Nutrition and the etiology of cancer.

There is a growing body of scientific evidence that diet and nutrients play a causative role in the formation of cancer and that these factors may be amenable to active methods of prevention. It has been estimated that up to 35 per cent of cancers may be preventable by dietary manipulation. A theoretical basis for this are the direct-acting carcinogens ingested or produced in the diet, but these are not a major factor in the United States. Altered intake, metabolism, and excretion of cholesterol and bile acids by bacterial flora may be an important mechanism related to several commonly occurring cancers. Fiber and other constituents of vegetables may act as important protectors against the development of cancer. Dietary components related to cancer include dietary fat, fiber, fruits and vegetables, protein, alcohol, vitamins, and minerals. Practical advice for the primary care physician is given regarding two common food additives, saccharin and nitrites.