“Fiber supplements relieve constipation.”
Fiber supplements relieve chronic constipation for many adults, with psyllium having the best evidence, but not every type of fiber works.
A daily fiber supplement, especially psyllium, is a reasonable first thing to try for ongoing constipation. It usually takes more than 10 grams a day and a few weeks to tell whether it works, and some fibers sold for gut health, such as inulin, mostly add gas.
Ask your clinician or pharmacist about a 4-week trial of daily psyllium, taken with a full glass of water.
Safety note: Take psyllium mixed with at least 8 ounces of liquid. Psyllium can affect some medicines: do not take digoxin, aspirin or nitrofurantoin within 3 hours of it.
Talk to a healthcare professional if: you have trouble swallowing or have had a bowel blockage, you get stomach pain, vomiting or trouble breathing after taking a fiber laxative, or you want to use one for more than a week.
Randomized trials show fiber supplements help many adults with chronic constipation, especially psyllium. Confidence is Moderate because the trials varied a lot, none was at low risk of bias in every area, and some fiber types did not help.
Fiber supplements relieve chronic constipation for many adults, with psyllium having the best evidence, but not every type of fiber works. In a 2022 review of 16 trials, 66% of people taking fiber improved, compared with 41% in the comparison groups. Benefits showed up mainly at more than 10 grams a day, and more frequent bowel movements mainly after at least 4 weeks.
Psyllium, pectin and wheat bran increased how often people had bowel movements. Inulin, polydextrose and galacto-oligosaccharides did not. Psyllium was the only fiber that clearly reduced straining. Fiber also made people more gassy, especially inulin. Results differed a lot between trials, and no trial was judged at low risk of bias in every area.
- 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. American Journal of Clinical Nutrition. 2022;116(4):953-969. DOI: 10.1093/ajcn/nqac184. PMID: 35816465. PMCID: PMC9535527
- MedlinePlus, National Library of Medicine (AHFS Patient Medication Information). Psyllium. Last revised June 20, 2024