 10 years.

The researchers looked at deaths and causes of death. They supplemented this by a search for the results of other similar published cohorts.

But the main limitation with this study is it cannot prove direct cause and effect, and any associations seen could be influenced by other factors.

What did the research involve?

Data was taken from the Netherlands Cohort Study, which recruited 120,852 middle-aged to elderly men and women (age 55 to 69 years) in 1986.

At enrolment, participants completed questionnaires on dietary intake, medical conditions, smoking and other lifestyle factors. The food frequency questionnaire covered food and drink consumed over the past year.

Nut and peanut butter consumption was assessed by questioning the frequency and portion size of peanuts, other nuts, mixed nuts and peanut butter, and summed to give total nut intake.

The cohort was followed for 10 years until 1996. Information on deaths and causes of death was obtained from Statistics Netherlands and the Central Bureau for Genealogy, which use valid medical codes (the International Classification of Diseases, ICD).

There were 18,091 deaths during the 10-year period. The researchers decided to compare the questionnaires of the people who died (cases) with a random sample of 5,000 people from the cohort who had not died (controls).

They excluded cases and controls who reported cancer or cardiovascular disease at study enrolment or those with incomplete questionnaire data, leaving a final sample of 10,382 people who died and a comparison group of 3,693 surviving members of the cohort.

They also conducted a supplementary literature search of one medical database to identify other published cohorts looking at links between nut consumption and cause of death.

What were the basic results?

Overall, the study found the average total nut intake in the cohort was 8.1g a day for men and 4.4g a day for women, with peanut butter 1.4g and 1.2g, respectively.

They found higher nut intake was associated with various other factors, including higher fruit, vegetable and alcohol intake, higher educational level, and, in women, not smoking and a lower body mass index (BMI).

In analyses adjusted for age and various other health and lifestyle factors, the researchers found there was a significant trend for people consuming more nuts to have reduced risk of death compared with those not eating nuts:

  • people eating 0.1-5g daily had a 12% reduced risk (hazard ratio [HR] 0.88, 95% confidence interval [CI] 0.78 to 0.99)
  • people eating 5-10g daily had a 26% decreased risk (HR 0.74, 95% CI 0.63 to 0.88)
  • people eating at least 10g a day had a 23% reduced risk (HR 0.77, 95% CI 0.66 to 0.89)

Looking at specific cause of death, they found trends for the risk of death from the following diseases to be reduced by nut consumption compared with no consumption:

  • cancer
  • cardiovascular diseases overall (and heart disease and stroke specifically)
  • respiratory disease
  • diabetes
  • neurodegenerative diseases (not specified, but includes Alzheimer’s disease, for example)
  • other causes of death

However, within the individual disease categories, as with overall deaths, there wasn’t a consistent linear pattern where increasing nut consumption was associated with lower risk.

For overall deaths and various diseases, the risk decrease seemed to be lowest for the middle consumption category (5-10g a day).

In some cases, the risk decrease for a particular consumption category just fell short of being statistically significant (one of the confidence intervals touching 1.0 or 1.1), meaning we can’t be sure this is a real decreased risk compared with non-consumption.

The researchers found peanut and tree nut consumption were linked with a decreased cause of death, but peanut butter alone was not. Possible reasons given for the differences between nuts and peanut butter were the addition of salt and trans fats in peanut butter.

Combining the results of other studies identified through their literature search found a 15% decreased mortality risk for the highest compared with lowest nut consumption (HR 0.85, 95% CI 0.77 to 0.93).

How did the researchers interpret the results?

The researchers concluded that, “Nut intake was related to lower overall and cause-specific mortality, with evidence for non-linear dose-response relationships. Peanut butter was not related to mortality.”

Conclusion

This Dutch cohort of middle-aged to elderly adults generally found people were less likely to die in the following 10 years if they ate a small number of nuts a day compared with none.

The study has strengths in its large sample size and that cause of death was followed up for the full cohort using valid medical codes.

However, there are various points to bear in mind before we jump to the conclusion that nuts are the magic ingredient that will slash our risk of death.

No clear trends

It is difficult to draw any clear interpretations about how nut consumption may be associated with risk of death overall or from specific causes.

There weren’t clear linear trends where increasing consumption was associated with increasingly decreased risk, and often the middle consumption category (5-10g per day) had the lowest risk.

This is roughly a small handful of nuts, depending on the type of nut. Not all of the risk decreases for different consumption categories or diseases were significant, meaning we can’t be sure there is any real decreased risk compared with non-consumption.

Small sub-group size

When looking at specific cause of death, some of the analysis was based on very small numbers of people.

The analysis for diabetes came from the comparison of 85 diabetes deaths in the non-consumption group, 46 in the 0.1-5g category, only eight deaths in the 5-10g category, and 19 in the more than 10g category.

Analyses based on such small numbers of people may be less reliable and are more likely to give significant findings by chance.

Use of food frequency questionnaires

Nut consumption was assessed through food frequency questionnaire. Though this is a valid method, it may introduce inaccuracies.

For example, many people may find it difficult to estimate roughly how many nuts, or grams of nuts, they eat a day on average over the course of a year. It is also not clear whether this takes nuts in cooked or baked items into account.

Potential confounders

Although the researchers have adjusted for various medical and lifestyle factors in their analyses, it is still possible that these effects, and other unmeasured factors, have not been fully accounted for.

That is, it is difficult to pin the direct cause of any decreased risk on nuts specifically. If nuts are associated, it is possible they are just one factor in an overall healthier diet and lifestyle.

Lack of information on cause of death

The study has looked at cause of death, but has not explored within these categories. For example, neurodegenerative disease or cardiovascular disease encompasses various diseases and health problems.

Specific population

Though this study involved a large cohort, these people are all a specific population of middle-aged to elderly adults from the Netherlands. The results may not be applicable to younger populations or those from other countries.

This study will add to the wide body of literature looking into the health benefits of different diet and lifestyle patterns.

But nuts aren’t for everyone: some people can have severe life-threatening allergic reactions to them. And it doesn’t provide proof that nuts alone are the magic health ingredient for a longer life.

Despite constant media reporting, there is no such thing as a single superfood that will prevent ill health and premature death. Eating a daily portion of nuts will do you little good if you smoke, don’t take any exercise, drink alcohol to excess, and are overweight or obese.

The best way to stay healthy is to take regular exercise and aim for a healthy and balanced diet that includes plenty of fruit, vegetables and fibre, limited saturated fat, salt and sugar, watch how much alcohol you drink, and avoid smoking.

Could eating spicy food help you live longer?

Spicy food lowers the risk of early death, a study claims

“Curry really could be the spice of life,” says The Daily Telegraph, reporting on a study looking at the link between regularly eating foods that contain capsaicin – found in chilli peppers – and the risk of dying early.

The study of nearly 500,000 people in China found those who ate spicy food once a week or more were about 10% less likely to die during the seven-year follow-up period than people who ate spicy food less than once a week.

However, the researchers say their work cannot prove that spicy food was behind the lower chance of death, and their work in China should not be taken to mean the same would be true elsewhere in the world.

Where did the story come from?

The study was done by researchers from China (Peking University, the Chinese Academy of Medical Sciences, and five regional Centers for Disease Control and Prevention), the US (Harvard School of Public Health and Harvard Medical School), and the UK (the University of Oxford). It is part of the China Kadoorie Biobank study, an ongoing study of half a million adults from areas around China.

It was funded by grants from organisations including the National Natural Science Foundation of China, the Chinese Ministry of Science and Technology, the Wellcome Trust in the UK and the Kadoorie Charitable Foundation in Hong Kong.

The study was published in the peer-reviewed BMJ, and the research can be read for free on the BMJ website.

The story has been widely reported in the media, with newspapers such as the Mirror claiming that the research shows “curry helps you live longer” – but the study was carried out in China, so people were unlikely to have been eating curry.

The Mirror claims that, “people who ate spicy meals like curry favourites tikka masala, jalfrezi and vindaloo once or twice a week were less likely to die than those who had them less”. The study did not look at consumption of Indian-style dishes such as vindaloo, but at how often Chinese people included chilli pepper or other spices in their diet.

What kind of research was this?

