Best Fiber Supplement (2026): Ranked by Cost Per Gram of Fiber
Informational summary — not medical advice. Prices are live Amazon prices, verified July 13, 2026; they change.
The best fiber supplement isn't a brand — it's a type bought cheaply. Psyllium has the best evidence (the only fiber with an FDA heart claim, plus support for constipation and IBS), and bought as plain husk powder it's also the cheapest per gram of fiber. Top pick: NOW Psyllium Husk Powder, Organic (12 oz). Pick methylcellulose (Citrucel) instead only if psyllium makes you gassy, or inulin only to feed gut bacteria.
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| Item | Value |
|---|---|
| NOW Foods | $0.043 |
| NOW Foods | $0.053 |
| Konsyl | $0.058 |
| Benefiber | $0.073 |
| Metamucil | $0.074 |
| Citrucel | $0.310 |
The picks
NOW Psyllium Husk Powder, Organic (12 oz)
Plain organic psyllium husk: 7 g fiber (6 g soluble) per serving — just under the FDA 7 g/day soluble-fiber target in a single serving — at the lowest cost per gram in this list. The most evidence, the least fuss, the best price. Start here.
Check price on Amazon →Konsyl Daily Psyllium Fiber Powder (19 oz)
A single ingredient — psyllium husk — with no flavoring or sweeteners, at 90 servings. Nearly as cheap per gram as the top pick; the choice if you want psyllium and nothing else.
Check price on Amazon →Citrucel Methylcellulose Fiber Powder
Methylcellulose bulks and gels like psyllium but is not fermented at all, so it produces the least gas. The trade-off is honest: it is the priciest per gram here and is not a prebiotic — buy it specifically for low-gas regularity.
Check price on Amazon →The full ranking
Every product here, ranked by cost per gram of fiber. Remember the type column matters as much as the price: inulin is cheap but it's a prebiotic, not a bulking fiber, and wheat dextrin is a weak laxative — see fiber types compared.
| Product | Type | Fiber/serving | Price | Cost/g fiber | |
|---|---|---|---|---|---|
| NOW Foods — NOW Organic Inulin Prebiotic Powder (8 oz) | Inulin (prebiotic) | 3 g | $10.00 | $0.043 | Price → |
| NOW Foods — NOW Psyllium Husk Powder, Organic (12 oz) | Psyllium | 7 g | $14.10 | $0.053 | Price → |
| Konsyl — Daily Psyllium Fiber Powder (19 oz) | Psyllium | 5 g | $25.99 | $0.058 | Price → |
| Benefiber — Prebiotic Fiber Powder (wheat dextrin) | Wheat dextrin | 3 g | $13.48 | $0.073 | Price → |
| Metamucil — 4-in-1 Psyllium, Sugar-Free (72 servings) | Psyllium | 3.4 g | $17.97 | $0.074 | Price → |
| Citrucel — Methylcellulose Fiber Powder | Methylcellulose | 2 g | $18.59 | $0.310 | Price → |
NOW Organic Inulin Prebiotic Powder (8 oz) works out to about $0.04/gram of fiber — roughly 7× cheaper per gram than methylcellulose. With psyllium, the store brand and the powder are the smart buys; you pay a premium for flavor and packaging, not fiber.
How we ranked
We don't rank by tub size or brand recognition. Two things decide it:
- Fiber type & evidence first. A cheap fiber that doesn't do the job isn't a bargain. Psyllium leads because it has the evidence (FDA cholesterol claim; RCTs for constipation and IBS) and does all three fiber jobs — gels, resists fermentation, and bulks. Here's the breakdown.
- Then cost per gram of fiber. The honest value metric isn't price per tub — it's price ÷ grams of actual fiber, using each product's label serving. That's what the table above shows.
What we deliberately ignore: "prebiotic," "gut health," and "GLP-1 friendly" front-label marketing that isn't backed by the fiber type inside, and big milligram numbers that turn out to be small once you read the serving size.
Frequently asked questions
What is the best fiber supplement?
For most people, plain psyllium husk powder — the best-evidenced fiber (FDA heart claim; RCTs for constipation and IBS) and the cheapest per gram. Our pick is NOW Psyllium Husk Powder. Choose methylcellulose (Citrucel) if psyllium is gassy, or inulin only to feed gut bacteria.
Is Metamucil or generic psyllium better?
Same active ingredient — psyllium. Metamucil adds flavor/sweetener, costs more per gram of fiber, and delivers a bit less psyllium per serving. Fine for taste; plain psyllium husk powder wins on value.
What is the best fiber for the money?
Plain psyllium husk powder, ~4–6 cents per gram of fiber — several times cheaper than methylcellulose or branded blends. Inulin powder is similarly cheap but is a prebiotic, not a bulking fiber.
Related
- Fiber Types Compared — which fiber for constipation, cholesterol, IBS, or gut bacteria
- Fiber Dosage Guide — how much per day and how to ramp up
- Best Psyllium Supplement — a deeper psyllium-only ranking, including capsules and Metamucil
- All Fiber Guides
Sources
- van der Schoot A, et al. "The Effect of Fiber Supplementation on Chronic Constipation in Adults." Am J Clin Nutr. 2022. PMID: 35816465
- Nagarajan N, et al. "Fiber supplementation in irritable bowel syndrome." Eur J Gastroenterol Hepatol. 2015. PMID: 26148247
- McRorie JW Jr, McKeown NM. "Understanding the Physics of Functional Fibers in the Gastrointestinal Tract." J Acad Nutr Diet. 2017. PMID: 27863994
- U.S. FDA. "Health claims: Soluble fiber from certain foods and risk of coronary heart disease." 21 CFR 101.81.