Dear Dietitian: functional fiber
I am health conscious and try to get enough fiber in my diet, but sometimes I miss the mark. I noticed some protein bars have 10 grams of fiber. Are these good for you?
The Dietary Guidelines recommend Americans consume 25 to 30 grams of fiber per day. Fiber is found naturally in plant foods and is defined as an indigestible carbohydrate. This simply means the human body cannot break down fiber, and it passes through the digestive system unchanged. There are two main types of fiber--soluble and insoluble. Soluble fiber is found in oats, apples, nuts, flaxseeds, and beans, to name a few. Insoluble fiber is found in wheat bran, barley, broccoli, dark green leafy vegetables, and root vegetable skins.
Most Americans fall dismally short of reaching the recommended dietary fiber intake, with an average consumption of about 15 grams per day. Food manufacturers have started adding fiber to products such as yogurt, protein bars, beverages, and cookies. To distinguish this type from naturally-occurring fibers, they are referred to as added fiber, functional, synthetic, or isolated fiber. They can be extracted from foods that naturally contain fiber or produced in a lab.
Health benefits of a high fiber diet include less risk of being overweight, reduced incidences of type 2 diabetes, heart disease, and some types of cancer. Do added fibers carry the same health benefits as natural fibers?
In order to protect consumers, the FDA proposed a regulatory definition of dietary fiber. It required food manufacturers to present scientific evidence on the health benefits of added fibers. They must have at least one of the following physiological benefits: lowers blood glucose, lowers cholesterol levels, lowers blood pressure, increases the frequency of bowel movements, increases mineral absorption in the intestinal tract, or reduces caloric intake (1).
The added fibers that passed the health test are: beta-glucan soluble fiber, psyllium husk, cellulose, guar gum, pectin, locust bean gum, hydroxypropyl methylcellulose, glucomannan, and cross-linked phosphorylated RS4. The FDA plans to add the following substances to the list of acceptable functional fibers: mixed plant cell wall fibers, arabinoxylan, alginate, inulin (chicory root), high amylose starch, galactooligosaccharide, polydextrose, resistant maltodextrin/dextrin (2). These ingredients must be listed on the nutrition label.
It may come as no surprise that a dietitian recommends getting most of your fiber in whole foods for two reasons. First, the research on fiber and disease prevention has been conducted on whole foods like fruits, vegetables and whole grains. Fiber isn't isolated in the research process. And second is what I like to call the x factor, which could be something research has not yet uncovered. For example, it could be a certain nutrient plus fiber that together have a protective benefit. That said, supplementing your fiber intake with some functional fiber is a fine strategy.
Until next time, be healthy!
1-2. Questions and answers on dietary fiber (January 10, 2020) Retrieved from https://www.fda.gov/food/food-labeling-nutrition/questions-and-answers-dietary-fiber
Leanne McCrate, RDN, LD, CNSC, is an award-winning dietitian nutritionist based in Missouri. Her mission is to educate consumers on sound, scientifically-based nutrition. Do you have a nutrition question? Email her at firstname.lastname@example.org. Dear Dietitian does not endorse any products, health programs, or diet plans.