Relationships of Food and Cancer

RELATIONSHIPS OF FOOD AND CANCER

Although the relationships of food and cancer have not been proved, there appear to be associations between them—both good and bad. Certain substances in foods, for example, are thought to be carcinogenic. Nitrites in cured and smoked foods such as bacon and ham can be changed to nitrosamines (carcinogens) during cooking. Regular ingestion of these foods is associated with cancers of the stomach and esophagus. High-fat diets have been associated with cancers of the uterus, breast, prostate, and colon. The regular, excessive intake of calo-ries is associated with cancers of the gallbladder and endometrium. People who smoke and drink alcohol immoderately appear to be at greater risk of cancers of the mouth, pharynx, and esophagus than those who do not.

On the positive side, it is thought that diets high in fiber help to protect against colorectal cancer. Diets containing sufficient amounts of vitamin C–rich foods may protect against cancers of the stomach and esophagus. Diets containing suffi-cient carotene and vitamin A–rich foods may protect against cancers of the lung, bladder, and larynx. Phytochemicals, substances that occur naturally in plant foods, are thought to be anticarcinogenic agents. Examples include flavonoids, phenols, and indoles, and fruits and vegetables appear to have an abundanceof them. It is advisable to eat nine or more servings of fruits and vegetables each day, including 2¹ ⁄2 cups of vegetables and 2 cups of fruit, on a 2,000-calorie diet. Legumes such as soybeans, dried beans, and lentils contain vitamins, minerals, protein, and fiber and may protect against cancer. High intakes of soy foods are associated with a decreased risk of breast and colon cancer.

Appropriate amounts of protein foods are essential for the maintenance of a healthy immune system. An immune system that has been damaged— possibly through malnutrition—may be a contributing factor in the develop-ment of cancer. Excessive protein and fat intake, however, may be a factor in the development of cancer of the colon.

The most important principle is moderation. An occasional serving of bacon or buttered popcorn or wine is not likely to cause cancer, but the regular, excessive use of carcinogenic foods may contribute to cancer. Vitamins that are thought to prevent cancer should be ingested in foods that naturally contain them. Excessive intake of vitamin supplements can be harmful. For example, abnormally large amounts of vitamin A can cause bone pain and fragility, hair loss, headaches, and liver and skin problems.