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Can exercise offset some of the harms of regular drinking?

NHS Choices - Behind the Headlines -

"Adults who booze regularly but exercise for five hours a week are no more likely to die than teetotallers," the Mail Online reports.

A study suggests exercise may compensate for some, but certainly not all, of the harms associated with excessive alcohol consumption. This latest study looked at deaths from cancer and cardiovascular disease, as well as premature death in general (usually judged to be dying before the age of 75).

Researchers looked at around 10 years' worth of national survey data from UK adults aged over 40. Unsurprisingly, they found links between all-cause and cancer mortality in inactive people. But they also found increasing levels of physical activity generally removed the association with drinking habits. In fact, occasional drinking was associated with a significant reduction in all-cause mortality for the most active of people.

Although the study had strengths in its large sample size and regular follow-up, we can't be sure that any links observed were solely down to the interaction between alcohol and exercise. For example, people who are physically active may also avoid smoking and consume healthy diets. It is difficult to completely control for such influences when analysing data like this.

While regular exercise may mitigate against some of the harms associated with excessive alcohol consumption it certainly won't make you immune. Many world-class sportspeople, such as George Best and Paul Gascoigne, have had both their careers and lives blighted by drinking.

 

Where did the story come from?

The UK-based study was carried out by an international collaboration of researchers from Canada, Australia, Norway and the UK. The health surveys on which the study was based were commissioned by the Department of Health, UK. Individual study authors also reported receiving funding from the National Health and Medical Research Council and University of Sydney. 

The study was published in the peer-reviewed British Journal of Sports Medicine. 

The media coverage around this topic was generally overly optimistic, highlighting that by exercising, individuals can completely undo the harm caused by excessive alcohol consumption, which is untrue.

In particular, the Mail Online claimed "Adults who booze regularly but exercise for five hours a week are no more likely to die than teetotallers" which could send out the wrong message to the public.

 

What kind of research was this?

This cohort study analysed data from British population-based surveys: Health Survey for England (HSE) and the Scottish Health Survey (SHS) to investigate whether physical activity is able to moderate the risk between alcohol consumption and mortality from cancer and cardiovascular diseases.

Cohort studies like this are useful for assessing suspected links between an exposure and outcome. However, there are potentially other factors that have a role to play in such associations and therefore the study design doesn't allow for confirmation of cause and effect.

 

What did the research involve?

The researchers collected data on 36,370 men and women aged 40 or above from Health Survey for England (1994; 1998; 1999; 2003; 2004; and 2006) and the Scottish Health Survey (1998 and 2003). Among other things, the participants were asked about their current alcohol consumption and physical activity.

Alcohol intake was defined by six categories (UK units/week):

  • never drink (lifetime abstainers)
  • ex-drinkers
  • occasional drinkers (haven't drank anything in past seven days)
  • within (previous) guidelines: <14 units (women) and <21 units (men)
  • hazardous: 14-15 units (women) and 21-19 units (men)
  • harmful: >35 (women) and >49 (men)

Frequency and type of physical activity in the past four weeks was questioned and converted into metabolic equivalent task-hour (MET-hours, which are an estimate of metabolic activity) per week according to national recommendations:

  • inactive (≤7 MET-hours)
  • lower level of active (>7.5 MET-hours)
  • higher level of active (>15 MET-hours)

The surveys were linked to the NHS Central Register for mortality data and the participants were followed up until 2009 (HSE) and 2011 (SHS). There were 5,735 recorded deaths; deaths from cancer and cardiovascular disease were of most interest for this study.

The data was analysed for associations between alcohol consumption and the risk of death from all-causes, cancer and cardiovascular disease. The results were then analysed according to levels of physical activity.

Potential confounders (such as sex, body mass index and smoking status) were controlled for.

 

What were the basic results?

Overall, the study found a direct link between all levels of alcohol consumption and risk of cancer mortality. It also found that increasing levels of physical activity reduced this association with cancer mortality, and also reduced the link with death from any cause.

