Eating more than five portions of fruit and vegetables every day is probably of no greater health benefit, research published this morning suggests.
While eating “five a day” is associated with a lower risk of death, especially from heart disease, going beyond five portions has no further benefit.
In an analysis of 16 studies involving more than 830,000 participants, US and Chinese researchers found the average risk of death from all causes was reduced by 5 per cent for each daily serving of fruit and vegetables.
They found that most of this reduction was due to a reduced risk of death from cardiovascular causes such as heart attack and stroke. There was no appreciable association between fruit and vegetable intake and death from cancer.
Daily threshold
In addition, the dose-response relationship levelled off once a threshold of five daily portions was reached. “For the reduction in total mortality, we found a threshold of around five servings a day of fruit and vegetables, after which the risk of death did not reduce further,” the authors say.
“Possible mechanisms might involve the availability of nutrients and the digestibility of fruit and vegetables, but further studies are needed to confirm our results.”
The meta-analysis (a study of combined previous research), published online by the British Medical Journal, conflicts with recent research suggesting that seven or more daily portions of fruit and vegetables were linked to the lowest risk of death.
Other studies have suggested a small beneficial link between fruit and vegetable consumption and a lower risk of death from cancer.
Taken together, a reduction in deaths from all causes of between 10 per cent and 30 per cent has been found in most prospective studies comparing highest with lowest fruit and vegetable consumption.
Today's research affirms current recommendations by health-promotion groups such as the Irish Heart Foundation. However, for people concerned about reducing their risk of cancer, in addition to eating adequate amounts of fruit and vegetables, close attention to factors such as obesity, maintaining adequate physical activity, quitting smoking and reducing alcohol intake is crucial.
The authors say further research is needed to see if fruit and vegetable consumption might have stronger effects on specific cancer sites, and if different types of fruit and vegetable may have specific influences on cancer risk.
