Cancer and Lipid Nutrition

Abstract

Cancer is a major cause of mortality worldwide, and epidemiological studies have shown the influence of lifestyle -related factors, mainly nutritional factors, on its development. Compared with Western countries, Japan has had a low incidence of nutritionally related cancer, e.g., colon, breast, and prostate cancer, and a high incidence of gastric cancer. However, the dietary habits and lifestyle of Japanese have changed markedly, and the incidence of nutritionally related cancer is rapidly approaching that of Western countries. Among dietary factors, a high intake of fat is clearly associated with an increased risk of colon and breast cancer in epidemiological and experimental animal studies. Furthermore, the effects of the type of fatty acids have also been investigated in several rodent colon and breast cancer models. In general, linoleic acid enhances whereas n-3 fatty acids decrease chemical-induced colon and breast carcinogenesis. However, regarding the protective effects of n-3 polyunsaturated fatty acids on colon and breast cancer, evidence from human epidemiological studies is inconsistent. Null findings of epidemiological studies could result from several factors, and one of the important factors influencing the inconsistent results of epidemiological studies between dietary fatty acids and colon and breast cancer may be the length of follow-up. Some studies showed that a temporal change in fat intake coincided with the incidence of colon and breast cancer approximately 15 to 25 years later. It may be important to improve the Westernized dietary habits of young Japanese generations to protect against nutritionally related cancer.