Although scientists are not sure what causes colon or rectal cancers, they know that they are associated with lack of exercise, eating too much meat, and the human wart virus (HPV). A study from Sendai, Japan shows that men who spend a lot of time walking are at reduced susceptibility to developing colon cancer (1a).
An extensive review of the world's literature shows that colorectal cancer occurs far more frequently in prosperous industrialized countries, and that dietary factors may cause up to 75 percent of these cancers (1b). You are increased risk for colon cancer if you are overweight, and exercise reduces your risk. Rectal cancer is not affected by obesity or exercise, and may be associated more with infection, such as with the HPV virus that causes genital warts. Since the vast majority of people who are infected with HPV do not get cancer, we have to explain why some do. The leading theory is that of cofactors: some combination of infectious agents, genetic susceptibility or lifestyle factors. I think that rectal cancer requires some kind of infection, but you do not develop the cancer unless you also smoke, lack vitamin D, eat a lot of meat, or some other combination of factors. Colon cancer appears to require some combination of factors such as lack of vitamin D, eating meat, not exercising or not eating enough foods from plants.
David Mangelsdorf, professor of pharmacology at the University of Texas Southwestern in Dallas, reports that Vitamin D may help to prevent colon cancer (1). Colon cancer is associated with eating too much red meat and animal fat, as well as smoking and heavy alcohol use. Your liver removes breakdown products of metabolism from your body and concentrates them into liquid called bile. Then bile passes through a tube leading from the liver to the gall bladder, a balloon that stores the bile. When you eat, the gall bladder contracts and squeezes bile through a tube leading into your intestines, where the bile mixes with the food that you have eaten and breaks down the fat into building blocks called monoglycerides, fatty acids and glycerol that can be absorbed into you bloodstream.
Eating a high-fat diet causes your liver to make more bile, and bile is loaded with a chemical called lithocholic acid, a bile acid that helps digest fat. Lithocholic acid is probably the most toxic compound that your body makes. Lithocholic acid damages the DNA, the genetic material in cells to cause cancer. Giving animals high concentrations of lithocholic acid causes colon cancer, but giving these same animals large doses of vitamin D prevents lithocholic acid from causing colon cancer.
Previous research show that people who develop colon cancer have high concentrations of lithocholic acid in their intestines. This explains why people who have had their gall bladders removed are at increased risk for colon cancer. Your gall bladder is supposed to squeeze bile into your intestines only after you eat. When you have your gall bladder removed, bile flows continuously from your liver into your intestines 24 hours a day. This continuous exposure to bile acids, and lithocholic acids in particular, can cause colon cancer.
So steps to prevent colon cancer include cutting back on meat and animal fat, and making sure that you are not vitamin D deficient. Don't have your gall bladder removed unless it is necessary.
Cancer of the colon as associated with eating lots of refined carbohydrates found in bread and pastas and meat, particularly well-cooked meat and not enough fish, vegetables, whole grains and beans. The omega-3 fatty acids in fish appear to help prevent colon cancer by reducing swelling in your body (2). Whole grains appear to help prevent colon cancer by sweeping foods and carcinogens through the colon at a faster rate. On the other hand, refined carbohydrates in bakery products and pastas are constipating and prolong contact between food and the inner surface of the colon (3). Another theory is that refined carbohydrates cause a high rise in insulin that increases cancer risk. We do not know how different infectious agents affect susceptibility to colon cancer.
Researchers at Harvard show that long-term, cigarette smoking triples your chances of developing colon cancer (3). In the United States, 15 of 16 studies conducted after 1970 in middle-age men and elderly men and, in the 1990s, in women demonstrate an association. Previous studies did not show an association because it takes 30 to 40 years for smoking to cause colon cancer. Cancers require new blood vessels to grow and invade normal tissue. Smoking contains nicotine which is potent angiogenesis factor that causes blood vessels to grow into a tumor to nourish it and cause it to spread.
Three studies which failed to show that fiber prevents colon cancer in North Americans have been widely quoted, but a recent study from South Africa shows that something else in vegetables and grains, called resistant starches, may be the factor that prevents colon cancer (4). Resistant starches cannot be digested in the intestines, so they cannot be absorbed and pass to the colon where bacteria break them down into short chain fatty acids that help prevent cancers, particularly colon cancer. Resistant starches are found in whole grains, beans, nuts and other seeds. Many people avoid the foods that contain resistant starches because they are the most common cause of intestinal gas, which is a byproduct of the bacterial action.
1a) European Journal of Cancer Prevention, October 2007
1b) Alimentary Pharmacology & Therapeutics, Volume 26, 2007
1) May 17, 2002, AAAS' Journal, Science, titled: "Vitamin D Receptor As an Intestinal Bile Acid Sensor" David Mangelsdorf, professor of pharmacology at the University of Texas Southwestern in Dallas
2) EAM deDeckere.Possible beneficial effect of fish and fish n-3 polyunsaturated fatty acids in breast and colorectal cancer.European Journal of Cancer Prevention, 1999, Vol 8, Iss 3, pp 213-221.
