Thursday February 23 2017
10-a-day is around 800g of fruit and veg
"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
- 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."
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.