Fiber Supplements for IBS and Constipation

Teenager in pain on the toilet
Fiber Supplements for IBS. Peter Dazeley / Getty Images

Fiber supplements, also known as bulk laxatives, are products that relieve constipation. Because they are comprised of fiber, they add heft to and draw water into the stool. This softer, larger stool stimulates the intestines, producing a bowel movement. Fiber supplements are generally available over the counter. Remember that it is very important to drink plenty of fluids when using these products to avoid obstructions within the esophagus or colon.

Here is an overview of the main types:


Psyllium, also known as Isphagula, is a natural (plant-based) form of soluble fiber. Psyllium is sold under a variety of brand names, including:

  • Fiberall
  • Genfiber
  • Konsyl
  • Metamucil

Intestinal bacteria interact with the natural fiber found within psyllium, increasing the risk for symptoms of gas and bloating. In rare cases, an individual may experience a severe allergic reaction to psyllium.

Calcium Polycarbophil

Calcium polycarbophil is a synthetic form of fiber. In contrast to psyllium, calcium polycarbophil runs less of a risk of interacting with gut bacteria and producing unwanted gas. Calcium polycarbophil is found in the following products:

  • Fibercon
  • Equalactin


Citrucel is the only product that contains methylcellulose. Methylcellulose contains both synthetic and natural fiber. It is also resistant to action by intestinal bacteria. Citrucel is a good choice for patients who are following a low-FODMAP diet as it is the only fiber supplement that is non-fermentable.

Do Fiber Supplements Work?

In its 2014 research review, the American College of Gastroenterology concludes that psyllium has good research support for easing constipation and relieving other IBS symptoms. A separate research study compared psyllium and bran as a treatment for IBS. That study found that psyllium was more effective in reducing IBS symptoms and that bran was more likely to cause unwanted side effects.

The Bottom Line

If you are thinking about taking a fiber supplement, psyllium seems to hold the highest promise in terms of effectiveness. Whether you choose psyllium or one of the other types, be sure to drink plenty of water! And don't forget to add more high-fiber foods to your daily diet.


Bijkerk, C., Wit, N., Muris, J., Whorwell, P., Knottnerus, J. & Hoes, A. "Soluble or insoluble fibre in irritable bowel syndrome in primary care? Randomised placebo controlled trial" British Medical Journal 2009 339:b3145.

Ford, A., "American College of Gastroenterology Monograph on the Management of Irritable Bowel Syndrome and Chronic Idiopathic Constipation" American Journal of Gastroenterology 2014 109:S2-S26.

Lembo, A. & Camilleri, M. "Chronic Constipation" The New England Journal of Medicine 2003 349:1360-1368.

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