Dear Dietitian,

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?

Jim

Dear Jim,

The Dietary Guidelines recommend Americans consume 25 to 30 grams of fiber per day. Fiber is defined as an indigestible carbohydrate, which means the human body cannot break it down, and it passes through the digestive system unchanged. Fiber is found naturally in plant foods and exists in two forms, 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.

Health benefits of a high fiber diet include rates of obesity, type 2 diabetes, heart disease, and some types of cancer. 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 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. 

To protect consumers, the Food and Drug Administration (FDA) proposed a regulatory definition of dietary fiber. It requires 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).

Some of the added fibers that met the FDA requirements are: beta-glucan soluble fiber, psyllium husk, cellulose, guar gum, pectin, locust bean gum. Based on a scientific review, the FDA may add the following substances to the list of acceptable functional fibers: mixed plant cell wall fibers, inulin (chicory root), high amylose starch, polydextrose, resistant maltodextrin/dextrin, and others (2). These ingredients must be listed on the nutrition label.

It may come as no surprise that Dear 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. 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 particular nutrient plus fiber that has a protective benefit. That said, supplementing your fiber intake with some functional fiber is a fine strategy.

Until next time, be healthy!

Dear Dietitian

References

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