This prospective observational study aimed to find a link between regularly eating chilli or other spices and how long people lived.

Observational studies are good at finding possible links between factors such as diet and health. However, they cannot prove that one factor causes another.

What did the research involve?

Volunteers took a variety of tests and questionnaires relating to their health, family health, diet, exercise, income, tobacco and alcohol use, occupation and many other factors. They also answered a food frequency questionnaire, which asked how often they ate hot, spicy foods and what types of spices they used.

The researchers followed up the volunteers for an average of 7.2 years. They looked at whether people who eat chilli or other spices were more or less likely to have died during that time.

They adjusted their figures to take account of many factors we know affect length of life, such as smoking. They then calculated how likely people who ate spicy food regularly were to die, compared with people who ate spicy food less than once a week.

What were the basic results?

The researchers looked at data from 199,293 men and 288,082 women. During the study period, 11,820 men and 8,404 women died. Compared with people who ate spicy food less than once a week, people who ate spicy food on one or two days were 10% less likely to have died during the study (hazard ratio [HR] 0.9, 95% confidence interval [CI] 0.84 to 0.96).

People who ate spicy food more than two days a week were about 14% less likely to have died during the study (HR 0.86, 95% CI 0.8 to 0.92) but the difference between eating spicy food once or twice a week and more often was small enough that it might be down to chance.

People who ate food containing fresh chilli pepper more than six times a week were less likely to die than those who ate dried chillies this frequently.

The researchers looked at the causes of death and found people who ate spicy food more often were less likely to die from cancer, heart disease or respiratory (lung) diseases. However, the amount of spicy food made little difference to the chances of dying from stroke, diabetes or infections.

How did the researchers interpret the results?

The researchers said their results showed “significant inverse associations” between eating spicy food and dying of any cause or of some specific causes, meaning that people who ate spicy food were less likely to die of these causes.

They said the active ingredient in chilli pepper, capsaicin, has been shown to have a range of health-promoting effects, including antioxidant, anti-inflammatory and anti-cancer effects.

However, the researchers were cautious about their results. They said they could not conclude that spicy food protected against death, and that it is “essential” to carry out research in other groups of people outside China to be sure the results apply elsewhere.

They say further research could lead to evidence that will allow for updated guidelines on what people should eat for a healthy diet.

Conclusion

This large, well-designed observational study adds to the evidence that certain spices such as chilli pepper may have a beneficial effect on health. But this study does have limitations that need to be taken into account.

The study found that people in China who ate a diet that included spicy food (mainly from chilli peppers) at least once a week were less likely to die during the study period than those who ate spicy food less often. These results applied to men and women, even after taking account of factors that affect the risk of death, such as age.

The study is part of an ongoing investigation into the effect many factors have on human health, including diet.

The amount of data collected on individuals, including detailed information about their regular diet, activity levels, occupation, family health history and other factors, means the researchers have a better chance of finding an effect from specific factors in the diet.

Also, the size of the study means the researchers have enough data to show clear trends, with less likelihood the results are down to chance alone.

However, even with the amount of detail collected about people in the study, we cannot be sure other factors did not have an effect. For example, we don’t know how people cooked the chilli peppers, so we don’t know whether they may have used more or less cooking oil, or other spices, or ate more rice or other carbohydrates to “dampen down” the effect of the hot chilli.

Additionally, the diet frequency questionnaire was only completed once, at the beginning of the study, and people’s diets can change over time.

The lifestyles of people in rural China are likely to be very different from the urban populations of the UK or US. Eating some of the same foods may not have the same results if lots of other things about your life are different. The type of spicy food eaten by people in China, with different cooking techniques, may be very different from the sort of spicy foods eaten in the UK.

The study also found that drinking alcohol may reduce any positive effects of eating chilli peppers. The link between reduced chances of death and eating spicy food was weaker in people who also drank alcohol. The habit of drinking beer with curry in the UK may undermine any good news on chilli pepper.

Overall, this study adds to emerging evidence that capsaicin in chilli pepper may have a positive effect. We now need to see studies in populations outside China to be sure the findings apply to the rest of the world.

 

 
[“source-ndtv”]

New brain diet ‘slows mental decline’

New brain diet 'slows mental decline'

“Eating food rich in vitamins and minerals keeps the brain younger,” reports the Daily Express. The headline was prompted by a US study of a new diet called MIND, which appeared to slow down ageing of the brain.

The MIND diet was developed specifically to help improve brain function and reduce dementia, and is a combination of the Mediterranean diet and the blood pressure-lowering DASH diet.

Both of these diets have previously shown positive effects on cognitive decline. The researchers wanted to see if they could narrow down which elements were the most important.

An earlier study of the MIND diet found participants who stuck rigorously to the diet were 52% less likely to be diagnosed with Alzheimer’s disease.

The MIND diet involves eating “brain-healthy” foods, with particular emphasis on eating berries, such as blueberries, and green leafy vegetables, like spinach.

Unlike DASH and Mediterranean diets, MIND does not require eating lots of fruit, dairy or potatoes, or eating more than one fish meal a week.

Among the MIND diet components are 10 “brain-healthy” foods:

  • green leafy vegetables, such as spinach and kale
  • other vegetables, such as red peppers, squash, carrots and broccoli
  • nuts
  • berries, including blueberries and strawberries
  • beans, lentils and soybeans
  • wholegrains
  • seafood
  • poultry
  • olive oil
  • wine (in moderation)

And five unhealthy foods:

  • red meats
  • butter and stick margarine
  • cheese
  • pastries and sweets
  • fried or fast food

Some 960 participants, with an average age of over 80, without dementia completed food questionnaires and brain function tests each year for an average of five years.

The study found those who stuck closely to the MIND diet had brains about eight years younger than those in the study who didn’t.

While these results are encouraging, this type of study can only show an association between diet and improved brain function – it cannot prove causation. Even so, the study does lend weight to the potential benefits of eating this type of diet.

Dr Clare Walton, of the Alzheimer’s Society, told the Mail Online: “Previous research suggests that the MIND diet can reduce the risk of developing dementia, and now we see it could also slow down the cognitive decline normally seen with age.”

“It’s important that people realise there are several steps you can take to reduce your risk of dementia, in addition to a healthy balanced diet, including being physically and mentally active and not smoking.”

Where did the story come from?

The study was carried out by researchers from Rush University Medical Center in Chicago, and Harvard School of Public Health in Boston. It was funded by the National Institute on Aging.

The study was published in the peer-reviewed medical journal Alzheimer’s and Dementia.

In general, the media reported the story accurately, but the study’s limitations were not fully explained.

What kind of research was this?

This was an observational study that aimed to investigate the relationship between the Mediterranean-Dietary Approach to Systolic Hypertension (DASH) diet intervention for neurodegenerative delay (MIND) and its protective properties for cognitive decline seen with ageing.

The MIND diet is a combination of the Mediterranean and DASH (Dietary Approaches to Stop Hypertension) diets. Researchers say both diets have shown positive effects in delaying the decline in brain function in previously conducted randomised control trials.

A number of other studies have also observed slower decline in mental abilities with high consumption of vegetables and green leafy vegetables.

What did the research involve?

Older adults from Chicago were assessed annually between February 2004 and 2013 in terms of their diet and cognitive abilities. This comprised 960 residents of more than 40 retirement communities and senior public housing units. Their average age was 81.4 years, and 75% were female. Though the study spanned nine years, the average follow-up was 4.7 years.

The study participants did not have dementia at the time of enrolment into the trial and individuals with known dementia were excluded from the study.

Each participant underwent annual structured clinical evaluations and completed food frequency questionnaires, including total energy intake. The diets were scored according to how closely they followed the MIND diet.

Brain function testing was performed using 21 tests, 19 of which summarised ability in five areas:

  • episodic memory – a type of long-term memory of specific events, situations and experiences
  • working memory – short-term memory associated with reasoning, comprehension and learning
  • semantic memory – long-term memory that processes ideas and concepts not drawn from personal experience
  • visuospatial ability – ability to understand and process shapes and distances when performing specific tasks
  • perceptual speed – ability to quickly and accurately compare letters, numbers, objects, pictures or patterns

Researchers also collected information on age, smoking history, weekly physical activity, mood, BMI, hypertension history and diabetes.

