Plantago ovata Forssk. (seed husk) · food
Evidence tier: strong
A foundational soluble fibre that works bidirectionally, bulks loose stools and softens hard ones.
Psyllium husk is a gel forming, poorly fermented soluble fibre. In water it swells into a viscous gel that persists through the whole colon. That single physical property does three things. It holds water in the stool, which softens hard stool and bulks loose stool, the reason the effect looks bidirectional. It traps bile acids and carries them out of the body, forcing the liver to pull cholesterol from the blood to make more, which is the accepted explanation for the LDL drop and the basis of the FDA claim. And it slows the release of carbohydrate from the gut, blunting the post meal glucose rise. Unlike most fibre mechanisms, this one is physical rather than speculative.
Strong, and it is one of the few ingredients in this catalogue that genuinely earns the word. Psyllium carries a US FDA AUTHORISED health claim, the highest regulatory bar there is, meeting the Significant Scientific Agreement standard: 21 CFR 101.81 permits foods to state that soluble fibre from psyllium seed husk, as part of a diet low in saturated fat and cholesterol, may reduce the risk of coronary heart disease. The regulation is specific: at least 7 g per day of soluble fibre from psyllium husk, at least 1.7 g per serving, from the dried seed coat of Plantago ovata at no less than 95 percent purity. Europe agrees. The EMA HMPC grants ispaghula husk WELL ESTABLISHED USE, not traditional use, for habitual constipation, for stool softening where easier defecation is desirable (anal fissure, haemorrhoids, after rectal surgery), as a fibre supplement in irritable bowel syndrome with constipation, and as an adjunct in hypercholesterolaemia under medical supervision. The lipid evidence is replicated: a 2024 systematic review and meta analysis of 29 randomised controlled trials in 2,769 participants found LDL cholesterol fell by about 0.35 mmol/L and total cholesterol by about 0.28 mmol/L, and a 2025 dose response meta analysis of 41 RCTs reached the same conclusion. The glycaemic evidence is real and dose dependent: a meta analysis of 35 controlled trials found that in people already treated for type 2 diabetes, psyllium taken before meals lowered fasting glucose by about 37 mg/dL and HbA1c by about 0.97 percent, with the effect scaling with how poor baseline control was. The honest caveats. For constipation, the outcome most consumers buy it for, the 2023 joint AGA and ACG guideline issues only a CONDITIONAL recommendation on LOW certainty evidence, while noting that psyllium is the fibre with the best data and the only one of bran, inulin and methylcellulose that clearly worked. For diarrhoea and faecal incontinence the data are thinner and most trials are underpowered, though a randomised trial found psyllium reduced incontinence episodes about as well as loperamide with less rebound constipation (10 percent versus 29 percent). So: strong overall, carried by the cholesterol and coronary heart disease claim and the glycaemic data, with the constipation use real but graded low certainty by the gastroenterology societies themselves.
For the coronary heart disease claim (FDA, 21 CFR 101.81): at least 7 g of soluble fibre from psyllium husk daily, delivered in servings of at least 1.7 g. Supplement practice runs 5 to 10 g of husk once or twice daily. Two rules are not optional. Take each dose with plenty of liquid: FDA requires the label to carry the notice that the product must be eaten with at least a full glass of liquid and that taking it without enough liquid may cause choking, and that it must not be taken by anyone with difficulty swallowing. And separate it from other oral medicines: the EMA instructs taking it at least half an hour to one hour before or after any other medicine, because the gel delays their absorption. Do not take it immediately before lying down to sleep.
5 to 10 g twice daily, taken with abundant water 1 hour from medications.
Onset: ~3 days
CRITICAL: take with at least 250ml water to prevent oesophageal obstruction. Separate from medications.
Pregnancy: caution
Breastfeeding: safe
Active compounds: arabinoxylan (gel forming soluble fibre), mucilage polysaccharides
Remedies using Psyllium · Browse by body system · Check it against what you take
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.