Good nutrition can prevent colon cancer

Better Nutrition (1989-90), July, 1989 by Shari Lieberman

Good Nutrition Can Prevent Colon Cancer

A high-fiber, low-fat diet, together with certain vitamins and minerals, is the best way to prevent colon cancer.

Researchers at the State University of New York at Buffalo (SUNY) have provided the most conclusive evidence to date showing the risk of colon cancer increases directly with the level of fats and calories in the diet and a person's degree of obesity.

The researchers found that the risk of colon cancer is four times grater for men with a high-fat and/or high-calorie diet than for those with a low-fat and/or calorie intake and more than 2 1/2 times greater in a similar comparison for women.

The National Academy of Sciences has estimated that 60 percent of cancers found in women and 40 percent of cancers found in men are diet-related. Even the more conservative health proponents like the Surgeon General recognize the importance of dietary intervention for cancer prevention.

Fat is the dietary component most often linked to cancer. Diets of patients with colorectal cancer contain significantly more fat and sugars and far less fiber compared to diets of healthy individuals. Intake of dietary fat is also strongly associated with intestinal cancer. Frequent consumption of high fat foods among blacks is directly associated with the incidence of colon cancer.

Fat intake is very high in Finland, where the incidence of coronary heart disease is one of the highest in the world. The incidence of colon cancer, however, is less than one third that of the United States. These lower colon cancer statistics have been attributed to consumption of a popular coarse, whole-grain rye bread. The bread increases fecal bulk to three times that found in most Western nations. The fiber also reduces fecal bile acid concentration, which appears to be one of the culprits in cancer initiation.

Epidemiological studies comparing various dietary components with colon cancer incidence and mortality show a correlation between risk and the high fat, low cereal and low fiber diet typical of Western nations. Cereal fiber apparently has the greatest association with decreased colorectal cancer mortality. Fiber intake in colorectal cancer patients prior to diagnosis was much lower when compared to that of control subjects. Fat intake, on the other hand, was higher in colorectal cancer patients. Study after study shows a marked inverse correlation of colon cancer and cereal consumption. Since studies show a protective benefit of fiber foods, a variety of fiber-rich foods should be eaten to protect against colon cancer.

People with colon cancer were found to ingest significantly more calories in the form of sugar than those without the disease. Fiber-depleted foods, especially sugar, may predispose individuals to the development of colon cancer. In other words, avoid "junk" foods high in fat and sugar and low in dietary fiber.

Omega-3 fatty acids found in fish oils, linseed and flaxseed protect against environmental carcinogens. Omega-6 fatty acids found in evening primrose oil, black currant oil and borage seed oil have similar protective qualities.

Consumptions of tomatoes and strawberries were strongly associated with low cancer risk. A 20-year study found a negative correlation between eating green and yellow vegetables daily and the risk of various cancers. In other words, the higher the consumption of these vegetables, the lower the risk of colon cancer.

Calcium intake is negatively correlated with colon cancer. In one study, families with histories of colon cancer were given 1.25 grams of calcium daily. After two to three months, the number of rapidly proliferating pre-malignant cells in the colon was significantly reduced and were almost equal to those in people at low risk. A similar study demonstrated that approximately two thousand men who had a low intake of calcium and vitamin D were 2.5 times more likely to develop colorectal cancer. Calcium may reduce the adverse effects of bile acids and free ionized fatty acids in the colon.

Magnesium appears to prevent cancer in laboratory animals and epidemiological studies suggest that magnesium levels in soil, water, food and air show an inverse relationship to cancer mortality.

Selenium deficiency is associated with an increased cancer risk. As little as 250-300 micrograms (mcg) per day may help prevent many cancers. The average intake in the United States is approximately 100 mcg per day or less. Most U.S. soil is depleted of this mineral. Cancer incidence is inversely related to selenium forage crop levels. Serum selenium levels are now used to predict the risk of cancer. Adults with serum selenium levels of less than 45 mcg per liter had an excess cancer risk. Cancers of the colon, rectum, prostate, breast and ovary, as well as leukemia, are all inversely related to selenium consumption.

A higher intake of beta carotene has an inverse relationship to cancers of various sites. Vitamin A has been shown to inhibit carcinogenesis.

In surveys of more than 6,000 people, cancer mortality was highest in individuals consuming the lowest amount of vitamin C. Vitamin C may prevent a variety of cancers and environmental carcinogens. Vitamin C prevents the formation of nitrosamine, a potent carcinogen formed from nitrates found in foods and air. A vitamin B6 deficiency may increase the chance of cell mutation from contact with carcinogens, which in turn leads to tumor initiation. Vitamins B12 and C together have been shown to inhibit tumor growth in animals.