Lastly, they used statistical methods to assess the relationship between the MIND diet and brain function score.

What were the basic results?

Higher MIND diet scores were associated with slower mental decline. This was true for all five mental tests, particularly for episodic memory, semantic memory and perceptual speed.

People with MIND diet scores in the top third had a slower decline than those in the bottom third, which was equivalent to being 7.5 years younger.

The results remained significant when potential outside factors (known as confounding factors) were taken into account, including hypertension, heart attack, stroke and diabetes.

How did the researchers interpret the results?

The researchers concluded that, “Higher MIND diet score was associated with slower decline in cognitive abilities”. They said that, “The MIND diet was based on the dietary components of the Mediterranean and DASH diets, including emphasis on natural plant-based foods, and limited intake of animal and high saturated fat foods.

“However, the MIND diet uniquely specifies consumption of berries and green leafy vegetables, and does not specify high fruit consumption (both DASH and Mediterranean), high dairy (DASH), high potato consumption, or more than one fish meal per week (Mediterranean).”

Conclusion

This observational study aimed to investigate the relationship between the MIND diet and its protective properties for mental decline in an older population.

The study has several strengths, including the large sample size, long observational period of up to nine years, regular annual assessment of cognitive functions, and comprehensive assessment of diet.

However, one of the main limitations is that this type of study cannot show cause and effect – it can only show an association between the diet and slower mental decline. There may be other unmeasured factors that account for the results, such as genetics, other medical conditions or medication.

It also relies on self-reported estimates of dietary intake, so there is a chance for recall and reporting bias. Also, the study population at the time of enrolment was free of dementia, so we do not know how this diet would work in people with, or at increased risk of, dementia.

Overall, the study does lend weight to following the principles of this type of diet. Find out more about reducing the risk of dementia.

 

 
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Low-fat diets ‘not the best way to lose weight’

People may find it harder to stick to a low-fat diet

“Low-fat diets are not the best way to lose weight,” the Daily Mail reports. The findings come from a new review that analysed data from more than 50 previous studies on low-fat dietary interventions involving almost 70,000 adults.

The study aimed to see how low-fat diets measured up to comparison diets for achieving long-term weight loss, defined as a year or more.

The findings were mixed. There was evidence from a large number of trials that low-carb diets were better for weight loss than low fat – helping to achieve 1.15kg more weight loss after one year.

However, low-fat diets still worked, and consistently resulted in about 5.41kg more weight loss than if the person continued with their usual diet.

But a potential limitation of this latest research is that the individual trials varied greatly in their study populations (many had varied chronic diseases), as well as the constituents of the low-fat and comparison diets, and the ways these diets were encouraged or monitored.

Also, it is difficult to know how compliant people may have been to the diets they were assigned to. This makes it harder to tease out the specifics of the best diet, as many different methods were pooled to find the overall pattern.

Losing weight through diet alone can be difficult. Regular exercise can increase your chances, as well as bring about other health benefits.

The NHS Choices Weight loss plan provides both dietary and exercise advice that can lead to sustainable long-term weight loss.

Don’t forget about fibre

In the thousands of words written about low-fat diets versus low-carb diets, it can be easy to overlook the usefulness of fibre for helping you lose weight.

The advantage of fibre is it can keep you feeling fuller for longer, so you are more likely to stick to your recommended calorie intake. Most people in the UK eat only about 18g of fibre a day, but should aim to eat at least 30g.

You should increase your fibre intake gradually, as a sudden increase can cause cramps and constipation. Also make sure to drink plenty of water – aim for 1.2l a day – to avoid cramps and constipation.

Read more about how to increase your fibre intake

Where did the story come from?

The study was carried out by researchers from Harvard Medical School, Harvard School of Public Health, Brigham and Women’s Hospital, and Boston Children’s Hospital in the US. Funding was provided by the US National Institutes of Health and the American Diabetes Association, which had no role in the study.

One of the authors of the study reported receiving research support from the California Walnut Commission and Metagenics, a company that sells dietary supplements.

The study was published in the peer-reviewed medical journal, The Lancet Diabetes and Endocrinology.

While some of the headlines were somewhat simplistic, the UK media generally covered the new research accurately and gave good balance to the discussion. For example, the reporting included advice that guidance should perhaps focus on portion sizes and the need to limit processed foods, rather than focusing specifically on nutrient groups like fats, carbs or protein.

Coverage also included expert recommendations suggesting preventing weight gain in the first place by better informing people about healthy diet and exercise. Of course, you can do both, pursuing a long-term prevention strategy while doing your best to deal with the immediate consequences.

What kind of research was this?

This was a systematic review that searched the literature to identify randomised controlled trials where people had been allocated to a low-fat diet or any comparison diet. The results of these studies were then pooled in a meta-analysis to look at the overall effects of low-fat diets.

The researchers discuss how the optimal nutrient balance of calories coming from fat, protein and carbohydrate to achieve long-term weight loss has been debated for decades.

Low-fat diets have been popular because of the far greater proportion of calories contained in fat, compared with the same weight of protein or carbohydrate.

However, the researchers say trials don’t consistently show that low-fat diets actually achieve more long-term weight loss than other diets. This review therefore aimed to pool the evidence to see how different dietary interventions matched up against each other.

This review has strengths, as it only included randomised controlled trials, which are the best way of looking at the effectiveness of an intervention because the participants are randomly allocated to the diet.

Studies of dietary patterns are often observational. While these can look at associations between diet and outcome, as the people choose the diet themselves, you can never be sure other health and lifestyle factors aren’t influencing the outcome.

What did the research involve?

This review searched literature databases for randomised controlled trials in adults comparing a low-fat diet with any diet of higher-fat contribution, including the person’s usual diet. Only trials that measured long-term weight change over at least a year were included.

They excluded studies where the comparison arm was not a diet, such as exercise or weight-loss medication. They also excluded studies featuring dietary supplements or meal replacements, although studies that had additional dietary changes alongside the low-fat intervention (such as boosting fruit and veg intake) were allowed.

The main outcome examined was the average change in body weight from the study start to one year or greater.

A total of 53 trials, involving 68,128 adults, met the inclusion criteria, most of which (37) came from the US or Canada. Just over a third of the trials (20) included people with specific conditions or chronic diseases, including breast cancer, diabetes and heart disease.

About two-thirds of the trials (35) had weight loss goals with the dietary intervention, but the remainder either had no weight loss target or were just aimed at weight maintenance.

Most trials (27) were only one year in duration. However, it’s not certain whether the interventions lasted this long, or just the follow-up.

The low-fat diets ranged from very low (≤10% calories from fat) to moderate fat intake (≤30% calories from fat). Comparison diets were varied and included moderate-to-high fat intakes, or other interventions, such as low carbohydrate.

The trials also varied in how they controlled the diets in their study. For example, some just gave instructions or information leaflets, while others actually provided the food.

What were the basic results?

All 68,128 adults across all trial arms lost an average (mean) 2.71kg of weight after an average of one year follow-up. The average weight loss in the 35 trials that had weight loss goals was 3.75kg.

The pooled results of 18 trials found low-carbohydrate diets were more beneficial for weight loss than low-fat, resulting in an average 1.15kg greater weight loss (95% confidence interval [CI] 0.52 to 1.79kg). These were all diets with weight loss goals – no trials aimed at weight maintenance or no weight loss compared low-fat with low-carb diets.

Low-fat diets resulted in significantly greater weight loss compared with usual diet:

  • eight trials with weight loss goals found an average 5.41kg (95% CI 3.54 to 7.29) greater weight loss with low-fat compared with usual diet
  • 11 trials with no weight loss goal found 2.22kg (95% CI 1.45 to 3.00) greater weight loss with low fat
  • three trials aiming at weight maintenance found 0.70kg (95% CI 0.52 to 0.88) greater weight loss with low fat

There was no significant difference when comparing the weight loss achieved with low-fat compared with high-fat diets, regardless of weight loss goal.

Overall, when pooling all the trials, regardless of comparator, there was no significant difference in weight loss between the low-fat diet and the comparison arms in trials aiming at weight loss.