  • In individuals who reported inactive levels of physical activity (≤7 MET-hours), there was a direct association between alcohol consumption and all-cause mortality.
  • However, in individuals who met the highest level of physical activity recommendations a protective effect of occasional drinking on all-cause mortality was observed (hazard ratio: 0.68; 95% confidence interval (CI): 0.46 to 0.99). It should be noted that this result just skimmed the cut-off point for statistical significance.
  • In this high activity group, there was no link between all-cause mortality and alcohol consumption within guidelines, or even hazardous amounts, but the risk was still increased for those drinking harmful amounts.
  • The risk of death from cancer increased with the amount of alcohol consumed in inactive participants, ranging from a 47% increased risk for those drinking within guidelines to 87% increased risk for those with harmful drinking.
  • In people with higher activity levels (above 7.5 MET hours) there was no significant link between any amount of alcohol consumption and cancer mortality.
  • No association was found between alcohol consumption and mortality from cardiovascular disease, although a protective effect was observed in individuals who reported the lower and higher levels of physical activity (>7.5 MET-hours) and (>15 MET-hours) respectively.

 

How did the researchers interpret the results?

The researchers concluded "we found evidence of a dose–response association between alcohol intake and cancer mortality in inactive participants but not in physically active participants. [Physical activity] slightly attenuates the risk of all-cause mortality up to a hazardous level of drinking."

 

Conclusion

This study aimed to explore whether physical activity is able to moderate the risk between alcohol consumption and mortality from cancer and cardiovascular diseases. It found that increasing levels of physical activity reduced the association for death from both all-causes and cancer.

This study has strengths in its large sample size, comprehensive assessments and long duration of follow-up. The findings are interesting, but there a few points to bear in mind:

  • As the authors mention, cohort studies such as this are unable to confirm cause and effect. Though the researchers have tried to account for various potential health and lifestyle confounding variables, there is the possibility that others are still influencing the results. A notable one is dietary habits which weren't assessed. Also, for example, the former drinkers may have quit due to other health issues which may have introduced bias.
  • The study was unable to look at binge drinking levels of alcohol consumption which would have likely had important health implications.
  • Additionally, there is always the possibility with self-reported surveys that the participants either under or over-reported their drinking habits which can increase the chance of misclassification bias.
  • Though having a large sample size, fewer people reported harmful drinking levels, so links within this category may be less reliable.
  • The study has only looked at the link between alcohol and actually dying from cancer or cardiovascular disease. Links may be different if they looked at associations between alcohol and just being diagnosed with cancer or heart disease, for example.
  • The study is also only representative of adults over the age of 40.

Overall, maintaining a healthy lifestyle seems to be the best bet for reducing the risk of any chronic disease, be it through physical activity, balanced diet or reasonable alcohol consumption.

Current alcohol recommendations for both men and women are to drink no more than 14 units per week.  

Links To The Headlines

How exercise undoes the harm from drinking: Adults who booze regularly but exercise for five hours a week are no more likely to die than teetotallers. Mail Online, September 8 2016

Two hours a week of exercise could offset the dangers of alcohol. The Daily Telegraph, September 8 2016

Exercise can cut risk from alcohol-related diseases, study suggests. The Guardian, September 8 2016

Links To Science

Perreault K, Bauman A, Johnson N, et al. Does physical activity moderate the association between alcohol drinking and all-cause, cancer and cardiovascular diseases mortality? A pooled analysis of eight British population cohorts. British Journal of Sports Medicine. Published online August 31 2016

Fasting diet may help regenerate a diabetic pancreas

NHS Choices - Behind the Headlines -

"The pancreas can be triggered to regenerate itself through a type of fasting diet, say US researchers," BBC News reports.

Research in mice found a low-calorie diet may help in cases of type 1 and type 2 diabetes.

The pancreas is an organ that uses specialised cells known as beta cells to produce the hormone insulin, which the body uses to break down sugars in the blood (glucose).

In type 1 diabetes the pancreas stops producing insulin. In type 2 diabetes either not enough insulin is produced or cells in the body fail to respond to insulin (insulin resistance).

Mice were fed for four days on a low-calorie, low-protein and low-carbohydrate but high-fat diet, receiving half their normal daily calorie intake on day one, followed by three days of 10% of their normal calorie intake.

Researchers repeated this fast on three occasions, with 10 days of refeeding in between. They then examined the pancreas.

