For Better Digestive Health, Choose Your Fats Carefully

A recent study suggesting trans fats increase colorectal cancer risk supports the notion that substituting more healthful fats in the diet is the best path to good health.

Though some trans fats occur naturally, they are most often the result of oils that have undergone partial hydrogenation, a food processing technique that lengthens a food’s shelf life. Trans fats are commonly found in items such as margarine, chips, crackers, cookies, donuts, pastries, and other convenience foods.

More trans fats, less healthy gut

In the new study, published in the American Journal of Epidemiology, 622 people who underwent a routine screening colonoscopy were interviewed about dietary and other factors thought to be related to colorectal cancer. Researchers used this information to estimate how much trans fat each person regularly consumed and compared these numbers to the colonoscopy results.

Compared with those who ate the least trans fats, people who ate the most had an 86% higher likelihood of having colorectal adenomas—small growths, or polyps, in the colon and rectum that, if left untreated, can develop into colorectal cancer. This finding adds to the accumulating evidence that trans fats are just plain bad for us.

Walter Willett, MD, PhD, a professor of epidemiology and nutrition at Harvard Medical School and one of the nation’s foremost experts on food and health advocates a move away from these unhealthy fats. Regarding the health of the American diet, he said, “The worst single specific problem is trans fats.” And based on results of an earlier study, Dr. Willett concluded that trans fats represent “the biggest food processing disaster in US history.”

Simple steps towards better health

Your body’s cells need some fats to function, but as this study confirms, the type you consume makes all the difference. The good news is that avoiding trans fats is as simple as focusing on simple food.

• Emphasize whole foods. The closer a food is to its natural form, or what it looks like when it comes out of the ground or off the tree or vine, the less likely it is to contain harmful fats. Avoid foods that contain the words “partially hydrogenated” in the ingredient list. Trans fat intake should not exceed 1 percent of total calories each day. For a 2,000 calorie diet, this means eating no more than 2.2 grams of trans fat per day.

• Remember that healthier fats, specifically the mono- and polyunsaturated types, are often liquid at room temperature. By comparison, the less healthy trans and saturated fats are typically solid at room temperature. To get more good fats in your diet, cook with oils, such as olive oil, and choose foods such as nuts, avocados, and fatty fish over well-done red meats.

• Match your fat intake to your overall health goals. People at risk for obesity, heart disease, diabetes, and cancer should consume no more than 30% total calories from fat. For a 2,000 calorie diet, this means eating no more than 67 grams of total fat per day.

In general, the same principles that support heart health support the health of your gut as well. Stick to unprocessed items such as vegetables, fruit, nuts and seeds, whole grains, and beans (legumes) and you won’t have to give trans fats a second thought.

(Am J Epidemiol 2008;168:289–97; Am J Clin Nutr 1997;66:1006S–1010S)

Suzanne Dixon, MPH, MS, RD

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