However, for the trials with weight maintenance or no weight loss goals, low-fat diets did result in significantly greater weight loss than the comparator (1.54 and 0.70 kg, respectively).

How did the researchers interpret the results?

The researchers concluded that, “These findings suggest that the long-term effect of low-fat diet intervention on body weight depends on the intensity of the intervention in the comparison group.

“When compared with dietary interventions of similar intensity, evidence from RCTs [randomised controlled trials] does not support low-fat diets over other dietary interventions for long-term weight loss.”

Conclusion

This review has aimed to answer the question of whether low-fat diets result in any greater weight loss compared with other diets, as has often been speculated. It showed they didn’t. Most diets worked, and the low-fat ones weren’t particularly better than the rest.

The systematic review design has many strengths. It has identified a large number of studies, with almost 70,000 participants, all of which were randomised controlled trials. This should balance out any non-diet-related health and lifestyle characteristics between participants. It also only included trials of at least one year’s duration to look at longer-term effects on weight loss.

However, it is worth taking time to consider the results before potentially jumping to the conclusion that a low-fat diet is of no benefit and eating as much fat as you like is a healthy option.

The review found no difference in the effect of a low-fat diet compared with a high-fat diet. But it did consistently find changing to a low-fat diet resulted in significantly greater weight loss when continuing with the person’s usual diet, regardless of whether the person was trying to lose weight or not.

The review did, though, find evidence from a large number of weight loss trials to suggest low-carbohydrate diets may be of more benefit than low fat. Unfortunately, there were no trials available to see whether this held when no weight loss goal was intended, but it is possible the same effect may be seen regardless of aim.

But interpreting this – particularly if trying to inform someone of their likely weight loss when following a particular diet – is difficult when variations across the trials included are considered.

These were all randomised controlled trials – which is a definite plus point – but they were still diverse in many ways. The study populations varied greatly. For example, some included men or women, some just overweight or obese people, and others had people with varied chronic diseases or health conditions.

The components of the low-fat and comparator interventions, and the ways these diets were encouraged or monitored, was also very different across trials.

There are many unknowns. For example, what were the other constituents of these diets – such as fruit and vegetable intake – particularly when it was the person’s usual diet? Also, were there any specifications about what types of fat where being eaten, whether saturated fats or even trans fats, or “healthier” mono- or polyunsaturated fats?

Because of the variability in the trials, it is difficult to give a definitive answer about whether a low-fat or low-carb diet is going to help any individual lose more weight. It is likely to be overall components of the diet, and the total energy intake balanced against physical activity, that has an effect.

To lose weight, essentially we need to take in less energy, in the form of calories, than the energy we’re using up in daily activity. We need fats, carbohydrates and protein in our diet, and following a diet that completely cuts out one of these groups is unlikely to be beneficial to our health or help sustain a healthy weight in the long term.

An important goal is finding a reduced calorie diet that you actually enjoy eating. That way, you are more likely to stick to it. A healthy dietary pattern should include lots of fruit and vegetables and lower amounts of sugar, salt and saturated fats, combined with regular exercise.

 
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Do potatoes reduce stomach cancer risk?

Do potatoes reduce stomach cancer risk?

“Eating lots of potatoes will reduce your risk of getting stomach cancer,” according to enthusiastic media reports that seized on the UK’s love affair with the spud.

The mouth-watering headline followed the publication of a large Chinese review into the link between diet and stomach cancer, which involved 76 studies and 6.3 million people across several countries.

However, the news reports were perhaps a little hasty in their conclusions – the study didn’t find any specific link between eating potatoes and a lower risk of stomach cancer.

Stomach cancer is one of the most common cancers, accounting for almost 10% of cancer deaths. Research suggests some foods may help protect against stomach cancer, while others may increase the risk of getting it.

The media focus on potatoes seems to have come from the link researchers found between the cancer and white vegetables in general, such as potatoes, cabbage, onions and cauliflower.

The study found eating lots of different types of fruit, white vegetables and vitamin C was associated with a lower risk of stomach cancer.

A high intake of fruit was associated with a 7% reduction in stomach cancer. White vegetables were associated with a 33% lower risk. Meanwhile, a diet high in pickled vegetables, processed meats like sausages, salted foods and alcohol was associated with an increased risk.

Although it has several limitations, this large review will contribute to the growing body of evidence informing the dietary associations with stomach cancer.

However, it is not possible to give any firm conclusions based on this review alone. It is certainly not possible to say at this stage that eating potatoes will reduce your risk.

Where did the story come from?

The study was carried out by researchers from Zhejiang University in China, and was funded by the Chinese National Natural Science Foundation and the Natural Science Foundation of Zhejiang Province.

It was published in the peer-reviewed European Journal of Cancer.

The media seems to have gone with the slant that eating potatoes will decrease your risk of stomach cancer.

But this was not a specific finding of this review, which actually found a reduced risk of stomach cancer was associated with a higher consumption of “white vegetables”.

White vegetables include potatoes, as well as cabbage, cauliflower and onions. The review did not find any link at all when it looked specifically at potatoes.

What kind of research was this?

This systematic review aimed to pool the results of published prospective cohort studies that examined whether individual dietary factors are associated with stomach cancer risk.

As the researchers say, stomach (gastric) cancer is the fourth most common cancer in men and the fifth most common cancer in women worldwide, and counts for just under 10% of the deaths from cancer.

Dietary factors are believed to play a role in stomach cancer risk. Many previous observational studies have looked into this, including the large European Prospective Investigation into Cancer and Nutrition (EPIC) study.

The researchers say these studies suggest that processed meat may slightly increase risk, while a higher consumption of fruit and veg may decrease risk.

A systematic review is the best way to identify all published research on a given question and summarise what this evidence suggests.

Singling out individual dietary factors associated with health outcomes is challenging, as other dietary and lifestyle factors play a part, and it can be difficult to remove their effects.

Usually, drawing firm conclusions about what causes a particular disease requires drawing together a wide range of different types of evidence.

What did the research involve?

The researchers reviewed several literature databases to identify prospective cohort (observational follow-up) studies published up to the end of June 2015.

Eligible studies had to have looked at any dietary exposure (food, drinks or nutrients) and examined the risk of stomach cancer as the outcome.

Relevant studies were assessed for quality and two researchers independently extracted data from the studies to reduce the risk of error.

In total, 76 studies met the inclusion criteria, all of which were rated as being of moderate to high quality. These studies had followed a total of 6,316,385 people for 11.4 years, on average, and identified 32,758 new cases of stomach cancer over this period.

Thirty-seven of the studies were conducted in Europe, 11 in the US, 21 in Japan, four in China and three in Korea. The diets they were examining varied widely, from alcohol and salted foods to green tea and ginseng. The researchers pooled studies looking at the same food or food type to give an overall result.

What were the basic results?

Looking at studies examining fruit and vegetables, the results of 22 studies were pooled in an analysis of total vegetable consumption. No link was found with stomach cancer.

Meanwhile, 30 studies of total fruit consumption found a higher intake of fruit was associated with a 7% reduction in stomach cancer (relative risk [RR] 0.93, 95% confidence interval [CI] 0.89 to 0.98).

There was no association with stomach cancer for many of the specific fruits and vegetables examined. However, there were significant links with a few:

  • white vegetables were associated with a 33% decrease in risk (RR 0.67, 95% CI 0.47 to 0.95; data came from six studies)
  • pickled vegetables were associated with an 18% increase in risk (RR 1.18, 95% CI 1.02 to 1.36; data came from 20 studies)
  • tomatoes were associated with an 11% increase in risk (RR 1.11, 95% CI 1.01 to 1.22; data came from five studies)
  • spinach was associated with a 21% increase in risk (RR 1.21, 95% CI 1.01 to 1.46; data came from five studies)

Interestingly enough, despite the media focus on potatoes, no significant link was found between potatoes and stomach cancer (RR 0.93, 95% CI 0.82 to 1.06; seven studies).

Looking at other food types, significantly increased risk was found with:

  • processed meat (13 studies)
  • salted fish (11 studies)
  • high-salt foods (12 studies)
  • salt (8 studies)
  • alcohol (24 studies)
  • beer (13 studies)
  • liquor (12 studies)

A few studies looked at the effects of specific nutrients. The one significant result to come out of these analyses was that vitamin C was found to reduce risk by 11% in a pooled analysis of five studies (RR 0.89, 95% CI 0.85 to 0.93).

