Fruits and Vegetables Not Associated With Cancer Prevention

The possibility that fruit and vegetables may help to reduce the risk of cancer has been studied for more than 30 years. Various cancers such as oral, esophageal, stomach and colon cancer are associated with an intake of fruit and vegetables.  Although some cancers have no association with fruit and vegetables, eating more of them might have some advantages in people who generally consume less of these items. This study reviewed various other studies on the topic and also suggested possibilities for further research.

In an earlier study, smokers with a low vitamin A intake from carrots, milk etc., were seen to be at a higher risk for developing lung cancer. This triggered interest in the role of fruit and vegetables in reducing the incidence of cancer. In the early nineties, it was known that “for most cancer sites, persons with low fruit and vegetable intake experience about twice the risk of cancer compared to those with a high intake.” But this conclusion soon changed to a “probable” cause within ten years as a result of bigger prospective studies. The present evaluation summarized the facts on the association of fruit and vegetable ingestion with the threat of major cancers even from large studies.

* This study reviewed various former studies, carried out across the world, on the effect of the intake of fruit and vegetables on cancer.
* The incidence of cancers of the esophagus, oral cavity, lungs, stomach, colon, breast and prostate were compared in people with and without an intake of fruit and vegetables.
* Apart from the studies reviewed on fruit and vegetables, there were also some conducted on the effect of antioxidants and supplements in diet.

* It was found that the incidence of oral, esophageal and colon cancer had a weak association with the ingestion of fruit and vegetables, but there could be other factors (like smoking, or drinking alcohol) affecting the results too.
* There was no connection between eating vegetables and fruit with stomach, lung, prostate and breast cancer.
* In general, there was no protective effect provided by fruit and vegetables against various cancers, especially in a normally well-nourished population.

Next steps
“Most of the previous research on fruit and vegetables and cancer had been conducted without a good understanding of potential mechanisms.” The author claims that understanding the cause and origin of specific cancers could help with assessing the “true protective effects” of fruit and vegetables. Also, future studies should analyze the effect of a diet rich in vegetables and fruit over a long period of time to get a clearer picture of its advantages.

Although it is unlikely that fruit and vegetables have a broad protective effect against cancer, a minimal intake is needed to prevent nutrient deficiencies. Many factors such as smoking and infections influence the onset of cancers. Until a better understanding of cancer is found, it is difficult to assess the true relation of vegetables and fruit with cancer-preventing properties. The authors concluded, “advice in relation to diet and cancer should include the recommendation to consume adequate amounts of fruit and vegetables, but should put more emphasis on the well-established adverse effects of obesity and high alcohol intakes on cancer risk.”

For More Information:
Fruit and Vegetable Intake and Overall Cancer Risk in the European Prospective Investigation Into Cancer and Nutrition
Publication Journal: British Journal of Cancer, November 2010
By T. J. Key; Oxford University, Oxford, UK

*FYI Living Lab Reports Are Summaries of the Original Research.
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