From Scientific American:
Despite decades of entreaties from the World Health Organization (WHO) and mothers alike to eat more fruits and vegetables, a new study has found that these dietary additions appear to do little to decrease the overall likelihood of getting cancer. The recommendation that people eat at least five servings (about 400 grams) of fruits and veggies each day, espoused by the WHO since 1990, was based on studies that found a link between higher intakes of these foods and lower risks for cancer and other diseases.
Since the 1990s, however, evidence from large studies has been mounting that the protective effects of these foods against cancer in particular might be modest—if it exists at all. (Other research has continued to show that diets high in fruits and vegetables are important for preventing conditions such as obesity and cardiovascular disease.) A new report, analyzing cancer incidence in 478,478 men and women ages 25 to 70 over more than eight years in 10 European countries, found “a very small inverse association between the intake of total fruits and vegetables and cancer risk,” the researchers concluded.