Where there was data available to examine the quantities of a specific food or drink needed to have an effect, the researchers found significant links for:

  • total fruit – 5% reduced risk per additional 100g a day
  • citrus fruit – 3% reduced risk per additional 30g a day

There weren’t, however, significant dose links with white vegetables or vitamin C. If a factor dose directly affects risk, researchers would expect to see what they call a dose response – meaning the more fruit you eat, for example, the more your risk changes.

There were also significant dose links for:

  • salted fish and high-salt foods (4% and 10% increase for each item per week, respectively)
  • salt (12% increase per 5g a day)
  • alcohol (5% increase per 10g a day)

How did the researchers interpret the results?

The researchers concluded that, “This study provides comprehensive and strong evidence that there are a number of protective and risk factors for gastric cancer in diet.”

They say their findings “may have significant public health implications with regard to prevention of gastric cancer, and provide insights into future cohort studies and the design of related clinical trials.”

Conclusion

This systematic review has gathered and summarised the results of prospective cohort studies published to date that have examined links between specific dietary items and the risk of stomach cancer.

The review has many strengths, including the large number of studies that have been reviewed and quality assessed, the large sample size, and extensive analyses carried out by individual food type.

But there are various points to note when interpreting these results. The media attention focused on potatoes and how we should eat these to reduce the risk of stomach cancer – this was not a finding of this study. It presumably comes from the decreased risk found with white vegetables.

However, exactly what white vegetables this included was not specified. Studies that specifically examined potatoes found no link with stomach cancer.

Also, researchers weren’t able to say how many white vegetables should be eaten to have a preventative effect. The researchers would expect to find this sort of link if a specific food is affecting the risk of stomach cancer.

Eating lots of fruit and vitamin C were also associated with a lower risk. But, again, while researchers could say each 100g increase in fruit a day was associated with a decreased risk, no dose response was found with vitamin C.

Given the varied results for fruit and vegetables – overall and by specific type – it is difficult to give specific advice, other than that the findings generally support advice to eat a healthy, balanced diet with plenty of fruit and vegetables.

While all the studies were rated to be of moderate to high quality, they varied widely in the population assessed, follow-up time and the main food item being examined.

There are many unknowns that could impact on the strength of the evidence found by the individual studies. This includes the methods of assessing dietary intake and over what period this was examined, how cancer outcomes were assessed, or whether researchers adjusted for other health and lifestyle factors that may influence the results.

For example, smoking is an established risk factor for stomach cancer. Smoking – or not smoking – may be associated with other “healthy” or “unhealthy” dietary habits.

Generally, a diet high in fruit – and possibly certain vegetables – has for some time been recognised to potentially decrease the risk of stomach cancer.

The World Cancer Research Fund published a similar review in 2007, concluding there was evidence to suggest that eating more fruit, non-starchy vegetables, and allium vegetables such as onions probably reduced stomach cancer risk, while salted and salty foods probably increased risk. At that point, there was not enough evidence to assess the effects of potatoes, vitamin C, or alcohol on stomach cancer risk.

This large study will contribute to the body of evidence informing the dietary associations with stomach cancer. However, it is not possible to give any firm conclusions based on this review alone. It certainly should not be advised that eating potatoes will decrease your risk of stomach cancer.

 
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A potato-rich diet before pregnancy could up diabetes risk

The researchers speculated that potatoes could disrupt the body’s metabolism

“Eating potatoes before pregnancy increases risk of diabetes,” The Daily Telegraph reports. Researchers found a small, but significant, increase in gestational diabetes risk in mothers who reported eating a potato-rich diet before their pregnancy.

Gestational diabetes is caused by raised blood glucose levels during pregnancy. It doesn’t usually cause any symptoms, but can cause complications if left untreated.

The condition does not usually pose a problem for women in England, as diabetes can be routinely screened for. If it is diagnosed, it can normally be controlled by diet and exercise.

This latest study involved researchers in the US looking at records for 21,693 pregnancies. They found that women who said they regularly ate potatoes were more likely to have had gestational diabetes.

The researchers estimated that women who regularly ate five or more portions of potatoes a week had a 50% increase in gestational diabetes risk compared to women who ate none. While this may sound high, the overall rate of gestational diabetes in the study was reported to be 5.5%.

Researchers looked at potatoes because they have high glycaemic index (GI), so release a lot of glucose into the blood shortly after being eaten. Some experts think this might increase the chances of diabetes.

Although the study found an association between potatoes and diabetes, it cannot prove cause and effect.

There’s no need to stop eating potatoes as a result of this study. On the other hand, a little variety in the types of food you eat, with plenty of vegetables and pulses, makes it easier to get a healthy and balanced diet that includes all the nutrients you need.

Where did the story come from?

The study was carried out by researchers from the National Institutes for Health, Brigham and Women’s Harvard Medical School and Harvard TH Chan School of Public Health, and was funded by the National Institutes of Health and the American Diabetes Association. The study was published in the peer-reviewed British Medical Journal (BMJ) on an open-access basis, meaning it is free to read online (PDF, 304kb).

The Daily Mirror and the Daily Telegraph both over-stated the certainty of the results, with the Mirror referring to “type 2 diabetes” instead of “gestational diabetes”. While there are similarities between the two conditions, their causes and likely outlooks are different.
However, the Mail Online and the BBC News gave good, balanced reports.

What kind of research was this?

This is a prospective cohort study, which looked to see whether there was a link between regularly eating potatoes and the chances of having gestational diabetes. Prospective cohort studies provide useful information about links between different factors, but cannot prove that one factor causes something – in this case, that eating potatoes causes gestational diabetes.

What did the research involve?

The researchers looked at records from a large group of women in the US. They looked at how often they ate potatoes (measured in diet questionnaires every four years) and whether they’d had diabetes in pregnancy. After adjusting for other confounding factors, they looked for links between diabetes in pregnancy and eating potatoes.

They used data from an ongoing study of 116,430 nurses in the US, picking a 10-year time period from 1991 to 2001. Researchers only looked at pregnancies during that time in women who had not had gestational diabetes before, and had not been diagnosed with cancer, diabetes or heart disease at the start of the study.

As well as looking at how often they ate potatoes, the researchers also took account of how healthy their diet was overall, how much they exercised, their weight, age, ethnic group and any family history of diabetes.

They ran several different analyses of the data, to see which factors affected the chances of women getting gestational diabetes. They used the findings to calculate the chances of getting gestational diabetes if they ate potatoes once a week, two to four times a week, or five or more times a week. They also looked to see what the effect might be if women swapped two portions of potatoes a week for other healthy food, such as wholegrains, vegetables or pulses.

What were the basic results?

Women who said they regularly ate two to four portions of potatoes a week were 27% more likely to have had gestational diabetes (relative risk [RR] 1.27, 95% confidence interval [CI] 1.04 to 1.55) and women who’d eaten five portions a week or more were 50% more likely to have had gestational diabetes (RR 1.50, 95% CI 1.15 to 1.96). One portion a week may also have had an effect, but the results for this group are not statistically significant, meaning the finding may be down to chance.

The overall risk of diabetes in pregnancy was quite low. There were 21,693 pregnancies and 854 cases of gestational diabetes over the 10 years of the study. The researchers said the rate of gestational diabetes in the study was 5.5%. An increase in risk of 50% from eating five or more portions a week would mean a risk of around 8%.

The researchers calculated that swapping two portions a week of potatoes for wholegrains, vegetables or pulses would reduce the relative risk by 9%, to 12%, depending on the type of food substituted.

How did the researchers interpret the results?

The researchers make it clear that these results do not show that potatoes cause diabetes in pregnancy. However, they say the suggestion that they might is “biologically plausible” because potatoes are starchy foods and quickly digested.

They said that “findings from the current study raise concerns” about dietary guidelines in the UK and the US, which advise people to eat plenty of potatoes.

Conclusion

Although we cannot say from this study whether eating potatoes could cause gestational diabetes, it does seem worth taking seriously.