3) An updated review of the epidemiological evidence that cigarette smoking increases risk of colorectal cancer. Cancer Epidemiology Biomarkers & Prevention, 2001, Vol 10, Iss 7, pp 725-731. E Giovannucci. E, Brigham & Womens Hosp, Dept Med, Channing Lab, 75 Francis St, Boston,MA 02115 USA
4)R Ahmed, I Segal, H Hassan. Fermentation of dietary starch in humans. American Journal of Gastroenterology, 2000;95(4);1017-1020. Ahmed R, Baragwanath Hosp, Div Gastroenterol, PO Bertsham, ZA-2013 Soweto, SOUTH AFRICA. A high-resistant starch diet and its resultant increase in fermentation products may be partly responsible for protecting the black population against colorectal cancers and other large bowel diseases.
5) MC BoutronRuault, P Senesse, J Faivre, N Chatelain, C Belghiti, S Meance. Foods as risk factors for colorectal cancer: a case-control study in Burgundy (France).European Journal of Cancer Prevention, 1999, Vol 8, Iss 3, pp 229-235.
6) H Horie, K Kanazawa, M Okada, S Narushima, K Itoh, A Terada.Effects of intestinal bacteria on the development of colonic neoplasm: an experimental study.European Journal of Cancer Prevention, 1999, Vol 8, Iss 3, pp 237-245.
7)R Sinha, WH Chow, M Kulldorff, J Denobile, J Butler, M GarciaClosas, R Weil, RN Hoover, N Rothman.
8) Trans-Fatty Acids and Colon Cancer. Martha L. Slattery, Joan Benson, Khe-Ni Ma, Donna Schaffer, and John D. Potter. Nutrition and Cancer 39(2):170-175, 2001.
ASPIRIN TO PREVENT COLON CANCER: If you have polyps in your colon or a strong family history of colon cancer, your doctor may prescribe one adult aspirin every other day. At least 11 studies show that aspirin and two studies show that estrogen help to prevent colon cancer. Aspirin blocks certain prostaglandins, and some metabolites of prostaglandins are known to cause and spread cancer. Colon cancer cells make more prostaglandins than surrounding tissue and blocking certain prostaglandins prevents colon cancer. Estrogen helps to clear bile salts which are known to cause cancer. Colon cancer is highly curable when it is diagnosed before it has spread, and the cure rate drops below 40% when it is diagnosed after it has spread. Therefore, people over the age of 50 should have a colonoscopy or barium enema X-ray at least once to check their colons for polyps, premalignant growths on the inner lining of the colon. If they have no polyps, no family history of colon cancer and no colon symptoms, many doctors feel that they don't need to be checked more often than once every ten years. However, if they have polyps, the doctor should remove them and they should be told that they are at increased risk for colon cancer. To help prevent colon cancer eat large amounts of fiber-rich foods including fruits, vegetables, whole grains and beans and avoid being overweight and eating too much food, particularly fatty foods, and drinking alcohol
1)Koutsos, Markos et al. Can nonsteroidal anti-inflammatory drugs be recommended to prevent colon cancer in high risk elderly patients? Drugs and Aging. 1995;6(6):421-425.
2) Marnett LJ. Aspirin and related nonsteroidal anti-inflammatory drugs as chemopreventive agents against colon cancer. Preventive Medicine 1995;24:103-106.
3)Karnes WE. Current Opinion in Gastroenterology. 1994(Jan);10(1):19-26.
4) ML Slattery, TD Berry, J Potter, B Caan. Diet diversity, diet composition, and risk of colon cancer (United States). Cancer Causes & Control 8: 6 (NOV 1997):872-882. Women who consumed the largest percentage (pi their food items in the form of plant foods (fruits, vegetables, or whole grains) were at a reduced risk of developing colon cancer.
5) E Destefani, M Mendilaharsu, H Deneopellegrini, A Ronco Influence of dietary levels of fat, cholesterol, and calcium on colorectal cancer. Nutrition and Cancer - an International Journal 29: 1(1997):83-89.calcium effect was maximal at low levels of dietary fat (and cholesterol intake), whereas fat (and cholesterol intake) showed a positive monotonic increase in risk of colorectal cancer at high levels of calcium intake.
6) E Fernandez, C Lavecchia, C Braga, R Talamini, E Negri, F Parazzini, S Franceschi. Hormone replacement therapy and risk of colon and rectal cancer. Cancer Epidemiology Biomarkers & Prevention 7: 4(APR 1998):329-333.
7) Chen MJ et al. Recent use of hormone replacement therapy and the prevalence of colorectal adenomas. Cancer Epidem Biomarker Prev 1998 MAR;7(3):227-230. 7) MJ Hill. Cereals, cereal fibre and colorectal cancer risk: a review of the epidemiological literature. European Journal of Cancer Prevention 7: Suppl. 2(MAY 1998):S5-S10.
8) C Lavecchia, L Chatenoud. Fibres, whole-grain foods and breast and other cancers. European Journal of Cancer Prevention 7: Suppl. 2(MAY 1998):S25-S28.
9) J Faivre, A Giacosa. Primary prevention of colorectal cancer through fibre supplementation. European Journal of Cancer Prevention 7: Suppl. 2(MAY 1998):S29-S32.
10) D Kritchevsky. Cereal fibres and colorectal cancer: a search for mechanisms. European Journal of Cancer Prevention 7: Suppl. 2(MAY 1998):S33-S39.
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