A commonly held belief is that diets containing high amounts of fruit and vegetables can significantly reduce the risk of developing a variety of cancers. However a study published online in April this year has found that consumption of fruit and vegetables leads to only a marginal decrease in overall cancer risk.
The research, which appears in the Journal of the National Cancer Institute, looked at data from the European Prospective Investigation into Cancer and Nutrition (EPIC) study which involved more than 500,000 individuals from 10 countries across Europe. At the beginning of the study, participants completed questionnaires on their lifestyle and dietary habits over the past year. The median intake of fruit and vegetables was calculated to be 335 grams per day.
Over an average follow up period of 8.7 years, 9604 men and 21 000 women developed cancer. The researchers found that a 200 gram increase in fruit and vegetable intake per day was associated with only a 3% decrease in overall cancer risk. Vegetable intake showed a stronger correlation than fruit intake with a 100 gram increase in vegetable consumption reducing cancer risk by 2% compared to 1% for a 100 gram increase in fruit. Those in the top quartile for fruit and vegetable consumption, which corresponded to at least 647 grams per day, were 11% less likely to develop cancer than those in the bottom quartile who consumed less than 226 grams per day.
The graph below shows the risk of cancer across various levels of fruit and vegetable consumption as calculated by the study.
According to lead author Dr. Paolo Boffetta of the Mount Sinai School of Medicine in Manhattan: “The bottom line here is that, yes, we did find a protective effect of fruit and vegetable intake against cancer, but it is a smaller connection than previously thought,”.
The forms of cancer that appear most strongly linked to fruit and vegetable consumption are the gastrointestinal cancers which include colorectal, stomach, oesophageal, and pancreatic cancer. According to the World Health Organization (WHO), insufficient fruit and vegetable consumption is responsible for 14% of all gastrointestinal cancers. Other cancers however have shown little or no association with fruit and vegetable consumption.
Fruits and vegetables are rich in a variety of antioxidants and phytochemicals that have shown anticancer activity in laboratory studies, however it is uncertain whether they have any clinically significant benefit at the relatively low levels that they are typically found in whole fruits and vegetables. Furthermore, other studies have found that the association between fruit and vegetable consumption and cancer risk disappears when red meat, processed meat, and fibre intake are accounted for (fibre appears to be protective against stomach and colorectal cancers while red and processed meats have been linked to an increased risk of certain cancers including pancreatic, colorectal, prostate, and breast cancer). This suggests that the inverse association between fruit and vegetable intake and cancer is more to do with a concurrent decrease in red and processed meat consumption and increase in fibre intake than any special properties of fruit and vegetables themselves.
Nevertheless, a high intake of fruit and vegetables has been linked to significant reductions in cardiovascular risk and should still form a large part of a healthy diet. The WHO recommends that individuals consume at least 400g of fresh fruit and vegetables every day (excluding potatoes) however just 35% of American adults currently consume this amount.
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