Diet and Nutritional Risk Factors
There is a strong correlation between diet and nutritional deficiencies and many cancers. The National Academy of Sciences and others estimate that nutritional factors account for 60 percent of cancer cases in women and 40 percent in men. Cancers of the breast, colon, rectum, uterus, prostate, and kidney are closely associated with consumption of total fat and protein, particularly meat and animal fat.
Other cancers that are directly correlated with dietary factors are cancers of the stomach, small intestine, mouth, pharynx, esophagus, pancreas, liver, ovary, endometrium, thyroid, and bladder. Aflatoxin, a fungus product that is found on certain edible plants (especially peanuts), is related to human liver cancer.
Chemical Risk Factors
Chemical and environmental factors, including diet and lifestyle, may be responsible for causing 80 to 90 percent of all cancers. Theoretically, then, most cancers could be prevented if the factors that cause them can first be identified and then controlled or eliminated.
Throughout their lives, people are exposed to many chemicals and some drugs in small amounts and in many combinations unique to their culture and environment. Many chemicals and drugs are now known to cause human cancer, and many more are suspected carcinogens.
People who are exposed to chemicals either directly, such as those who work in the particular industry shown, or indirectly, such as firefighters exposed to burning objects made from chemicals, are at increased risk of developing the some cancer. The incidence of certain cancers in particular populations reflects prolonged low-level exposure to many carcinogens (chemical substances that cause cancer), cocarcinogens (substances that activate carcinogens), and promoting factors (substances that facilitate the action of carcinogens).