Colon Cancer Prevention (Holistic)

Cabbage, Brussels sprouts, broccoli, and cauliflower belong to the Brassica family of vegetables, also known as “cruciferous” vegetables. In test-tube and animal studies, these foods have been associated with anticancer activity, possibly due to several substances found in these foods, such as indole-3-carbinol, glucaric acid (calcium D-glucarate), and sulforaphane. In a preliminary human study, people who eat cruciferous vegetables were reported to have lower-than-average risks for colon cancer.

“Secondary bile acids” are substances in the gut that may increase the risk of colon and rectal cancers. Some researchers have hypothesized that coffee drinking might reduce the risks of colon and rectal cancers by decreasing the intestinal level of these substances. An analysis of preliminary studies suggests coffee drinkers have a significantly lower risk of these cancers compared to the risk in people who do not drink coffee. However, only studies using the weakest methods of inquiry have found this protective effect. Due to the lack of support from studies using stronger methodology, the association between coffee drinking and protection against colon or rectal cancers remains unproven.

Until recently, most studies reported that people who ate a high-fiber diet were found to be at low risk for colon cancer. Some researchers believed protection against colon cancer comes specifically from eating wheat bran as opposed to other fibers. A clear understanding of how fiber might protect against colon cancer risk remains somewhat elusive.

Recent research has begun to cast doubt on whether fiber provides significant protection against colon cancer, suggesting instead that consumption of meat and other animal products may be the primary culprit. Despite these recent reports, however, some doctors continue to believe that, until more definitive information is available, people wishing to reduce their risk of colon cancer should consume more fiber in their diets.

Consuming a diet high in insoluble fiber is best achieved by switching from white rice to brown rice and from bakery goods made with white flour or mixed flours to 100%-whole-wheat bread, whole-rye crackers, and whole-grain pancake mixes. Refined white flour is generally listed on food packaging labels as “flour,”“enriched flour,”“unbleached flour,”“durum wheat,”“semolina,” or “white flour.” Breads containing only whole wheat are often labeled “100% whole wheat.”

Garlic (Allium sativum) and onion (Allium cepa) belong to the group of plants known as Allium. Many other edible plants are found in this group, including leeks and chives. Preliminary studies have investigated the association between eating Allium herbs and the incidence of cancer. The most consistent data come from research focusing on the protective effects of Allium consumption against cancers of the gastrointestinal tract. Several preliminary studies have found that people who consume more Allium vegetables appear to have a reduced risk of colon cancer and precancerous colon polyps.

Constituents in garlic and onions prevent the conversion of nitrates (compounds found in vegetables and, to a lesser extent, in water) to cancer-causing nitrites and nitrosamines.

Preliminary studies have reported associations between an increasing intake of sugar or sugar-containing foods and an increased risk colon cancer. Whether this association exists because sugar directly promotes cancer, or because sugar consumption is only a marker for some other dietary or lifestyle factor, remains unknown.

Tomatoes contain lycopene—an antioxidant similar in structure to beta-carotene. Most lycopene in our diet comes from tomatoes, though traces of lycopene exist in other foods. Lycopene inhibits the proliferation of cancer cells in test-tube research.

A review of published research found that higher intake of tomatoes or higher blood levels of lycopene correlated with protection from cancer in 57 of 72 studies. Findings in 35 of these studies were statistically significant. Evidence of a protective effect for tomato consumption was strongest for a variety of other cancers, but some evidence of a protective effect also appeared for colon cancer. Many doctors recommend that people who are not allergic to tomatoes increase their intake to reduce their risk of cancer.

Associations between salt intake and colon and rectal cancers are reported in some, but not all, preliminary studies. Doctors often do not mention salt restriction as part of a cancer-prevention diet because the only malignancy strongly associated with salt—stomach cancer—is no longer common in the United States despite our high intake of salt.

Most, but not all, studies show meat eaters have a high risk of colon cancer. In some colon cancer studies, the association has been limited to consumption of sausage or other processed meats.

The association between cancer and consumption of meat depends in part on how well the meat is cooked. Well-done meat contains more carcinogenic material than does lightly cooked meat. Recent evidence from preliminary studies shows that people who eat well-done, fried or heavily-browned meat have a high risk of colon cancer.

However, not every report has found that exposure to carcinogens found in well-done meat leads to an increased risk of colon cancer. Some studies may have failed to find this link because they did not consider the effect of genetics. Susceptibility to the colon cancer-causing effects of well-cooked meat appears to be genetically determined. Therefore, only some people appear to increase their risk of colon cancer by consuming well-cooked meat. However, people are rarely tested to see if they are “rapid acetylators”—meat-eaters considered to be at high risk of colon cancer—except as subjects in a research experiment.

Most nutritionally oriented doctors tell people wishing to reduce their risk of colon cancers to stop eating meat, or at least significantly reduce consumption, and to limit intake to meat that is rare or medium-cooked. Removing all meat from the diet may be safest because consumption of even rare or medium-cooked meat has been associated with at least some increase in risk.

Dietary fat intake has long been regarded as an important nutritional influence on colon cancer development. Nevertheless, the association between colon cancer and total dietary fat remains inconsistent. Although there are known mechanisms by which a high dietary fat intake could promote tumor growth in the colon, a review of the research shows the strongest dietary association with colon cancer to be the intake of meat, not necessarily the fat content of the meat.

Most, but not all, preliminary reports have found an association between beer drinking (though not consumption of other forms of alcohol) and rectal cancer. Beer drinking has also been associated with an increased risk of precancerous changes in the colon. Nitrosamines––cancer-causing chemicals found in beer––may be partially responsible for these associations. Several studies have found consumption of any form of alcohol to be associated with an increased risk of rectal and colon cancers, the link between rectal cancer and beer being only slightly stronger than the association between rectal cancer and consumption of other forms of alcohol.

Alcohol can indirectly damage DNA—the material that allows cells to replicate normally. Abnormal replication of cells can lead to cancer. Folic acid, a B vitamin, appears to protect against alcohol-induced DNA damage. Increasingly, researchers believe that folic acid may be able to protect against some of the colon cancer-causing effects of alcohol. Doctors recommend that people wishing to reduce their risks of colon and rectal cancers abstain from drinking alcohol.

Those who continue to drink should take folic acid supplements. In one report, women taking multivitamins (often containing 400 mcg of folic acid per day) for at least 15 years had a 75% lower risk of colon cancer compared with women not taking such supplements.