They found in mice modelled to have both type 1 and type 2 diabetes, insulin production was restored, insulin resistance was reduced, and beta cells could be regenerated. Early lab study involving human cell samples showed similar potential.

These are promising results, but further studies are needed to validate these findings in humans.

If you have either type 1 or type 2 diabetes, you shouldn't attempt a fasting diet without first seeking medical advice. A sudden change in your calorie intake could have unpredictable effects and lead to complications.

Where did the story come from?

The study was carried out by researchers from the University of Southern California and the Koch Institute at the Massachusetts Institute of Technology (MIT) in the US, and the IFOM FIRC Institute of Molecular Oncology in Italy.

It was funded by grants from the US National Institutes of Health (NIH) and the US National Institute on Aging (NIA).

The study was published in the peer-reviewed journal, Cell. It's available on an open access basis and is free to read online (PDF, 6.74Mb).

The UK media coverage of the research is generally accurate. BBC News provided useful advice from one of the authors, Dr Longo, who cautioned: "Do not try this [fasting] at home. This is so much more sophisticated than people realise". 

What kind of research was this?

This animal study examined whether a diet mimicking fasting cycles is able to promote the generation of new pancreatic beta cells in a mouse model of diabetes.

Beta cells are found in the pancreas. The cells' primary function is to store and release insulin in response to changes in blood glucose concentration.

In people with diabetes, the beta cells are either destroyed by the person's own immune system (type 1) or are unable to produce a sufficient amount of insulin (type 2).

Beta cells are reported to be highly sensitive to the availability of nutrients. The researchers wanted to see whether prolonged fasting and refeeding could regenerate pancreatic cells.

Animal studies like this one are useful early-stage research to help better our understanding of cellular mechanisms.

However, the human body has complex biology and we're not identical to mice, so further studies would be needed to see whether the same effects are observed in humans.

What did the research involve?

The first phase of the study involved male mice aged 10-16 weeks, some of whom had injections of a chemical to destroy their beta cells to mimic type 1 diabetes. Others were genetically bred to have type 2 diabetes, and normal mice acted as controls.

The researchers put the mice on a four-day fasting regimen consisting of a low-calorie, low-protein, low-carbohydrate and high-fat (FMD) diet.

They were fed 50% of their standard calorie intake on day one, followed by 10% of their normal calorie intake on days two to four.

At the end of the four days, the mice were fed regularly for up to 10 days to ensure they regained their body weight before the next fasting cycle. They underwent three dietary intervention cycles.

Blood glucose measurements were taken regularly. Pancreatic cell samples were taken to look at gene activity and investigate whether there were any changes.

The second phase of the study involved analysing human pancreatic cell samples collected from people with type 1 diabetes. 

Researchers also recruited healthy human adult volunteers without a history of diabetes, who underwent three cycles of a similar five-day fasting regimen. The blood samples from these people were applied to the cultured pancreatic human cells.

What were the basic results?

In the mouse model of type 2 diabetes, after the FMD cycles insulin secretion was restored and insulin resistance was reduced. The FMD cycles seemed to induce beta cell regeneration.

In the mouse model of type 1 diabetes, FMD cycles were able to reduce inflammation and promote changes in the levels of cytokine proteins, which may indicate the restoration of insulin secretion. There was an increase in the proliferation and number of beta cells generating insulin.

The results in the human cell samples suggested similar findings to those seen in mice. FMD cycles – that is, in blood samples from fasted individuals applied to human pancreatic cells in the laboratory – may be able to promote reprogramming of cell lineages and generate insulin in pancreatic islet cells.

How did the researchers interpret the results?

The researchers concluded that, "These results indicate that an FMD promotes the reprogramming of pancreatic cells to restore insulin generation in islets from T1D [type 1 diabetes] patients and reverse both T1D and T2D [type 2 diabetes] phenotypes in mouse models." 

Conclusion

This animal study examined whether a diet mimicking fasting cycles would be able to promote the generation of new insulin-producing pancreatic beta cells in a mouse model of diabetes.

Overall, researchers found in mice models of both type 1 and type 2 diabetes, insulin secretion was restored and insulin resistance and beta cells could be regenerated or have their function restored. Very early laboratory study on human cell samples suggested similar potential.