This study has a number of strengths. It’s big enough to give statistically significant results and the researchers were able to adjust their results to check for many factors which could have had an effect on women’s chances of getting gestational diabetes.

They carried out sensitivity analyses to check that no one factor was skewing the results. Also, as the researchers say, there is a possible plausible scientific reason for thinking that potatoes might increase the risk of diabetes.

However, there are drawbacks to the study. The results are based on the women’s own estimates of how often they ate potatoes, and also whether they had diabetes in pregnancy. It’s possible they may have forgotten or misreported this. We also don’t know how bad the women’s diabetes was, so we can’t tell whether eating more potatoes affects the severity of diabetes in pregnancy.

Also, most of the women in the study were white Americans, so we can’t be sure the results would apply to everyone. This is particularly important, as it is known that the risks of gestational diabetes are higher in some ethnic groups, such as black women or women of South Asian origin.

Finally, even the best observational study cannot have adjusted for all possible factors affecting the outcome. That’s why we can’t say that potatoes are the cause of the increased risk of gestational diabetes.

Further research is needed to find out more about the potential links between potatoes and gestational diabetes. But what should women do if they want to get pregnant and are worried about their risk?

Advice from Public Health England remains unchanged – people should continue to eat starchy foods, including potatoes and wholegrains, to get plenty of fibre. If you are worried about how often you eat potatoes, swapping one or two portions a week for wholegrain rice, sweet potatoes, pasta or bread means you will still be following official advice, while eating a more varied diet.

There’s no need to stop eating potatoes as a result of this study. On the other hand, a little variety in the types of food you eat, with plenty of vegetables and pulses, makes it easier to get a healthy and balanced diet that includes all the nutrients you need.

 
[“source-ndtv”]

Researchers investigate why obesity can trigger bowel cancer

Obesity has been linked to several different cancers

“Excess calories ‘turn off a hormone in the intestine that blocks colon cancer’,” the Mail Online reports.

Obesity is a known risk factor for bowel cancer (also known as colorectal cancer). There is evidence that a diet rich in processed meats, which contain the potentially cacogenic compound nitrates, increases bowel cancer risk. However, it is unclear why other high-calorie diets also increase risk.

This latest study, conducted in genetically engineered mice, found that obesity caused by a diet rich in fats or carbohydrates “silenced” a hormone called guanylin. This, in turn, led to the turning off of a receptor called guanylyl cyclase C (GUCY2C) found on cells that line the bowel. Receptors are specialised structures designed to respond to specific chemical signals.

Turning off this receptor was associated with tumour growth, as the GUCY2C receptor, when working properly, is designed to prevent abnormal cell growth. Further study confirmed this by showing that using a drug to increase production of guanylin reversed the effects of the high-calorie diet and prevented tumour growth.

The obvious question is: could a similar drug be effective in obese humans thought to be at high risk of developing bowel cancer? The simple answer is: we just don’t know yet.

It is unwise to assume that the results of an animal study will transfer over to people; we are not biologically identical.

However, the study does provide a route – looking at ways to activate the GUCY2C receptor in humans – for further, hopefully fruitful, research in the area.

Where did the story come from?

The study was carried out by researchers from Thomas Jefferson University, Duke University and Harvard Medical School, and was funded by the Harvard Digestive Diseases Center, the PA Department of Health and Targeted Diagnostic and Therapeutics, Inc, which is a biotech company.

Some of the study authors have financial interests in, and/or are employed by, Health and Targeted Diagnostic and Therapeutics, Inc.

The study was published in the peer-reviewed medical journal Cancer Research.

The Mail Online’s reporting of the study is accurate and contains an interesting interview with one of the authors of the study. However, its coverage could have made it clearer the study was in mice, not humans, as this fact was only mentioned once, halfway down the page.

What kind of research was this?

This was an experimental study in mice aiming to explore the effect of diet-induced obesity on bowel cancer (health professionals often prefer the term colorectal cancer, as the cancer can also develop outside of the bowel, such as in the rectum).

In general, it is known that being obese is linked with increased risk of colorectal cancer in humans. However, the precise biological mechanism by which obesity or high-calorie intake increases risk is poorly understood.

This animal research aimed to explore this by building on the knowledge that dysfunction of a particular receptor in the cells lining the bowel – GUCY2C receptors – is associated with colorectal cancer development in a range of animal species. In particular, loss of the bowel hormone guanylin has been observed in cases of bowel cancer, and loss of this molecule “silences” the receptor, stopping it working.

The results of such animal studies are useful for investigating links that can then be explored further. However, the results may not be directly transferable to humans.

What did the research involve?

The research involved genetically engineered mice with either a functioning or non-functioning GUCY2C receptor. At four weeks old, they were fed one of three diets:

  • lean diet (3.0 kcal/g, 12.7% from fat and 58.5% from carbohydrate)
  • high-fat diet (5.1 kcal/g, 61.6% from fat and 20.3% from carbohydrate)
  • high-carbohydrate diet (3.8 kcal/g, 10.2% from fat and 71.8% from carbohydrate)

At six weeks of age, lean mice were administered a cancer-causing chemical called azoxymethane. The resulting tumours were counted and their sizes quantified at eight weeks.

High-fat mice were given tamoxifen, an artificial hormone, every four weeks, starting at four weeks of age, to make them produce guanylin. They also received six doses of azoxymethane weekly, starting at five weeks of age. Tumours were counted and their sizes quantified at 22 weeks of age.

High-carbohydrate mice were given azoxymethane at six weeks old, every week for six weeks. Tumours were counted and their sizes quantified 12 weeks after the last azoxymethane dose.

What were the basic results?

In the mice with an intact GUCY2C receptor on their colon cells, a high-fat diet reduced the levels of guanylin hormone. This led to GUCY2C receptor silencing and allowed increased DNA damage, leading to rapid cell formation and cancer formation.

The researchers suggest that these findings show the production of tumours is associated with diet-induced obesity effects. However, a high-carbohydrate diet that increased calorie intake by approximately 40% without any weight gain also led to reduced guanylin with associated receptor dysfunction and increased cancer formation – similar to that of the high-fat diet.

The study also found that by preventing the loss of guanylin and maintaining GUCY2C receptor function, the production of tumours in the intestines almost completely stopped.

How did the researchers interpret the results?

The researchers conclude that the findings show excess calories are able to suppress the GUCY2C receptor and this links obesity to the tumour pathway in colorectal cancer. The researchers go on to suggest this may provide an opportunity to prevent colorectal cancer in obese patients through hormone replacement with the drug linaclotide.

Linaclotide is currently licensed in the UK to treat constipation in cases of irritable bowel syndrome. It is known to increase levels of guanylin.

Conclusion

This was an experimental animal study aiming to explore the possible biological mechanism by which obesity may be associated with the development of bowel cancer. The findings suggest it may be down to silencing a particular receptor – GUCY2C – located on the cells lining the bowel.

The study found that excessive consumption of fat or carbohydrate in mice was associated with loss of the guanylin hormone responsible for turning on the GUCY2C receptor. Silencing this receptor led to tumour development.

Further study confirmed this by showing that using a drug to increase production of guanylin reversed the effects of the high-calorie diet and prevented the mice developing tumours.

The findings of this study are of interest and further our understanding of a possible mechanism by which obesity and high-calorie diets may be associated with the development of bowel cancer. However, caution should be taken in transferring these results to people, as we are not biologically identical to mice.

It is also not possible to say at this stage whether, as the researchers suggest, providing a drug that activates the GUCY2C receptor could be effective in the treatment of bowel cancer in humans. However, the study does provide a route for further research in the area.

Looking at the anti-constipation drug linaclotide, known to increase the production of guanylin, would seem an obvious first step.

 
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High-flavonoid foods, like berries and apples, ‘prevent weight gain’

Flavonoids may help the body store energy as muscle and not fat

“Get fruity to get fit: Eat more berries to beat a big belly,” The Sun reports. The advice is based on the findings of a major new study looking at the effects of foods rich in the compound flavonoid, such as berries and apples, on body weight.

The researchers tracked around quarter of a million people over 24 years.

Results suggest that eating more flavonoids – specifically anthocyanins (coming mainly from blueberries and strawberries), flavonoid polymers (from tea and apples), and flavonols (from tea and onions) – was linked to less weight gain.

