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Load up on healthy portions of fiber, tomato products, cruciferous vegetables (broccoli, kale, cabbage, Brussels sprouts), garlic, and onions, and eat less meat
Taking 200 mcg a day of this essential trace mineral may offer protection against a variety of cancers
Drink several cups of green tea a day to benefit from the protective polyphenols found in tea leaves
Vitamin C has been shown to improve precancerous conditions in at-risk people
Colon cancer is a malignancy in the colon. It is characterized by unregulated replication of cells creating tumors, with the possibility of some of the cells spreading to other sites (metastasis).
This article includes a discussion of studies that have assessed whether certain vitamins, minerals, herbs, or other dietary ingredients offered in dietary or herbal supplements may be beneficial in connection with the reduction of risk of developing colon cancer.
This information is provided solely to aid consumers in discussing supplements with their healthcare providers. It is not advised, nor is this information intended to advocate, promote, or encourage self prescription of these supplements for cancer risk reduction or treatment. Furthermore, none of this information should be misconstrued to suggest that dietary or herbal supplements can or should be used in place of conventional anticancer approaches or treatments.
It should be noted that certain studies referenced below, indicating the potential usefulness of a particular dietary ingredient or dietary or herbal supplement in connection with the reduction of risk of colon cancer, are preliminary evidence only. Some studies suggest an association between high blood or dietary levels of a particular dietary ingredient with a reduced risk of developing colon cancer. Even if such an association were established, this does not mean that dietary supplements containing large amounts of the dietary ingredient will necessarily have a cancer risk reduction effect.
In Western countries, cancers of the colon and rectum account for more new cancer cases each year than any other site except the lung. Although the genetic susceptibility is low, some families have a predisposition for colon cancer that usually occurs before age 40. Ulcerative colitis and Crohn's disease as well as familial polyposis, are disorders that, to varying degrees, increase the risk of colon cancer.
The initial symptoms of colon cancer depend on the location of the tumor. Cancer in the portion of the colon nearest the left side of the body and areas close to the rectum are the most common cause for a change in bowel habits and consistency of the stool. Cancer in this part of the colon may also cause a colicky pain that is made worse by eating. Blood mixed with the stool and bowel obstruction are other symptoms that characterize cancer at this site. Ineffectual and painful straining at stool may be a sign that the cancer is more advanced. Cancer localized to the part of the colon nearest the right side of the body may cause a generalized abdominal pain and brick red blood. It is commonly associated with iron-deficiency anemia, especially when no other cause can be identified. Cancers closer to the rectum often cause a steady gnawing pain and bright red blood coating the stool.
The following lifestyle changes have been studied in connection with colon cancer.
Most studies show that people who exercise are at lower risk of colon cancer or precancerous changes in the colon, compared with sedentary people.1, 2, 3, 4 Regular exercise appears to be one factor that will predictably lower the risk of colon cancer.
Several studies suggest that obesity in men significantly increases the risk of colon cancer5 or rectal cancer,6 though some scientists believe that obesity may only be a surrogate for other risk factors such as a high-fat diet or lack of exercise.7 Although the relationship between obesity and colon cancer risk in women is less clear, some researchers have found the increased risk of colon cancer in obese women as well as men.8
A history of smoking has been reported to significantly increase the risk of colon cancer in both men9 and women.10 Avoidance of tobacco is an important step in the prevention of colon cancer.
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.
Our proprietary "Star-Rating" system was developed to help you easily understand the amount of scientific support behind each supplement in relation to a specific health condition. While there is no way to predict whether a vitamin, mineral, or herb will successfully treat or prevent associated health conditions, our unique ratings tell you how well these supplements are understood by some in the medical community, and whether studies have found them to be effective for other people.
For over a decade, our team has combed through thousands of research articles published in reputable journals. To help you make educated decisions, and to better understand controversial or confusing supplements, our medical experts have digested the science into these three easy-to-follow ratings. We hope this provides you with a helpful resource to make informed decisions towards your health and well-being.
3 StarsReliable and relatively consistent scientific data showing a substantial health benefit.
2 StarsContradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
1 StarFor an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support.
Green tea and black tea (Camellia sinensis) have both been studied to determine whether they cause or prevent cancer. The evidence on the protective effect of either type of tea is inconsistent.
A number of preliminary studies have shown an association between drinking green tea and a reduced risk of some types of cancer, including colon cancer. In contrast, preliminary studies found that consumers of black tea do not appear to have a reduced risk of any type of cancer.
Selenium has been reported to have diverse anticancer actions. Selenium inhibits cancer in animals. Low soil levels of selenium, probably associated with low dietary intake, have been associated with increased cancer incidence in humans. Blood levels of selenium have been reported to be low in patients with a variety of cancers, including colon cancer. In preliminary reports, people with the lowest blood levels of selenium had between 3.8 and 5.8 times the risk of dying from cancer compared with those who had the highest selenium levels.
The strongest evidence supporting the anticancer effects of selenium supplementation comes from a double-blind trial of 1,312 Americans with a history of skin cancer who were treated with 200 mcg of yeast-based selenium per day or placebo for 4.5 years, then followed for an additional two years. Although no decrease in skin cancers occurred, a dramatic 50% reduction in overall cancer deaths and a 37% reduction in total cancer incidence were observed. A statistically significant 58% decrease in cancers of the colon and rectum was reported.
