Fiber Supplements: Which Type to Buy, and What It Costs (2026)
For constipation, the fiber supplement to buy is plain psyllium. It has the best evidence of any fiber. Most adults eat about 16.6 g of fiber a day, short of the 25 to 38 g they need, so food comes first.
Safety: Take psyllium with a full glass of water. Do not take it if you have trouble swallowing. Take other medicines 2 hours before or after. All the cautions.
Is a fiber supplement worth taking?
- For constipation, yes, if it is psyllium. In a review of trials, about two in three people responded to fiber against about two in five on a control, and only doses of more than 10 g a day worked (van der Schoot 2022). US gut doctors could find trials for three fibers (psyllium, bran and inulin), and only psyllium appears to be effective (AGA-ACG 2023).
- To reach your daily target, food comes first: beans, whole grains, fruit, vegetables and nuts (NIDDK). A supplement fills part of the gap.
Which type
Fiber that forms a gel and resists fermentation holds water in stool and softens it; psyllium and methylcellulose (Citrucel) work this way (McRorie and McKeown 2017; Dellschaft 2026). Wheat dextrin (Benefiber) and inulin dissolve and are fermented by gut bacteria: neither acts as a laxative (McRorie and McKeown 2017), and in trials inulin did not raise bowel movements and made gas worse at 12 to 15 g a day (BDA 2025). Every type compared.
How much
Aim for 25 g a day (women) or 38 g (men) up to age 50, and 21 g or 30 g after, from food and supplements together (IOM 2002). For a supplement, start with one serving a day and build up to 2 or 3, each in at least 8 oz of water (Metamucil label; 21 CFR 201.319). Find your target and your gap.
Side effects and cautions
- Gas and bloating are the main side effects (AGA-ACG 2023). Build up slowly.
- Choking. Bulk fibers like psyllium swell; taken with too little liquid they can block the throat. Take each serving with a full glass of water. Do not take it if you have trouble swallowing. Get help at once for chest pain, vomiting, or trouble swallowing or breathing after a dose (21 CFR 201.319).
- Medicines. Take them 2 or more hours before or after a fiber laxative (Metamucil label).
- Ask a doctor first if you are pregnant or breast-feeding, or before giving fiber to a child (Metamucil label).
- See a doctor if constipation lasts more than 7 days, or with rectal bleeding (Metamucil label).
Which fiber to buy
Our pick for most people, Konsyl Daily Psyllium Fiber Powder, is at the top of the page. 10 of the 36 fiber supplements we score are on a public testing list. By need:
- Buy NOW Whole Psyllium Husks (16 oz) on Amazon
- Buy Tomorrow's Nutrition Sunfiber (PHGG) on Amazon
- Buy vitafusion FiberWell Sugar Free Fiber Gummies (90 count) on Amazon
- Buy Metamucil 4-in-1 Psyllium Powder, Sugar-Free Orange on Amazon
- Buy Benefiber Prebiotic Fiber Powder, Unflavored (wheat dextrin) on Amazon
- Buy NOW Organic Inulin Prebiotic Powder (8 oz) on Amazon
If psyllium gives you gas, try methylcellulose, a fiber gut bacteria do not ferment (Dellschaft 2026): Citrucel Methylcellulose Fiber Powder.
| Item | Value |
|---|---|
| NOW whole husk | $0.51 |
| vitafusion gummies | $0.60 |
| NOW inulin | $0.75 |
| Konsyl psyllium | $0.87 |
| Metamucil sugar-free | $0.88 |
| Benefiber wheat dextrin | $1.07 |
| Sunfiber PHGG | $1.39 |
Our picks, scored, with cost per 10 g of fiber and testing list. Scores compare products only inside a group (psyllium powders, other powders, capsules, gummies), so a gummy’s 10/10 is not better than a powder’s 9/10.
Other uses
- For IBS, US guidelines advise soluble fiber such as psyllium over bran. In trials, about 1 in 7 people improved who would not have on a placebo (ACG 2021; Moayyedi 2014). Ask your doctor first.
- For heart health, FDA allows this health claim: diets low in saturated fat and cholesterol that include 7 g of soluble fiber a day from psyllium husk may reduce the risk of heart disease (21 CFR 101.81).
Fiber guides
How much
Which type
Which product
How we checked this
Products. We read 56 fiber products and could score 36. Every score, and why some are not scored.
Testing lists. We read NSF/ANSI 173, NSF Certified for Sport and Informed Choice in full on October 6, 2026. USP Verified and Informed Sport as listed on September 22, 2026.
Prices. Each brand’s own list price, or a named store where the brand sells none itself. Amazon’s price can differ.
Sources
- Institute of Medicine. Dietary Reference Intakes for fiber, 2002 (National Academies’ summary). USDA What We Eat in America, NHANES 2017 to March 2020. NIDDK, Eating, diet and nutrition for constipation. All read October 6, 2026.
- van der Schoot A, et al. Am J Clin Nutr. 2022. PubMed 35816465. Chang L, et al. (AGA-ACG 2023). Gastroenterology. 2023. PubMed 37211380. Dimidi E, et al. (BDA 2025). J Hum Nutr Diet. 2025. PubMed 41081513
- Lacy BE, et al. (ACG 2021). Am J Gastroenterol. 2021. PubMed 33315591. Moayyedi P, et al. Am J Gastroenterol. 2014. PubMed 25070054
- Jovanovski E, et al. Am J Clin Nutr. 2018. PubMed 30239559. McRorie JW Jr, McKeown NM. J Acad Nutr Diet. 2017. PubMed 27863994 (McRorie is listed at Procter & Gamble, which makes Metamucil, on a 2015 paper (Gibb 2015, PubMed 26561625).). Dellschaft N, et al. Aliment Pharmacol Ther. 2026. PubMed 42728685
- FDA. 21 CFR 201.319, eCFR, read October 6, 2026. Metamucil drug facts label, DailyMed, read October 6, 2026.
This page is for information. It is not medical advice.