Every extra 10 milligrams (mg) of anthocyanins, 138mg of flavonoid polymers, and 7mg of flavanols per day, was linked to 70-100g less weight gained over four-year intervals. While this may not seem a lot, it adds up over a number of years.

An inherent limitation of this type of study design is that it cannot prove cause and effect – it can only highlight associations.

It would be unwise to take this study as advice to only eat berries or apples, as a balanced diet containing a wide variety of fruits and vegetables remains important for overall health.  Nonetheless, the study is broadly in line with more robust evidence suggesting you should consume at least five portions of fruit or vegetables a day to reduce your risk of a variety of diseases.

Age-related weight gain – the dreaded “middle-aged spread” – is common, but not inevitable.

Find out how to start losing weight

Where did the story come from?

The study was carried out by researchers from the Chan School of Public Health, Beth Israel Deaconess Medical Center, Brigham and Women’s Hospital, and Harvard Medical School, all based in Boston (US), and the Norwich Medical School, University of East Anglia (UK). It was funded by the US National Institutes of Health, and the Biotechnology and Biological Sciences Research Council (BBSRC).

Two of the authors reported that they had received grants from the US Highbush Blueberry Council. These grants were unrelated to this study.

The study was published in the peer-reviewed British Medical Journal (BMJ) on an open-access basis, so you can read it for free online.

The UK media generally reported the facts of the study accurately, but most didn’t highlight the limitations of the study design, which the researchers themselves went out of their way to do.

Importantly, the study made no guarantees that if you eat or drink more flavonoids, you’d lose weight or be more likely to be a healthy weight. People eating flavonoids might have diets that are healthier in many ways, such as being high in fibre, which could explain why they are better able to maintain a healthy weight over the long term than people reporting lower flavonoid intakes. All, some or none of the weight benefits may relate directly to flavonoids.

The Daily Mirror sensibly pointed out that although flavonoids are found in various types of chocolate and wine, the calories may counter any positive weight loss effect.

What kind of research was this?

This research combined results from three cohort studies looking at whether dietary intake of specific flavonoid subclasses (including flavonols, flavones, flavanones, flavan-3-ols, anthocyanins, and flavonoid polymers) was associated with weight change over time.

The study team describe how previous studies show that those who eat more fruit and veg are more likely to maintain a healthy weight, which is unsurprising. What is less clear is the specific mechanism by which the fruit and vegetables lead to a healthy weight, or prevent weight gain.

This study looked specifically at the flavonoids, to see whether they were the crucial weight-maintaining ingredients.

Readers should be aware that these types of studies can find associations between consumption of certain food ingredients (like flavonoids) with weight gain or other health benefits. However, they cannot prove that by increasing your consumption of flavonoids you will put on less weight than if you didn’t. A study where you randomly assign people a diet high in flavonoids for a long period of time would be needed to test this, and may not be the most practical to implement. Most people don’t follow diets given to them for long periods.

What did the research involve?

The study analysed diet and weight change information on 124,086 adult health professionals over 20 to 24 years from three cohort studies in the US: the Health Professionals Follow-up Study (HPFS), Nurses’ Health Study (NHS), and Nurses’ Health Study II (NHS II).

Self-reported change in weight was collected every two years via a questionnaire and was converted into a weight change measure spanning four-year intervals.

All participants self-reported their diet every four years using a validated, food frequency questionnaire. Foods were looked up on a US Department of Agriculture database to estimate their flavonoids content.

Information on other lifestyle habits were collected every four years via the same questionnaire. This was then incorporated into the analysis to minimise their effects, in an effort to isolate the effect of flavonoids. This adjustment of the analysis for confounders included the following variables:

  • age
  • body mass index (BMI)
  • change in smoking status
  • physical activity level
  • hours of sitting or watching TV
  • hours of sleep over the same time period

They also took into account changes in intake of the following foods/nutrients:

  • fried potatoes
  • juice
  • whole grains
  • refined grains
  • fried foods
  • nuts
  • whole-fat dairy
  • low-fat dairy
  • sugar-sweetened drinks
  • diet drinks
  • sweets
  • processed meats
  • non-processed meats
  • trans fat
  • alcohol
  • seafood
  • caffeine

Citrus juices were a main source of both flavone and flavanone intake in the study, so the researchers used non-citrus juice rather than all-fruit juice as a covariate for analyses of these two flavonoid subclasses. In additional models, they further adjusted for change in total fibre intake (g/day).

People with chronic disease at study start were excluded, due to the risk of their disease causing weight loss – messing up any link with flavonoids. This included some very common conditions like being obese (with a BMI of 30 or over) or having diabetes. This means the study group are a particularly healthy sub-group of the US general population, which is something we should bear in mind when interpreting the results.

The main analysis looked for links between four-year change in weight and change in intake of flavonoid subclasses over the same period, having adjusted for the long list of likely confounders.

What were the basic results?

Average age over the three cohorts was 36 to 49 (range 27 to 65) and over each four-year period, people gained an average of 1-2kg.

Consumption of most flavonoid subclasses (with the exception of flavones and flavanones) was associated with less weight gain among men and women aged 27-65 followed for up to 24 years.

The greatest magnitude of association was observed for anthocyanins (coming mainly from blueberries and strawberries), flavonoid polymers (from tea and apples), and flavonols (from tea and onions). Each set increase in anthocyanins (10mg), flavonoid polymers (138mg), and flavonols (7mg) was linked to 70-100g less weight gained over four-year intervals.

These associations remained statistically significant for anthocyanins and flavonoid polymers (including proanthocyanidins alone) after further adjustment for fibre intake, which was inversely associated with weight change in all three cohorts. This suggested that high anthocyanin and flavonoid polymer food sources may be associated with less weight gain through mechanisms other than fibre content.

The study repeated the analysis in those who were obese in the study and found the same links. These people had become obese while taking part in the study; obese people were excluded at the study outset.

How did the researchers interpret the results?

The researchers concluded that: “Higher intake of foods rich in flavonols, flavan-3-ols, anthocyanins, and flavonoid polymers may contribute to weight maintenance in adulthood and may help to refine dietary recommendations for the prevention of obesity and its potential consequences.”

The research team describe the magnitude of the effect as “small” but pointed out then even small decreases in weight gain may have an important public health impact. For example, they cite two studies they say suggest that “losing just 11-22lbs (5.0-10kg) is associated with a decrease in blood pressure”. Bearing in mind that the maximum difference was 100g less weight gained per four years, it would take around 200 years to achieve this.

Conclusion

This study found that people who ate more flavonoids, specifically anthocyanins (coming mainly from blueberries and strawberries), flavonoid polymers (from tea and apples), and flavonols (from tea and onions), gained less weight than those consuming less over a 24-year period. Every extra 10mg of anthocyanins, 138mg of flavonoid polymers, and 7mg of flavonols was linked to 70-100g less weight gained over four-year intervals. This isn’t a lot, but adds up over the years.

Readers should be aware that cohort studies like this can find associations between consumption of certain food ingredients (like flavonoids) with weight gain or other health benefits, but they cannot prove that by increasing your consumption of flavonoids you will put on less weight. A study where you randomly assign people a diet high in flavonoids for a long period of time would be needed to test this, and may not be the most practical to implement.

However, the results are consistent with general public health advice to eat lots of fruit and vegetables. Most people in the UK don’t eat the recommended minimum of five portions of fruit or vegetables per day, so you may benefit from eating more and a larger variety.

The study was large and long term – both big strengths, thereby increasing the reliability of the findings.

However, no study is perfect and the study authors pointed out the major limitations of their work.

Firstly, the accuracy of estimates of flavonoid content can be affected by ripeness, storage conditions, food processing, and season. This measurement error would make it less likely to find the association the study did and may underestimate the effect of flavonoids on weight gain.

The results could again underestimate true associations if people who gained weight at the beginning of a four-year period modified their diet in response, eating more fruits and vegetables (flavonoids) to lose weight (reverse causality). On the other hand, the results could overestimate true associations if people who gained weight stopped eating fruits and vegetables.

