[Nutrition and colorectal cancer]

Diet plays an important role in the pathogenesis of colorectal cancer. Current prospective cohort studies and metaanalysis enable a reevaluation of how food or nutrients such as fiber and fat influence cancer risk. Based on the evidence criteria of the WHO/FAD, risk reduction by a high intake of fruit is assessed as possible, while a lowered risk by a high vegetable intake is probable. Especially raw vegetables and fruits seem to exert anticancer properties. The evidence of a risk reducing effect of whole grain relating to colorectal cancer is assessed as probable whereas the evidence of an increased risk by high consumption of refined white flour products and sweets is (still) insufficient despite some evidences. There is a probable risk reducing effect of milk and dairy products. e available data on eggs and red meat indicate a possible risk increasing influence. Stronger clues for a risk increasing effect have been shown for meat products leading to an evidence assessed as probable. Owing to varied interpretations of the data on fiber, the evidence of a risk reducing effect relating to colorectal cancer is assessed as possible or insufficient. The available data on alcohol consumption indicate a possible risk increasing effect. In contrast to former evaluations, diets rich in fat seem to increase colorectal cancer risk only indirectly as part of a hypercaloric diet by advancing the obesity risk. Thus, the evidence of obesity, especially visceral obesity, as a risk of colorectal cancer is judged as convincing today. Prospective cohort studies suggest that people who get higher than average amounts of folic acid from multivitamin supplements have lower risks of colorectal cancer. The evidence for a risk reducing effect of calcium, selenium, vitamin D and vitamin E on colorectal cancer is insufficient. As primary prevention, a diet rich in vegetables, fruits, whole grain products, and legumes added by low-fat dairy products, fish, and poultry can be recommended. In contrast the consumption of sweets, refined white flour products and meat products should be reduced.