These results show promise, but further research is needed to validate these findings in humans.

Professor Anne Cooke, professor of immunology at the University of Cambridge, commented: "This is good science and does give promise for the future treatment of diabetes, but we need further studies to see whether this works in people as well as it has in mice."

Don't suddenly try fasting, or any other radical change to your diet, without first consulting the doctor in charge of your care. Sudden changes to your diet could cause complications.

Links To The Headlines

Fasting diet 'regenerates diabetic pancreas'. BBC News, February 24 2017

Hope for millions of diabetics as condition could be reversed with yo-yo starvation diet. Daily Mirror, February 23 2017

Fasting diet could prove the cure for type 2 diabetes. The Times, February 24 2017 (subscription required)

Links To Science

Cheng C, Villani V, Buono R, et al. Fasting-Mimicking Diet Promotes Ngn3-Driven β-Cell Regeneration to Reverse Diabetes. Cell. Published online February 23 2017

Link between herpes in pregnancy and autism is unconfirmed

NHS Choices - Behind the Headlines -

"'WOMEN infected with herpes while they are pregnant are twice as likely to have a child with autism', " The Sun reports.

The headline is prompted by a study looking at whether maternal infections during pregnancy are associated with the risk of neurological developmental disorders such as autism spectrum disorders (ASDs).

However, The Sun has focused on only one result of a much larger set of findings – none of which were able to confirm the association between maternal infections and autism in children.

The Norwegian study looked at levels of antibodies to several viruses in pregnant women, collecting samples at 18 weeks during pregnancy and after delivery. These antibodies would indicate current or previous infection or immunity following vaccination. They then followed up whether any of the women had children later diagnosed with autism.

It looked at levels of antibodies to the herpes "family" of viruses (HSV-1 and HSV-2), as well as rubella, toxoplasma gondii and cytomegalovirus (a common virus related to chickenpox).

The study initially found no association between any of the levels of antibodies during pregnancy or after delivery, and the development of ASD in boys or girls. When they performed numerous additional analyses, they found that high levels of antibodies to the HSV-2 virus during mid-pregnancy were associated with the development of ASD in boys. However, this was based on just 14 women so it not reliable.

While it is recommended to avoid the herpes virus during pregnancy due to the risks of complications, based on this evidence, autism is not one of these.

 

Where did the story come from?

The study was carried out by researchers from the US and Norway including Columbia University and the University of Oslo. It was funded by grants from the National Institutes of Health, the Jane Botsford Johnson Foundation, the Simons Foundation Autism Research Initiative, the Norwegian Ministry of Health and Care Services, the Norwegian Ministry of Education and Research and the Research Council of Norway.

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

Both The Sun and the Mail Online are arguably guilty of scaremongering and inaccuracy in their reporting of the study. They did not point out any of the limitations of the study, in particular that the results are based on such a small number of women that they could have been down to chance.

In contrast, CNN provides useful contrasting opinions from independent experts. Its coverage includes a quote from Dr David Winston Kimberlin, a professor of paediatric infectious diseases, who says "pregnant women should not be worried about HSV-2 (genital herpes) as a cause of autism based upon the findings of this single exploratory research study".

 

What kind of research was this?

This was a case-control study that wanted to look at whether maternal infections during pregnancy are associated with the risk of neurological developmental disorders such as autism spectrum disorders (ASDs).

Autism spectrum disorders are characterised by various degrees of social impairment and deficits in language and communication. The development of the condition is not well understood, but both genetic and environmental factors are thought to play a role.

Infections during pregnancy have been suggested to be a risk factor for the development of several neurological disorders such as ASD in the offspring and this study wanted to explore this hypothesis further. It hoped to understand more about disease severity and whether that was dependent on the time of infection during pregnancy.

Case-control studies are a useful way of better understanding potential links between exposure and outcome for uncommon conditions. However, the study design means that they are more prone to bias so it's important to bear in mind that other factors may have a role to play in the suspected causal relationship.

 

What did the research involve?

This study used data collected as part of the Norwegian Mother and Child Cohort Study, which recruited pregnant mothers, fathers and their children in Norway from 1999 to 2008. The study collected maternal blood samples during week 18 of pregnancy and after delivery. Questionnaires on a variety of health outcomes and conditions were sent to the mothers when their children were three, five and seven.