Individuals who eat more flavonoid-rich foods like fruit and vegetables may have other lifestyle or dietary habits that lead them to put on less weight. The study made many practical efforts to limit this effect, such as controlling for fibre, smoking and many other foods, but may not have completely eliminated the meddling influence of other compounds on any potential flavonoid weight link.

Hence, we must be very careful about recommending high-flavonoid foods as being beneficial to health, although consuming at least five portions of fruit or vegetables a day has significant health benefits.

A healthy diet, while beneficial, may not be enough to prevent weight gain or help you lose previously gained weight. Regular exercise is also needed.

Read more about diet and exercise and how the NHS Choices weight loss guide uses both to help you lose weight.

 

 
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Young women with high-fibre diet may have lower breast cancer risk

Eating plenty of fruit and vegetables should provide you with enough fibre

“Teenage girls who get their five-a-day cut breast cancer risk by up to 25 per cent,” the Daily Mirror reports.

A US study suggests teenagers and young women who eat a high-fibre diet based on eating plenty of fruit and vegetables have a reduced risk of breast cancer in later life.

This large and lengthy study tracked around 90,000 US female nurses over 20 years. It found that women whose dietary habits during adolescence and early adulthood placed them in the top fifth highest average fibre intake group (top quintile) were around 25% less likely to develop breast cancer compared to women in the bottom quintile.

This raises the suggestion that young women might be able to significantly lower their risk of breast cancer simply by eating more high-fibre foods, such as fruits and vegetables.

However, other associated diet and lifestyle factors may be affecting this outcome. Even if the link is with high-fibre food, it could still be down to benefits other than fibre found in fruit and veg.

If the link does exist, it’s unclear why fibre could prevent breast cancer. One speculation offered in the study is that fibres may reduce levels of circulating oestrogen, which is known to trigger abnormal breast tissue growth.

These uncertainties aside, the study is in line with recommendations to eat at least five portions of fruit or vegetables a day to reduce your risk of a variety of diseases.

Where did the story come from?

The study was carried out by researchers from Harvard T.H. Chan School of Public Health and was funded by the US National Institutes of Health and a grant from the Breast Cancer Research Foundation. One of the authors was supported by the Japan Pharmaceutical Manufacturers Association.

The study was published in the peer-reviewed medical journal Paediatrics.

For the most part, the UK media reported the story accurately, with most highlighting how fruit and vegetables could reduce breast cancer risk by one quarter in their headlines. This figure relates specifically to the breast cancer risk reduction of eating fibre in adolescence and early adult life, comparing the highest fifth of people consuming fibre with the lowest fifth. This is among the largest risk reductions reported; other risk reductions were smaller.

What kind of research was this?

This cohort study investigated whether women eating more fibre might be less likely to develop premenopausal breast cancer later in life.

The research write-up says that previous studies of fibre intake and breast cancer have almost all been non-significant – that is, they were not statistically significant and may be due to chance. However, none of them examined diet during adolescence or early adulthood – a period when the research team say breast cancer risk factors appear to be particularly important.

A cohort study measures changes over time and can highlight associations – for example, between eating lots of fibre in early life and developing breast cancer at a later age. The downsides of cohort studies are that they cannot prove cause and effect, as they involve no randomisation or blinding. People live their lives as they choose, and researchers measure and observe how this relates to the development of different conditions and diseases.

This means that other factors, such as other elements of a person’s diet and lifestyle, can influence the specific link of interest (called confounding). Researchers can take steps to lessen this risk, such as adjusting for confounders in the analysis, but it is difficult to eliminate the risk entirely.

What did the research involve?

This study analysed data from a US cohort set up in 1976 to investigate women’s health, called the Nurses’ Health Study II.

The researchers used dietary information collected from 90,534 premenopausal women via a questionnaire starting in 1991, and documented 2,833 cases of invasive breast cancer in the 20 years after. In 1998, about half of these women (44,263) also completed a questionnaire about their diet during high school (age 14 to 18) with linked data to 1,118 subsequent cases of breast cancer.

Participants were divided into quintiles (fifths) according to their dietary fibre intake and followed up with further questionnaires about their lifestyle and disease history every two years.

The analysis looked at the link between total fibre, soluble fibre and insoluble fibre consumption in adolescence and early adult life, and development of breast cancer.

The stats were adjusted for a large number of potential confounders collected through questionnaires every two years throughout the study, including:

  • age
  • race
  • family history of breast cancer (invasive or benign)
  • smoking habits
  • height
  • body mass index (BMI) at age 18
  • weight change since age 18
  • age at first period
  • how many children women had and their age at first birth
  • oral contraceptive use
  • alcohol intake
  • energy intake
  • menopausal status

What were the basic results?

Among all women, total dietary fibre intake in early adulthood was associated with significantly lower breast cancer risk – around 19% lower (relative risk [RR] for highest versus lowest quintile 0.81; 95% confidence interval [CI] 0.72-0.91).

Higher intakes of soluble fibre (RR for highest versus lowest quintile 0.86; 95% CI 0.77-0.97) and insoluble fibre (RR for highest versus lowest quintile 0.80; 95% CI 0.71-0.90) were each associated with lower breast cancer risk.

Total dietary fibre intake in adolescence was linked with lower breast cancer risk (RR for highest versus lowest quintile 0.84; 95% CI 0.70-1.01) and was borderline statistically significant, meaning it could be due to chance.

For average fibre intake during adolescence and early adult life, the RR comparing highest with lowest quintiles was 0.75 (95% CI 0.62-0.91). This is equivalent to a 25% RR reduction and is the main figure making the headlines.

How did the researchers interpret the results?

The researchers say their findings: “support the hypothesis that higher fiber [sic] intakes reduce BC risk and suggest that intake during adolescence and early adulthood may be particularly important.”

Conclusion

This large and long-term cohort study showed that women with the top fifth highest average fibre intake during adolescence and early adulthood were around 25% less likely to develop premenopausal breast cancer decades later than those in the bottom fifth.

This raises the suggestion that young women might be able to significantly lower their risk of breast cancer – the most common cancer in the UK – simply through eating more high-fibre foods such as fruits and vegetables.

However, it’s worth noting a few points before accepting these promising results at face value.

Total dietary fibre intake in adolescence alone was linked with a 16% lower breast cancer risk, but this was borderline statistically significant (p=0.04) meaning there is a 1 in 25 probability it is a chance result. The usual cut-off for saying something is statistically significant is where there is less than a 1 in 20 (p<0.05) probability it is due to chance, so it’s around the threshold.

Given that previous studies of fibre intake and breast cancer have almost all been non-significant, this should raise healthy scepticism on attributing too much importance to the adolescent element of diet.

The more reliable result came when fibre intake from adolescents and early adults were combined. This lead to a 25% reduction.

The study isn’t conclusive in saying that fibre is protective for breast cancer, although it shows a link in a large number of women. For example, women with higher fibre intake in adolescence showed signs of living healthier lifestyles generally: they were less likely to smoke, more likely to drink less alcohol, and have lower BMIs in adulthood. Although adjusted for in the analysis, these and a wide range of lifestyle factors have had a residual influence on the results.

The research team also noted that many foods high in fibre also contain many other biologically active ingredients (like flavonoids) so they couldn’t rule out the possibility these were driving the health benefits, instead of, or alongside, fibre.

The study also had a number of limitations that affect the accuracy of its measurements – for example, the fact that women reported their adolescent diet when they were middle aged (33 to 52). It is unlikely they would accurately recall their diets from 20 or so years ago. However, these inaccuracies would make it less likely to find a link, not more.

A 2010 World Cancer Research Fund report, that looked systematically at all evidence related to diet and cancer, said the evidence on fibre was limited, so no conclusions could be drawn. This report is due an update in 2016, which may include the results of this study.

Irrespective of whether fibre on its own, or foods that contain fibre in general, protect against breast cancer, the study is broadly in line with robust evidence suggesting you should consume at least five portions of fruit or vegetables a day. This can reduce your risk of developing a range of chronic diseases, such as heart disease, stroke, type 2 diabetes and obesity.

Most people in the UK don’t eat the recommended minimum of five portions of fruit and vegetables a day, so chances are you will benefit from eating more and a larger variety. Read more about how to get your five a day and how to increase the amount of fibre in your diet.

 
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