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United States Department of Agriculture

Agricultural Research Service

A Healthy Diet Decreases Cancer Risk
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Cindy D. Davis

Cancer is a disease that is dreaded by many people. Over 70 percent of human cancer is believed to be related to lifestyle. Two factors, tobacco usage and diet are especially important. Tobacco-related products are associated with about 30 percent of all cancers. However, diet is the single greatest contributor to human cancer, possibly accounting for 35-45 percent of the disease. Certain common types of cancer that appear to be influenced by diet include colon, breast, prostate and lung cancer.

Diet is comprised of various types of foods that influence cancer risk in different ways. High fat, salt, and alcohol consumption may increase your risk of developing cancer. Fiber, fruit and vegetable consumption may help prevent cancer.

The consumption of vegetables and fruit has always been seen as health-promoting. Historically, particular fruits and vegetables were thought to prevent or cure ailments ranging from headaches to heart disease. Studies spanning several decades have shown that people who eat a wide variety of vegetables and fruits have a lower incidence of many types of cancer than people who do not.

More recently, research has identified protective factors that are present in plant foods in small amounts. Some are known antioxidants (Vitamins C and E and the mineral selenium), but there are also an unknown number and combination of factors called bioactive compounds, phytonutrients or phytochemicals.

Research at the Grand Forks Human Nutrition Research Center has shown that selenium-enriched broccoli is protective against early signs of chemically-induced colon cancer in experimental animals. Both the broccoli and the particular chemical form of selenium present in the broccoli seem to be needed for the protective effect.

So what can you do? The World Cancer Research Fund and the American Institute for Cancer Research have made the following lifestyle recommendations to decrease risk of cancer:

  • First, eat a nutritionally adequate and varied diet, based primarily on foods of plant origin. In particular, eat five or more servings a day of a variety of vegetables and fruits and avoid excessive red meat consumption. Red meat should provide less than 10 percent of your total energy needs or less than 3 ounces daily.
  • Second, avoid being underweight or overweight and limit weight gain during adulthood to less than eleven pounds. It is also important to maintain physical activity. If occupational activity is low or moderate, take an hour's brisk walk or similar exercise daily.
  • Third, limit consumption of salted foods and use of cooking and table salt. Use herbs and spices to season food.
  • Finally, for those who follow the recommendations presented here, dietary supplements are probably unnecessary, and probably do not significantly reduce cancer risk.

Last Modified: 10/23/2006
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