This Autism Birth Cohort study used data on 442 mothers of children who reported in the questionnaires that their child had been diagnosed with ASD and 464 matched controls (mothers of children without ASD). The controls were matched based on sex, birth month and birth year.

Maternal blood samples had been analysed for levels of immunoglobulin G (IgG) antibodies to Toxoplasma gondii, rubella virus, cytomegalovirus (CMV), herpes simplex virus 1 (HSV-1) and HSV-2. If the IgG antibodies were present, this would indicate that the mother had been infected with the virus at some point in her life. Higher levels or rising levels would suggest current infection or reactivation of the virus. The researchers were able to assess this by comparing the test taken mid-pregnancy with post-pregnancy.

The data was then analysed to see whether there were any links between high levels of infection and the development of ASD in the children. External confounding factors were controlled for including: maternal age at delivery, maternal smoking during pregnancy, parity (number of births) and maternal education.

 

What were the basic results?

Mothers of children with ASD were more likely to be first-time mothers. Most women in each group had antibodies to rubella because of the vaccination programme. Around half of women in each group had antibodies to HSV-1 and CMV. Fewer had antibodies to Toxoplasma (10% of mothers in each group) or HSV-2 (12% in the control group and 13% in the ASD group).

The planned series of tests found no significant differences in the presence of any of the antibodies either during mid-pregnancy or after delivery and subsequent diagnosis of ASD in boys or girls.

The researchers then performed a number of additional unplanned analyses looking at the levels of antibodies to HSV-2 and risk of ASD. When they used a high cut-off level to suggest current infection during mid-pregnancy, they found that boys were more likely to get ASD (odds ratio 2.07, 95% confidence interval 1.06 to 4.06). However, this was based on around 10 women in the ASD group and four in the control group who had "high" levels of 640AU/ml or more (precise figures not provided, our estimates are based on graphs).

With such a small sample group any association could well have been the result of chance.

 

How did the researchers interpret the results?

The researchers concluded: "This is the first study to report an association between maternal anti-HSV-2 antibody levels and risk of ASD in offspring. Our data suggest that the presence of high levels of anti-HSV-2 antibodies at mid-pregnancy increases the risk of ASD in boys.

"We speculate that ASD risk associated with high levels of antibodies to HSV-2 is not specific to HSV-2 but instead reflects the impact of immune activation and inflammation on a vulnerable developing nervous system."

 

Conclusion

This was a Norwegian case-control study that looked at whether maternal infections during pregnancy are associated with the risk of neurological developmental disorders such as autism spectrum disorders (ASDs) in their children.

The study initially found no association between any of the pathogens during pregnancy or after delivery, and the development of ASD in boys or girls.

Further investigations suggested that high levels of HSV-2 virus antibodies during mid-pregnancy were associated with increased risk of the development of ASD in boys.

The researchers suggest that the suspected risk of ASD associated with high levels of virus is not down to the HSV-2 virus itself but the impact of inflammation and the subsequent activation of the immune system on child development during pregnancy

However, while this finding has been widely reported in the media, it is based on just 14 women so is not reliable. Performing repeated unplanned analyses is bound to come up with some association in the end through sheer chance.

It is important that pregnant women do take precautions to prevent herpes infection during pregnancy, especially the third trimester, as there is a risk of passing the virus on to the baby.

More research would be needed to confirm the speculations that herpes infection during pregnancy can increase the risk of autistic spectrum disorder.  

Links To The Headlines

Pregnant women infected with herpes are ‘TWICE as likely to have a baby with autism’. The Sun, February 22 2017

Women who have a flare-up of herpes - or are infected - during early pregnancy are twice as likely to have an autistic child, study warns. Mail Online, February 22 2017

Autism link to herpes during pregnancy may be overstated, experts say. CNN, February 22 2017

Links To Science

Mahic M, Mjaaland S, Bøvelstad HM, et al. Maternal Immunoreactivity to Herpes Simplex Virus 2 and Risk of Autism Spectrum Disorder in Male Offspring. mSphere. Published online February 22 2017

Five-a-day of fruit and veg is good, but '10 is better'

NHS Choices - Behind the Headlines -

"Forget five a day, eat 10 portions of fruit and veg to cut risk of early death," The Guardian reports.

