Colon cancer remains the 2nd leading cancer killer in this country, despite the tremendous progress we have made through colon cancer screening (primarily colonoscopy). Many factors can lead to colon cancer, including genetics (such as a family history of colon cancer), age, obesity, tobacco use, and underlying inflammatory bowel disease. Diet likely plays a role as well. Many patients ask us what diet changes they can make to reduce their risk of colon cancer. Let’s review a few potential dietary factors. Keep in mind that it is very difficult to study the role of diet in cancer and very few randomized, controlled studies have been conducted. Most of the information below is observational, meaning that people with and without cancer are asked about their diets, and comparisons are made.

Red meat:

Long-term consumption of red meat and processed meats appears to increase the risk of colon cancer. This is supported by multiple studies. It is estimated that the risk of cancer increases by 20% for every 100g/day increase in red meat (about 3 ounces). It has been hypothesized that barbecuing and other high-temperature cooking is of particular risk.

Level of evidence: Convincing.

Fiber:

Fiber is hypothesized to reduce the risk of colon cancer by bulking stool, decreasing time spent in the bowels, diluting potential cancer-causing contents, and reducing fat. Cereal fibers (such as whole grains) may be of the greatest benefit. It is estimated that every 10g increase in fiber each day reduces the risk of colon cancer by 10%.

Level of evidence: Convincing

Calcium and dairy products:

Calcium is an essential nutrient for bone health and may have anti-tumor properties. Multiple studies have shown that calcium intake is associated with the risk of colon polyps and colon cancer, though the evidence is somewhat mixed. In fact, a study released last week did not show a benefit. Still, there does appear to be an increase in colon cancer risk among people who consume less than 700-1000mg/day of calcium, so it is reasonable to ensure a healthy intake.

Level of evidence: Probable

Vitamin D:

Low vitamin D levels have been associated with many cancers, including colon cancer, though the link is not certain. Vitamin D does have proposed anti-cancer properties, but a benefit has not been shown in randomized, controlled studies. There are other benefits of maintaining an adequate vitamin D level (primarily bone health), therefore it reasonable to maintain sufficient intake.

Level of evidence: Limited-suggestive

Fat:

Countries with higher per-capita consumption of red meat and animal fats have higher rates of colon cancer. This lead to a hypothesis that fats might be responsible. However, there is no clear evidence that dietary fat is a specific factor.

Level of evidence: Limited-no conclusion

Fish consumption:

Eating more omega-3 fatty acids (such as fish and fish oil) is associated with a lower risk of colon cancer in observation studies, though randomized controlled studies have not been conducted.

Level of evidence: Limited-no conclusion

Bottom line:

There are multiple factors that contribute to one’s risk of colon cancer, including diet. However, the most important way to prevent colon cancer is to make sure you are up to date with colon cancer screening. Reducing red meat consumption and increasing fiber may help, but will not eliminate risk entirely.

Christopher McGowan, MD, MSCR