Subjects: Behavioral health
Twenty years ago the World Health Organization recommended that people should consume at least 5 portions of fruit and vegetables per day in order to prevent cancer and other chronic diseases. The advice has become gospel pretty much ever since.
Unfortunately, a recent study by Paolo Boffetta and colleagues at Mount Sinai School of Medicine does not substantiate the claim.
The scientists analyzed 500,000 subjects from 10 countries who were enrolled in the European Prospective Investigation into Cancer and Nutrition. They concluded that consuming an extra 2 portions of fruits and veggies per day could prevent at most 2.6% of cancers in men and 2.3% of cases in women, after accounting for lifestyle factors like smoking and exercise.
Even these modest gains could have been due to the fact that people who consumed more fruit and vegetables lived healthier lives in other respects, with the latter behaviors actually accounting for the gains.
The scientists found that vegetables, which tend to have more nutrients, were more beneficial than fruits, and that heavy drinkers and smokers appeared to gain the most from increased consumption of fruits and vegetables.
In an accompanying editorial, Harvard University nutrition expert Walter Willet said the study confirmed previous findings. “Any association of intake and fruits and vegetables with risk of cancer is weak at best,” he told the BBC.
Although the link between diet and cancer seems less certain, it is becoming increasingly clear that obesity is a major risk factor for cancer. Thus to the extent that fruits and vegetables are substituted in the diet for higher calorie foods, they could still drop cancer risk via this mechanism.
The write-up appears in the Journal of the National Cancer Institute.