Caution: Calcium supplements should be avoided by prostate cancer patients.
Through a variety of mechanisms, calcium may have anticancer actions within the colon. Most, but not all, preliminary studies have found associations between taking calcium supplements and a reduced risk of colon cancer or precancerous conditions in the colon. In double-blind trials, calcium supplementation has significantly protected against precancerous changes in the colon in some, but not all, reports. While most evidence examining the ability of calcium supplementation to help prevent colon cancer appears hopeful, no research findings yet support the use of calcium supplements in people already diagnosed with colon cancer.
Preliminary animal and test tube research suggests that CLA might reduce the risk of cancers at several sites, including breast, prostate, colorectal, lung, skin, and stomach. One preliminary study in humans suggests that increasing CLA intake may reduce the risk of colorectal cancer.
People with ulcerative colitis (UC) are at increased risk for colon cancer. Many patients with this disease take the drug sulfasalazine, which depletes folic acid. In a preliminary report, patients with long-standing UC who took folic acid supplements (at least 400 mcg per day) had a 62% lower incidence of colon cancer or precancerous changes in the colon, compared with those who did not supplement with folic acid. Although this difference was not statistically significant, the researchers recommended that people who take sulfasalazine should supplement with folic acid to potentially reduce the risk of colon cancer.
As dietary folate increases, the risks of precancerous polyps in the colon and colon cancer itself decrease, according to some, but not all, reports. In one study, women who had taken folic acid supplements had a statistically significant 75% reduction in the risk of colon cancer, compared with women not taking folic acid supplements, but only when they had been supplementing with folic acid for more than 15 years. In another report, the association between dietary folate and protection from precancerous polyps grew much stronger when use of folic acid supplements was considered (as opposed to studying only folate intake from food). However, one double-blind study found that supplementing with 1 mg of folic acid per day for three to eight years did not prevent recurrences of precancerous polyps in people who had already had at least one polyp.
The protection from colon cancer associated with high intake of folate has been reported to occur more in consumers of alcohol than in nondrinkers. This finding fits well with evidence that folate reverses damage to DNA caused by alcohol consumption. Damaged DNA can lead to abnormal cellular replication—a step toward cancer.
Women, but not men, who took vitamin C supplements were reported to have a reduced risk of colon cancer, according to a preliminary report.
Familial polyposis is a disease that usually leads to colon cancer. In a double-blind study, supplementation with 3 grams per day of vitamin C for nine months led to a reduction in the number of precancerous polyps in people with familial polyposis. In another controlled trial, combining vitamin C with vitamin A and vitamin E led to a dramatic reduction in the recurrence of adenomatous polyps—another precancerous condition of the colon. However, other trials attempting to prevent recurrence of adenomatous polyps using vitamin C alone or in combination with other vitamins have reported no therapeutic effect or only weak trends favoring the group given supplements.
Therefore, the ability of vitamin C supplementation to reduce recurrences of precancerous polyps remains unproven. Whether long-term supplementation with vitamin C would directly help in the prevention of colon cancer has not yet been studied.
Ultraviolet light from sun exposure increases the risk of skin cancers and melanoma. Nonetheless, where sun exposure is low, rates of several cancers have been reported to be high. An association between greater sun exposure and a reduced risk of colon cancer has appeared in some, but not all, studies.
In preliminary reports, people who take vitamin D supplements have been reported to be at low risk for colon cancer, though the differences between supplement takers and others might have been due to chance. More research is needed to determine whether vitamin D supplements may be useful in connection with the prevention of colon cancer.
1. Giovannucci E, Ascherio A, Rimm EB, et al. Physical activity, obesity, and risk for colon caner and adenoma in men. Ann Intern Med 1995;122:327-34.
2. Kono S, Shinichi K, Ikeda N, et al. Physical activity, dietary habits and adenomatous polyps of the sigmoid colon: a study of self-defense officials in Japan. J Clin Epidemiol 1991;44:1255-61.
3. Vena JE, Graham S, Zielezny M, et al. Lifetime occupational exercise and colon cancer. Am J Epidemiol 1985;122:357-65.
4. Martinez ME, Giovannucci E, Spiegelman D, et al. Leisure-time physical activity, body size, and colon cancer in women. Nurses' Health Study Research Group. J Natl Cancer Inst 1997;89:948-55.
5. Murphy TK, Calle E, Rodriguez C, et al. Body mass index and colon cancer mortality in a large prospective study. Am J Epidemiol 2000;152:847-54.
6. Kune GA, Kune S, Watson LF. Body weight and physical activity as predictors of colorectal cancer risk. Nutr Cancer 1990;13:9-17.
7. Shike M. Body weight and colon cancer. Am J Clin Nutr 1996;63(Suppl):442-4S.
8. Ford ES. Body mass index and colon cancer in a national sample of adult US men and women. Am J Epidemiol 1999;150:390-8.
9. Giovannucci E, Rimm EB, Stampfer MJ, et al. A prospective study of cigarette smoking and risk of colorectal adenoma and colorectal cancer in U.S. men. J Natl Cancer Inst 1994;86:183-91.
10. Giovannucci E, Colditz GA, Stampfer MJ, et al. A prospective study of cigarette smoking and risk of colorectal adenoma and colorectal cancer in U.S. women. J Natl Cancer Inst 1994;86:192-9.
Last Review: 06-08-2015
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