For more than two decades American and international health organizations have promoted eating five or more servings of fruits and vegetables a day as a way to prevent cancer by as much as 50 to 70 percent. A new study says the impact is much less, only about four per cent.
The eight-year study took place in 10 European countries between from 1992 to 2000. Participants ate about 400 grams of fruits and vegetables a day and the results show the diets had only a minor effect against developing cancer.
Published in the current issue of the Journal of the National Cancer Institute, the study found ''no conclusive evidence'' of a link between cancer and fruit and vegetables.The authors found a small inverse association between high intake of fruits and vegetables and reduced overall cancer risk. Vegetable consumption also afforded a modest benefit but was restricted to women. Heavy drinkers who ate many fruits and vegetables had a somewhat reduced risk, but only for cancers caused by smoking and alcohol. The authors caution against attributing any risk reduction to diet and they conclude that any cancer protective effect of these foods is likely to be modest, at best.
"In this population, a higher intake of fruits and vegetables was also associated with other lifestyle variables, such as lower intake of alcohol, never-smoking, short duration of tobacco smoking, and higher level of physical activity, which may have contributed to a lower cancer risk," they write.
During the 1990s health professionals and government officials started campaigns to encourage people to eat more fruits and vegetables to reduce the risk of many cancers. In 1991 the National Cancer Institute adopted the Five-A-Day program which promoted increasing the average consumption of fruits and vegetables to at least five servings a day. People with family histories of cancer were told these diets could help prevent their chances of getting cancer by as much as 50 percent. Cancer patients were taught to eat more fruits and vegetables to support their recovery.
In recent years those recommendations have been questioned in several studies.