A. Nicola McKeown, PhD, an associate professor at the Friedman School and a scientist at the HNRCA renowned for her research on whole grains and health, answers: “Constipation is a common problem that affects 16 percent of the U.S. population (and about a third of adults age 60 and older). Health professionals recommend patients suffering from constipation increase their intake of dietary fiber. Eating a variety of plant foods is one sure way to increase fiber and minimize your risk of constipation.
“Different types of fiber have different properties and thus promote health in different ways. Poorly fermentable insoluble fibers, like those in bran, are not broken down by our gut microbes, and the large, coarse particles irritate the lining of the large bowel, stimulating the release of water in the bowel. This softens and adds bulk to the stool, helping it to pass more easily. The fiber found in oatmeal (beta-glucan) is a soluble, viscous fiber that forms a gel when mixed with water, but beta-glucan is fermentable (i.e. broken down by our gut microbes). As the fiber is broken down in the colon, it loses the water-holding properties that help reduce constipation, so oatmeal is not a good choice for promoting regularity.”