A major review found people who regularly ate 800g of fruit and veg a day – 10 portions – had a significantly lower risk of chronic diseases, such as heart disease.

Researchers looked at more than 350 studies from around the world that examined the impact of fruit and veg consumption on a range of health outcomes, such as cancer and stroke, as well as premature death.

They found eating more fruit and veg was linked to a lower risk of getting these diseases and dying early when eating up to 800g a day (around 10 portions), or 600g a day for cancer.

The specific types of fruit and veg associated with reducing the risk of developing different diseases were also listed.

So does that mean the 5 A DAY campaign that encourages people to have at least five portions of fruit and veg a day should be updated? Well, as Victoria Taylor of the British Heart Foundation argues: "There is no nutritional benefit in a guideline that is not followed."

Having five portions of fruit and veg a day was chosen by public health campaigners because it was seen as an achievable target for most people.

Dr Alison Tedstone, chief nutritionist at Public Health England, explained to the BBC that, "Whilst consuming more than five portions of fruit and vegetables a day may be desirable ... adding pressure to consume more fruit and vegetables creates an unrealistic expectation." 

Get tips on how to get your 5 A DAY.  

Where did the story come from?

The study was carried out by researchers from various academic and medical institutions in Norway, Imperial College London and Leeds University in the UK, and Harvard University and the Icahn School of Medicine in the US.

The study was funded by Olav og Gerd Meidel Raagholt's Stiftelse for Medisinsk Forskning, the Liaison Committee between the Central Norway Regional Health Authority and the Norwegian University of Science and Technology, and the Imperial College National Institute of Health Research Biomedical Research Centre. The funding body had no input into the design of the study.

The study was published in the peer reviewed International Journal of Epidemiology.

The UK media generally reported the story accurately. Some sources included quotes from independent experts, who explained 5 A DAY may not be the most optimal target, but was chosen for pragmatic reasons. 

What kind of research was this?

This was a systematic review and meta-analysis of studies looking at fruit and veg intake.

The researchers looked at fruit and veg intake and health outcomes, such as coronary heart disease, cardiovascular disease, cancer, stroke and death.

While a meta-analysis is good at summarising all research from a particular area, it's only as good as the studies it includes. Any limitations of the studies included will also be limitations of the meta-analysis.

In this case, all of the studies were prospective cohort studies. This means they are only able to show an association, and can't prove cause and effect.

What did the research involve?

The researchers analysed data from 95 prospective cohort studies that monitored people over time, and looked at fruit and vegetable intake and the risk of various diseases.

The studies were mostly from Europe and the US, but also included research from Asia and Australia. These were large studies, so there was data available for from 226,910 to 2,123,415 people for each analysis.

The relative risks for getting or dying from certain diseases was calculated for:

  • coronary heart disease
  • stroke
  • total cardiovascular disease
  • total cancer
  • all-cause deaths

The researchers looked at how each increase of 200g a day of fruit and vegetables affected the risk of disease and death.

They also estimated the number of early deaths worldwide that may be the result of eating less fruit and veg.

This was based on the assumption that the association between fruit and veg intake and the diseases was causal – in other words, how much fruit and veg a person ate was responsible for whether or not they developed a disease.

They also looked at specific fruit and vegetables and their association with risk.

What were the basic results?

Risk for each disease and death – other than cancer – was reduced with each 200g a day increase in fruit and vegetables up to 800g a day, and 600g a day for cancer.

So eating 800g a day of fruit and vegetables indicated the biggest reduction in risk.

For each 200g a day increase in fruit and veg, the risk of getting each health outcome was decreased by:

  • 8% for coronary heart disease (relative risk [RR] 0.92, 95% confidence interval [CI] 0.90 to 0.94)
  • 16% for stroke (RR 0.84, 95% CI 0.76 to 0.92)
  • 8% for total cardiovascular disease (RR 0.92, 95% CI 0.90 to 0.95)
  • 3% for total cancer (RR 0.97, 95% CI 0.95 to 0.99)
  • 10% for all-cause death (RR 0.90, 95% CI 0.87 to 0.93)

Researchers estimated that globally, a total of 5.6 million early deaths in 2013 were down to eating less than 500g a day of fruit and vegetables.

