Study Determines Which Type of Fiber Is Best for Constipation

psyllium in dish on table

Luis Echeverri Urrea / Getty Images

Key Takeaways

  • Using a fiber supplement daily can help treat chronic constipation, according to a review and meta-analysis of 16 clinical trials.
  • The optimal dose of fiber supplement is more than 10 grams per day, with psyllium and pectin supplements being more effective than other types of fiber.
  • If you’re going to add fiber to your diet, do it gradually. This will help you avoid side effects like excessive flatulence or bloating.

Occasional constipation can leave you feeling blocked up, bloated, and dreading the eventual painful bowel movement. Chronic constipation, on the other hand, means that’s an ongoing or recurring problem.

So what can you do about chronic constipation? New research is dedicated to finding solutions.

A July review and meta-analysis of 16 randomized control trials found that using fiber supplements for at least four weeks had a significant effect on the frequency of bowel movements and improved their consistency. The studies involved 1,251 patients who took four different types of fiber supplements: psyllium, pectin, inulin, and wheat bran.

The analysis, published in the American Journal of Clinical Nutrition, showed that psyllium and pectin, respectively, were the most effective supplements. As for dosage, more than 10 grams of additional fiber or more per day proved to be the optimal supplementation for chronic constipation. The dosages in the meta-analysis ranged from 10.8 to 40 grams a day.

“The findings with psyllium are not novel or surprising,” William D. Chey, MD, FACG, professor gastroenterology and of nutrition sciences at Michigan Medicine, told Verywell via email. Chey was not involved with the analysis. “Multiple previous studies and meta-analyses have concluded that psyllium is an evidence-based treatment for chronic constipation.”

However, Chey was surprised to see pectin as significant method of constipation relief, since it’s often used for the opposite problem.

“Many doctors recommend bananas and pectin to treat diarrhea,” he said.

Why It Works

Dietary fiber is plant matter that is not digested or absorbed in the intestines, which means that it passes on through. There are two kinds of fiber: insoluble and soluble. Insoluble fiber does not absorb moisture, but speeds up the passage of food through the gut. Soluble fiber absorbs moisture, which makes stools softer and easier to pass.

Psyllium contains mostly soluble fiber, while pectin is primarily soluble fiber.

Psyllium, which is the active ingredient in such over-the-counter laxatives as Metamucil and Konsyl, was linked to the biggest improvements at an additional three bowel movements per week. This means psyllium appears to be as effective or even more effective than non-fiber constipation treatments, including stimulant laxatives, which are linked to an additional 2.5 bowel movements per week.

According to study researcher Eirini Dimidi, PhD, a registered dietitian and lecturer in nutritional sciences at King’s College London, the effects of fiber on constipation aren’t curative—if you stop consuming enough fiber, the constipation will likely come back.

How Much Fiber Do You Need?

Chey said people with constipation should consume a total of 20 to 30 grams of fiber each day.

“If someone isn’t taking much fiber, they are going to need more than 10 grams of psyllium per day,” Chey said, referring to the amount of fiber supplementation the study recommends. “On the other hand, if someone is already on a high fiber diet, adding a lot of psyllium isn’t likely to provide much additional benefit.”

Too much fiber—or too much fiber too soon—comes with side effects. Dimidi said the fermentation of fiber in your gut can lead to gas, bloating, and pressure.

If you’re going to begin taking fiber supplements or increasing the amount of fiber in your diet, she suggests you do it gradually.

What If Fiber Doesn’t Work?

“Fiber is a frequent first-line treatment for constipation,” Chey noted. “When fiber alone doesn’t work, it is often combined with other laxatives such as PEG [polyethylene glycol], magnesium oxide, or stimulants like senna or bisacodyl. Because stimulants often cause cramping and pain, I prefer to start with osmotic laxatives like PEG and magnesium oxide before stimulants.”

There are other types of fiber supplements available, such as calcium polycarbophil, methylcellulose, and inulin. But Chey said there’s not enough evidence supporting their efficacy.

What This Means For You

A daily fiber supplement can help treat chronic constipation. Psyllium, in particular, seems to help even more than other laxatives.

2 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. van der Schoot A, Drysdale C, Whelan K, Dimidi E. The effect of fiber supplementation on chronic constipation in adults: an updated systematic review and meta-analysis of randomized controlled trials. Am J Clin Nutr. Published online July 11, 2022. doi:10.1093/ajcn/nqac184

  2. Medlineplus. Soluble vs. insoluble fiber.

By Valerie DeBenedette
Valerie DeBenedette has over 30 years' experience writing about health and medicine. She is the former managing editor of Drug Topics magazine.