It is recommended that adults consume between 25 and 30 grams of dietary fiber a day. The average American currently gets about half that amount. According to the latest Dietary Guidelines for Americans, dietary fiber is a “nutrient of public health concern,” meaning this low level of intake could actually be detrimental to our health. So, it’s potentially good news that food manufacturers are adding fiber to processed foods. But is that fiber as good for our health as fiber found naturally in fruits, vegetables, nuts, legumes, and whole grains?
Health Benefits of Fiber. According to a research review co-authored by Nicola McKeown, PhD, a scientist with Tufts’ Nutritional Epidemiology program and an associate professor at the Friedman School, there is reproducible evidence that dietary fiber found naturally in foods has a role in lowering cholesterol, improving glycemic control, and preventing constipation. And fiber may have more health benefits as well. “Research in this field is continually expanding,” says McKeown. “We’ve only begun to consider things like how the gut microbiota utilize different types of dietary fibers to potentially impact health.” Continue reading
Nicola McKeown, PhD, associate professor at the Friedman School, answers: “Beans (and other foods high in viscous soluble fiber, such as apples and barley) can be helpful for lowering blood cholesterol levels. This type of fiber thickens and forms a gel-like substance in the digestive tract. The gel traps bile acids which are needed for the digestion and absorption of fats and fat-soluble vitamins in the small intestine. The trapped bile acids are eliminated from our bodies via our feces. Once bile acids are excreted, this signals our liver to make more bile acids, which requires cholesterol, thus leaving less circulating cholesterol available to be incorporated into unhealthy low-density lipoproteins (LDL cholesterol).
“In addition to beans, many plant foods are good sources of soluble fibers, including apples, pears, plums, and citrus fruits, oats and oat-based products, barley, shitake mushrooms, and seaweed. Another viscous soluble fiber, psyllium is added to various foods such as ready-to-eat cereals and is also available in concentrated form as an isolated fiber in over-the-counter products such as Metamucil (which should only be taken under the direction of your physician). A diet rich in a variety of beans, nuts, seeds, fruits, vegetables, and whole grains will deliver a wide array of cholesterol-lowering soluble fibers.”