Psyllium husk

What is psyllium?

Psyllium is the husk of the seed of Plantago ovata, a plant grown mainly in India. The husk is rich in soluble fiber that absorbs water and forms a soft gel in the gut. It is the active ingredient in many over-the-counter fiber products, and MedlinePlus describes it as a bulk-forming laxative that absorbs liquid in the intestines, swells and forms a bulky stool that is easier to pass. The same page notes that doctors sometimes use it for diarrhea or high cholesterol as well.

Because it is a soluble fiber, psyllium also belongs to the group that MedlinePlus says can help lower cholesterol, alongside oat bran, beans and some fruits.

What the research says

Psyllium has more human evidence for regularity than almost any other supplement ingredient. A 2022 systematic review and meta-analysis in the American Journal of Clinical Nutrition pooled 16 randomized trials with 1,251 adults with chronic constipation. Overall, 66% of people responded to fiber compared with 41% on control treatments, and psyllium was one of the two fiber types with significant effects on response and stool frequency. The authors noted that benefits appeared mainly with doses above 10 g per day and treatment lasting at least four weeks. Flatulence was more common with fiber.

A 2026 meta-analysis in Gastroenterology looked at fiber supplements in adults with irritable bowel syndrome (IBS). Across 16 trials reporting clinical response, 52% responded to fiber versus 44% to control, and psyllium specifically showed a benefit. Overall symptom scores, however, did not improve significantly across studies, which is a reminder that fiber helps some people more than others.

Head-to-head studies point the same way. In a 2021 US trial in adults with chronic constipation, psyllium at 12 g a day, prunes and green kiwifruit all increased complete bowel movements over four weeks. Side effects were most common with psyllium, mainly gas and bloating.

How it’s used in supplements

Fiber products typically provide several grams of psyllium per serving, mixed into a full glass of water. That is the range studied in trials. Gut “cleanse” capsules that list psyllium among ten or more ingredients usually contain far less, because a capsule only holds a few hundred milligrams of powder in total. If you want the documented benefits of psyllium, a plain psyllium product used as directed is the more direct route.

Start low and increase slowly to limit gas, and always take it with enough fluid. MedlinePlus advises drinking at least 8 ounces of liquid with each dose and separating psyllium from certain medicines, such as digoxin, salicylates and nitrofurantoin, by about three hours.

Psyllium is usually well tolerated over the long term, and it is often used daily under a doctor’s guidance. Common minor side effects include gas, bloating and a feeling of fullness, which usually ease as the body adjusts.