Increased consumption of fruits and vegetables leads to only a small effect on cancer risk, according to a report published in the Journal of the National Cancer Institute (2010 Apr 6. [Epub ahead of print]).

To clarify the chemopreventive potential of fruits and vegetables, Paolo Boffetta, MD, of Mount Sinai Medical Center in New York City, and colleagues examined the relationship between diet and cancer in 10 Western European countries with widely varying intake of fruits and vegetables.

Researchers found that during a median follow-up of almost 9 years, an increased consumption of 7 ounces of fruits and vegetables reduced cancer risk by only 3%. Additionally, a 3.5-ounce per day increase in total vegetable intake reduced cancer risk by only 2%. However, researchers reported that analysis by gender revealed that women experience a beneficial effect of total vegetable intake.

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“Our study supports the notion of a modest cancer preventive effect of high intake of fruits and vegetables, and we can exclude chance as a likely factor,” said the study’s authors. “Nevertheless, the observed association of cancer risk overall with vegetable and fruit intake was very weak, and we cannot entirely rule out the possibility of residual confounding by these or other factors.”

According to the press release announcing the study, multiple health organizations worldwide recommend consumption of five servings of fruits and vegetables daily to ward off heart disease, cancer, and other conditions. However, no study has demonstrated conclusively that a high intake of fruits and vegetables reduces the risk of cancer.