Colon Cancer

Colon cancer prevention
on a dinner plate

Colon cancer is the second most common cause of death from cancer for men and women in the United States. But colorectal cancer prevention does not generate a lot of talk or publicity, even though it is exceeded only by lung cancer, and more women die from colon cancer than from breast cancer. If the lack of discussion about prevention is because people believe they have to move to complete vegetarianism in order to reduce risk, I can clear that up right now: a healthy diet is really, really important for colorectal cancer prevention, but strict vegetarianism is not necessary.

First, some general principles. In holistic medicine, we like to address health promotion from a natural lifestyle and healthy diet first. For colon cancer prevention, your best bets are to maintain regular physical activity, restrict your intake of red and processed meats, eat more vegetables and fruits, keep body weight low to normal throughout life, and avoid excess alcohol (that is, no more than one drink per day for women, or two drinks per day for men). There are also some specific vegetables with good research showing their cancer prevention value, and I will give them some extra time and space here.

The American Institute for Cancer Research updated its review of physical activity, nutrition and cancer prevention in early 2008. The conclusion: regular physical activity protects against several types of cancer, specifically including colorectal cancer. They noted that this reduction in risk is accounted for by the physical activity itself and not simply as a function of lower weight. To be clear: increased physical activity reduces risk of cancer regardless of body weight. But since we know that obesity is itself also an independent risk factor for cancer, and that higher levels of physical activity are associated with less obesity, it also follows that regular physical activity reduces risk of cancers by the pathway of weight reduction.

Eating less red meat and less processed meat is important for several reasons: one is simply that we know from large population based epidemiologic studies that people who eat red meat more often are at higher risk of developing colon cancer. And meats which are charred on a grill or cooked “well done” are likely to contain cancer-causing heterocyclic amines and polycyclic aromatic hydrocarbons. Another has to do with the chemical carcinogens generated when we eat processed meats with preservatives. The addition of nitrates or nitrites to meats as a preservative (such as in processed deli meats) can lead to cancer, because these form N-nitroso compounds (some of which are known carcinogens) in the meat or in the individual consuming the preservative-rich meat. My advice on meats: eat less, and when you do eat it, avoid meat with preservatives such as nitrates, and enjoy your steak cooked medium at most.

Alcohol, despite its potential benefits for heart health when intake is moderate (maximum one drink per day for women, two drink maximum for men), is clearly a cancer promoter. I never encourage anyone who does not already drink to begin for any reason (heart or otherwise), and if you have a strong family history of cancer, I would especially discourage it. A healthy diet, rich in a large variety of vegetables and fruits (preferably 9 servings per day), is overall your best risk reduction strategy for colon cancer. So while I cannot emphasize strongly enough the value of daily variety and a rainbow of vegetable and fruit colors on your plate, there are several specific ones which have research data highlighting their importance for colorectal cancer prevention.

You won’t have to be near me for long to hear about the health benefits of garlic. Garlic’s botanical name is allium sativum. The family of allium vegetables, including especially garlic and onions, were discovered early in human history, and in many cultures around the world, to have medicinal value. Now after centuries of observation around the world, we have modern research showing that long term regular ingestion of garlic as a food has value in preventing both stomach and colorectal cancer.

There is ongoing debate in the medical literature over the exact components of garlic which are responsible for the benefits, and whether cooked or raw is better. I encourage you to eat some garlic every day, however you can, a single clove per day would be a good goal, and consider a tablet form supplement on other days. But my preference is to enjoy it as food, and continue to discover new ways to let it add spice and interest to my dinners!

Moving from garlic to its close relative onions (allium cepa), there is more good news for cancer prevention. A very large population based study from southern Europe, published in 2006 in the American Journal of Clinical Nutrition, showed that onions have a protective effect against cancer of the colon/rectum. So if you are already a fan of onions several times weekly, feel good about your eating, and continue to expand your variety beyond that. If you do not regularly eat onions, experiment with different ways of cooking and preparing until you find enough ways to enjoy some onions at least twice weekly.

As a group, people who eat higher quantities of whole grains have a decreased risk of cancer. This is largely due to the amount of fiber ingested, and the best data suggest that an amount well beyond the standard American diet is necessary for colorectal cancer prevention, at least 30 grams per day. The best type of fiber is still being debated, but we know that soluble fiber aids the health of colon lining cells and helps them resist changes leading to cancer. One specific soluble fiber with colon cancer prevention action is inulin. Inulin functions in the intestine as a prebiotic, meaning it is a food for the “good” bacteria that keep your colon healthy and balance your immunity. A study from British Journal of Nutrition in 2005 summarized very positive animal and human data on the role of inulin in preventing colon cancer. Inulin is found naturally in garlic, onion, artichoke, asparagus, and jicama. It has also become a popular functional food additive recently, and is isolated from chicory root to be added to foods such as yogurts.

So in summary, for colon cancer prevention, stay physically active at a level appropriate for your age, limit consumption of red and processed meats, eat more vegetables and fruits, maintain healthy body weight, and avoid excess alcohol. I believe those steps are simple and achievable, and certainly leave plenty of room for an interesting diet and enjoyable life!


To your health and wellness,



Robert Pendergrast, M.D.




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