Those dietary factors which can affect cancer risk include food type, method of preparation, size of portion, food variety, and overall caloric balance. Current recommendations suggest that a diet which is high in fruits, vegetables, grains, and beans; and limited in meat, dairy products, and other high-fat foods is most likely to reduce cancer risk. Regular physical activity also is important. Four broad guidelines are presented by the American Cancer Society and shown in Table 1.
It is important to note that each food group contains multiple vitamins, minerals, and nutrients which are balanced in a variety of ways. The balance of these nutrients is complex and, in many cases, incompletely understood. Several studies do, however, suggest that the consumption of a single nutrient in large amounts can produce adverse affects. A diet which emphasizes fruits, vegetables, whole grains, and beans appears to be most likely to reduce cancer risk. Beans are rich in nutrients that can protect against cancer and are a low-fat, high protein alternative to meats. Saturated fat not only can increase the risk of developing cancer, but has been incriminated in the genesis of heart disease. Standard portion sizes are shown in Table 2.
In most cases, these portions are relatively small and four or five portions each day can be consumed relatively easily.
The precise role of diet and physical activity in the reduction of cancer risk remains to be defined. It is clear, however, that a high fat diet, obesity, and a sedantery lifestyle do predispose to the development of cancer, as well as to coronary artery disease. Although diet and physical activity have no proven benefit in curing an existing cancer or reducing the risk of a recurrence, cancer prevention obviously would save many lives in the absence of any advances in treatment.