Fiber Supplements 101: Psyllium, Inulin, and More

Written By: Owennie Lee, RD

Title: Registered Dietitian

Alumni: University of British Columbia

Last Updated on:

With the recommended intake of fiber between 25 and 38 grams per day, some of us may feel we have to resort to fiber supplements to help come close to the target and ease gut issues such as constipation and bloating. Before shelling out money, check out the major differences of 4 common fiber supplements (such as psyllium and inulin) available in the market.

Fiber Supplements 101

A survey of the most popular fiber supplements in the marketplace reveals that they are almost always made up of a single type of soluble fiber. One serving of these supplements typically provides 3-6 grams of fiber. Most soluble fibers can help alleviate constipation by holding on to water in the digestive tract, making stools softer and easier to pass. Certain types of soluble fiber that are viscous (e.g., beta-glucan, pectin, and psyllium) have also been proven to help lower blood cholesterol. Insoluble fibers, although they can help with constipation, are almost never found in fiber supplements because they don’t dissolve in water, making them difficult to take.

Common Types of Fiber in Supplements

1. Psyllium

  • Common Brand: Metamucil
  • How Much Fiber
    • 5 g per 2 tsp (Premium)
    • 6 g per 2 tsp (4-in-1)

Psyllium is a viscous, soluble fiber that is the most common fiber source in supplements. Psyllium’s cholesterol-lowering ability has earned the FDA’s approval, allowing foods containing psyllium to make a health claim about reducing risk of heart disease. However, a major disadvantage of psyllium is that it thickens rather quickly and may not be as easy to incorporate into beverages. Psyllium is also fermented by bacteria in the colon and may cause bloating and flatulence in some individuals.

2. Inulin

  • Common Brand: Fiber Choice Prebiotic Fiber Chewable
  • How Much Fiber
    • 4 g per 2 chewable tablets (Fiber Choice)

Inulin is a non-viscous, soluble fiber that is also known as a prebiotic. It is extracted from foods such as chicory root. Aside from fiber supplements, inulin is also being added to myriad food products, such as yogurt and bread, to boost fiber content. Inulin is tasteless, colorless, odorless, and textureless, making it extremely easy to incorporate into foods and beverages. However, inulin is not effective in reducing cholesterol. In addition, inulin seems to be more prone to cause gas and bloating. The fermentation of inulin produces more hydrogen and total gas than psyllium and wheat dextrin, according to a study published in January 2010 by a group of University of Minnesota researchers.

3. Wheat Dextrin

  • Common Brand: Benefiber Prebiotic Fiber Powder
  • How Much Fiber
    • 3 g per 2 tsp

Wheat dextrin is another type of non-viscous, soluble fiber that is considered a bulk-forming laxative. Since it is non-viscous, it does not form a gel in the digestive tract that binds with cholesterol, rendering it ineffective in lowering blood cholesterol. It is fermented in the colon to produce gas.

4. Methycellulose

  • Common Brand: Citrucel
  • How Much Fiber
    • 4 g per 2 tsp (Powder)
    • 1 g per 2 caplets (Caplets)

Methylcellulose is a viscous, soluble fiber that is a derivative of cellulose. Its manufacturers claim that because it is not fermented in the colon. Therefore it is less prone to cause bloating and gas.

Natural Fiber from Food vs. Fiber Supplements

Isolated fibers, such as the above fiber supplements, don’t perform the same as natural fiber from food. With food, not only do you get a combination of insoluble and soluble fibers, you also get all the other nutrients that foods have to offer. Some high fiber foods that combine great nutrition include lentils (1/2 cup delivers 7.8 grams of fiber) and oat bran cereal (5.7 grams per 1/2 cup). In addition, the old-fashioned prune has actually been proven to be more effective than psyllium in treating mild to moderate constipation, according to a study published in April 2011 by a group of researchers from the University of Iowa Carver College of Medicine.

The Bottom Line

Including more high-fiber foods in your diet is certainly the way to go if you want to hit the recommended fiber intake. If you decide to take fiber supplements, select the type that provides the benefits that you are after. Different products under the same brand name may contain different sources of fiber, so be sure to check the ingredients list. With all fiber supplements, start slowly to let your body adjust, and drink plenty of water because otherwise they can cause blockage of your digestive tract.

Nutrition 101

fiber, fiber supplements, inulin, metamucil, prebiotic, psyllium


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