Sorry but how can this be ignored? How do ketogenic advocates answer these concerns? Colorectal cancer is one of the most common forms of cancer and is among the leading causes of cancer-related mortality. Long-term high intake of meat, particularly red meat, is associated with significantly increased risk of colorectal cancer. Food, Nutrition, and the Prevention of Cancer, a 1997 report by the World Cancer Research Fund and the American Institute for Cancer Research, reported that, based on available evidence, diets high in red meat were considered probable contributors to colorectal cancer risk.Harvard studies including tens of thousands of women and men have shown that regular meat consumption increases colon cancer risk by roughly 300 percent.12,13 Proposed mechanisms for the observed association include the effect of dietary fat on bile acid secretion, the action of cholesterol metabolites within the colonic lumen, and the carcinogenic action of heterocyclic amines produced during the cooking process, among others. In addition, high-protein diets are typically low in dietary fiber. Fiber facilitates the movement of wastes, including intralumenal carcinogens, out of the digestive tract and promotes a biochemical environment within the colon that appears to be protective against cancer.4Similarly, the Journal of the National Cancer Institute recently reported that the rate of breast cancer among premenopausal women who ate the most animal (but not vegetable) fat was one-third higher than that of women who ate the least animal fat.6 A separate study from Cambridge University, published in the Lancet, also linked diets high in saturated fat to breast cancer.5