Researchers estimated that when using 800g a day as the optimal intake of fruit and vegetables, 7.8 million early deaths could have been avoided by people eating this amount.

The following specific fruit and vegetables were found to help reduce the risk of:

  • coronary heart disease – apples or pears, citrus fruit, fruit juices, green leafy vegetables, beta carotene-rich vegetables such as carrots and sweet potato, and vitamin C-rich fruit and vegetables
  • stroke – apples or pears, citrus fruit, green leafy vegetables and pickled vegetables
  • cardiovascular disease – apples or pears, citrus fruit, carrots, green leafy vegetables and non-cruciferous vegetables such as butternut squash
  • total cancer – cruciferous vegetables such as cauliflower and broccoli
  • all cause of death – apples or pears, berries, citrus fruit, cooked or raw vegetables, cruciferous vegetables, potatoes and green leafy vegetables or salads
How did the researchers interpret the results?

The researchers concluded that, "In this meta-analysis of 95 studies (142 publications), reductions in risk of cardiovascular disease and all-cause mortality were observed up to an intake of 800g/day of fruit and vegetables combined, whereas for total cancer no further reductions in risk were observed above 600g/day.

"Inverse associations were observed between intake of apples/pears, citrus fruits, green leafy vegetables/salads and cruciferous vegetables and cardiovascular disease and mortality, and between green-yellow vegetables and cruciferous vegetables and total cancer risk."

They added that, "An estimated 5.6 and 7.8 million premature deaths worldwide in 2013 may be attributable to a fruit and vegetable intake below 500 and 800g/day, respectively, if the observed associations are causal." 

Conclusion

This research supports the idea that the more fruit and veg you eat the better – at least, up to 10 portions (800g) a day.

It also suggests the number of people who die early might be reduced if they were to eat more than the current recommended guideline daily amount.

However, before we take this at face value, there are some important considerations:

  • There are likely to be many confounding factors that may have affected the results. It might be that people who eat a lot of fruit and veg are also more likely to be physically active, consume less alcohol, not smoke and be a healthy weight, or other factors that might mean better health outcomes. It's not just fruit and vegetable intake that influences the risk of getting certain diseases and dying early.
  • The study didn't look at all diseases, such as infectious or respiratory conditions, so it might be the case that eating more fruit and veg than the guideline amount is not beneficial for reducing the risk of developing all diseases.
  • The studies included might have varied in several ways – for example, the country the research was conducted in might have influenced things like the way fruit and vegetables were prepared, the different types of fruit and vegetables available, and other dietary and lifestyle factors.
  • There were few studies looking at the specific types of fruits and vegetables, so it might be there are other fruit and vegetables that are also beneficial but not listed.
  • There were considerable differences between the studies. This means that when you pool their results together, you need to view the results with some caution. This was particularly true for cancer, stroke and all causes of death.
  • As with most studies assessing diet, they are reliant on accurate self-reporting of food intake, and may not take into account changes in diet over time.

Despite these limitations, this was a strong piece of research with good statistical methodology.

If you're in the majority of the UK public who struggle to get their 5 A DAY, current advice may be a more realistic goal to aim for in the short term.

Get more advice and tips on how to make 5 A DAY part of your daily life.  

Links To The Headlines

Forget five a day, eat 10 portions of fruit and veg to cut risk of early death. The Guardian, February 23 2017

Fruit and veg: For a longer life eat 10 a day. BBC News, February 23 2017

Find five-a-day a struggle? Now experts say you should eat ten to reduce the risk of cancer or stroke. Daily Mail, February 23 2017

Forget five-a-day, eat 10 fruit and veg to prevent premature death. Sky News, February 23 2017

Eat 10 fruit and veg a day for a longer life, not five. The Daily Telegraph, February 23 2017

Links To Science

Aune D, Giovannucci E, Boffetta P, et al. Fruit and vegetable intake and the risk of cardiovascular disease, total cancer and all-cause mortality–a systematic review and dose-response meta-analysis of prospective studies. International Journal of Epidemiology. Published online February 22 2017

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