Colon and Rectal Cancers - Dietary Factors

Currently it is reasonable to reduce saturated fats and transfatty acids and to favor monounsaturated oils and polyunsaturated oils, particularly containing omega-3 fatty acids.

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Meat and High-Temperature Cooking

Some evidence suggests that red meat raises the risk for colon cancer. Red meat contains dietary iron, which has been associated with a higher risk for colon cancer. In fact, early results in 2000 from the largest study on diet and cancer to date have supported previous studies linking red meat with intestinal tumors.

High-temperature cooking (grilling, broiling, or pan-frying) has been specifically associated with increased risk for colon polyps and colon cancer. Over-cooking meat increases the amount of carcinogens called heterocyclic amines, which has been associated with cancerous changes.

Some research has been focusing on acrylamide, a chemical found in high amounts in certain foods cooked at high temperatures, especially fried potatoes, and also bread products. Animal studies have suggested that acrylamide is a carcinogen. A surprising 2003 study, however, found no evidence of risk for colorectal or other cancers with high intake of foods that contain large amounts of this chemical.

Dairy Products and Calcium

Milk, Lactose, and Probiotics. In a Finish 2001 population study, adults who drank the most milk had the lowest risk for colon cancer. A 2004 study published in the Journal of the National Cancer Institute supports this conclusion. In this review of 10 epidemiologic studies that included more than half a million people, people who consumed more milk and calcium had a lower risk of developing colorectal cancer. Milk not only contains calcium but also other compounds, such as lactose, that may help protect against colon cancer. Yogurt specifically has been associated with a lower risk for colon cancer if it contains live active bacterial cultures, such as Lactobacillus acidophilus, that are called probiotics. These "friendly bacteria" appear to protect the colon from cancerous changes. (Acidophilus and other probiotic capsules are also available in health food stores.) Results are mixed on other fermented milk products, such as buttermilk and cheese, which in one study were associated with a higher risk. The reasons for this were not clear.

Calcium. Calcium, which is found in dairy products, is also associated with colon cancer protection. Most studies show a possible protective effect from either high-calcium diets or calcium supplements. The protective effect has been observed as early as one year after calcium supplementation began. A large 2002 study concluded that daily intake of about 700 mg, from food or supplements, reduces the risk of colon cancer, but intake beyond this level does not add any further protection. Calcium supplements may even offset certain effects of dietary iron, found in red meat and other foods, which may increase the risk for colon cancer. More work in this area is needed, however.