Equally important, if not more so, is recognition of causative factors related to life style and personal habits. Perhaps the best example of this is the relationship between smoking and lung cancer. When heavy consumption of alcohol is combined with cigarette smoking, the risk for cancer of the larynx, esophagus, and mouth is greatly increased. Nutritional balance is also important in the prevention of cancer. Certain foods and food additives contain specific carcinogenic agents.
Nutritional deficiency can lower resistance and increase the risk of certain types of cancers.
Studies have shown that a relationship exists between obesity and cancer, and between dietary excess, particularly the consumption of large amounts of fats, and certain types of cancers. In general, overweight women are at increased risk for cancer of the endometrium, the gallbladder, and the kidney. Cancers associated with a high dietary intake of fat, with or without the presence of obesity, are those affecting the breast, ovary, endometrium, prostate, colon, and pancreas. Although neither saturated nor unsaturated fats are themselves carcinogenic, they act on the endocrine system and affect hormonal activity. The relationship of fat consumption to colon cancer is thought to be due to the effect of bile acids and their metabolites, which have been shown to act as tumor promoters in laboratory animals.