Cancer Health Article

Prevention

All cancers caused by cigarette smoking and heavy use of alcohol could be prevented completely. Approximately 30 percent of all cancers worldwide are due to tobacco use. Many of the skin cancers could be prevented by protection from sunlight. Certain cancers that are related to infectious exposures, such as HBV, HPV, HIV, and Helicobacter could be prevented through behavioral changes, vaccines, or antibiotics. Research shows that about 30 to 40 percent of all cancers worldwide are due to dietary factors and lack of physical activity, including obesity, and could therefore have been prevented. By making changes in regard to diet, exercise, healthy weight maintenance, and tobacco use, the incidence of cancer around the world could be reduced by 60 to 70 percent.

The Relationship between Diet, Physical Activity, and Cancer

While the exact mechanisms by which diet is related to cancer have not been completely understood, research has shown that food plays a role in cancer prevention. For example, populations whose diet includes at least five servings of fruits and vegetables a day have lower rates of some of the most common cancers. Fruits and vegetables contain many antioxidants and phytochemicals, such as vitamins A, C, and E, and beta-carotene, which have been shown to prevent cancer. It is not completely clear, however, whether it is individual phytochemicals, or a combination of them, or the fiber in fruits and vegetables that result in reduced risk of cancer.

Studies have shown the risk of prostate cancer drops for men who eat tomato products, possibly because of the phytochemical lycopene. In addition, it has been shown that colon cancer declines among those who drink green tea, which contains antioxidants and phytochemicals, and who regularly eat soy products and foods rich in selenium, an antioxidant.

Those who eat a diet low in fat, especially animal fat, also have lower cancer rates, but again it is not clear whether it is the calories, the amount and distribution of body fat, or the likelihood that a low-fat diet is high in fiber, fruits, and vegetables that is protective against cancer. High-fiber diets are thought to reduce the risk of colon cancer because the fiber helps move food through the lower digestive tract, possibly reducing the contact of any carcinogens with the bowel lining.

Scientific evidence indicates that physical activity may reduce the risk of certain cancers. This effect may be due to the fact that physical activity is associated with the maintenance of a healthy body weight. Other mechanisms by which physical activity may help to prevent certain cancers may involve both direct and indirect effects. For colon cancer, physical activity accelerates the movement of food through the intestine, thereby reducing the length of time that the bowel lining is exposed to potential carcinogens. For breast cancer, vigorous physical activity may decrease the exposure of breast tissue to circulating estrogen, a hormone that has been implicated in breast cancer. Physical activity may also affect cancers of the colon, breast, and other sites by improving energy metabolism and reducing circulating concentrations of insulin and related growth factors.

Because of these factors, recommendations of the American Cancer Society to reduce the risk of cancer include: consumption of a mostly plant-based diet, including five or more servings of fruits and vegetables each day; consumption of whole grains in preference to processed or refined grains and sugar; limited consumption of high-fat foods, particularly from animal sources; physical activity; and limited consumption of alcohol.

Nutrition for People with Cancer

People with cancer often have increased nutritional needs. As such, it is important for them to consume a variety of foods that provide the nutrients needed to maintain health while fighting cancer. These nutrients include: protein, carbohydrates, fat, water, vitamins, and minerals. Nutrition suggestions for people with cancer often emphasize eating high-calorie, high-protein foods. Protein helps to ensure growth, repair body tissue, and maintain a healthy immune system. Therefore, people with cancer often need more protein than usual.

Great progress has been made in the fight against cancer, and cancer detection and treatments have improved significantly. However, there is a disparity in cancer death rates between developed and developing countries. Between 80 and 90 percent of cancer patients in developing countries have late-stage and often incurable cancer at the time of diagnosis.

A growing body of evidence shows that simple changes in diet and lifestyle can help prevent many cancers. Further research into the exact mechanisms by which certain diets may help prevent cancer is ongoing.

SEE ALSO ANTIOXIDANTS; FUNCTIONAL FOODS; PHYTOCHEMICALS.

Gita C. Gidwani

Bibliography

American Institute for Cancer Research (1997). Food, Nutrition, and the Prevention of Cancer: A Global Perspective. Washington, DC: Author.

Cooper, Geoffrey M. (1992). Elements of Human Cancer. Boston: Jones and Bartlett.

Tortora, Gerald J., and Grabowski, Sandra Reynolds (2003). Principles of Anatomy and Physiology, 10th edition. New York: Wiley.