Psyllium
Summary
Psyllium lowered LDL cholesterol in 28 pooled trials, and FDA allows a heart-health claim for psyllium husk soluble fiber. It also lowered blood-sugar markers, softened stools and modestly lowered systolic pressure; weight results conflict. Taken with too little fluid, it can swell and cause choking, and MedlinePlus advises spacing it from some medicines.
Key facts
- No head-to-head human data between powders, capsules and wafers in our sources[1]
- LDL cholesterol ↓ (A); blood-sugar markers ↓ (B); stool water and output ↑ vs docusate (C); systolic pressure ↓ small (C); body weight: conflicting (C)[1][2][4][3][5][8]
- Authorised claim (21 CFR 101.81) for diets low in saturated fat and cholesterol that include 7 g or more per day of soluble fiber from psyllium seed husk; a qualifying food must supply at least 1.7 g per serving[10]
- FDA requires a choking warning and 'at least 8 ounces (a full glass) of water or other fluid' directions on dry psyllium products[11][12]
- 6 graded human outcomes on this page
- October 9, 2026
How it works
EstablishedPsyllium is a predominantly soluble fiber that forms a viscous gel when hydrated and is not digested or fermented. In the small intestine the gel increases the viscosity of gut contents, slowing the breakdown and absorption of nutrients; as a bulk-forming laxative it absorbs liquid in the intestines and forms a bulky stool (established).[5][13]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Heart | Grade A | Worsened | Meta-analysis · n = 1,924 · 2018 | 2 rows |
| Metabolic | Grade B | Worsened | Meta-analysis · n = 962 · 2024 | 2 rows |
| Gut | Grade C | Improved | RCT · n = 170 · 1998 | 2 rows |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| LDL cholesterol, non-HDL cholesterol and apoB | Worsened | Grade A | Meta-analysis · n = 1,924 · 2018 Participants in 28 RCTs, with or without hypercholesterolemia Form: Psyllium (Plantago ovata) fiber · Dose: Median about 10.2 g/day · Duration: Not stated in the abstract LDL cholesterol fell by 0.33 mmol/L, non-HDL cholesterol by 0.39 mmol/L and apoB by 0.05 g/L versus control. Certainty was moderate for LDL and non-HDL (downgraded for inconsistency) and high for apoB. | 30239559 (opens PubMed)Source [1] |
| Fasting blood sugar, HbA1c and insulin resistance | Worsened | Grade B | Meta-analysis · n = 962 · 2024 Adults in 19 RCTs Form: Psyllium · Dose: Varied; subgroups below and above 10 g/day · Duration: Varied; fasting blood sugar not significant in trials shorter than 50 days Fasting blood sugar fell by 6.89 mg/dL, HbA1c by 0.75 and HOMA-IR by 1.17 versus placebo; insulin did not change significantly. HbA1c was not significantly lower with less than 10 g/day. | 38844885 (opens PubMed)Source [2] |
| Systolic blood pressure | Worsened | Grade C | Meta-analysis · n = 592 · 2020 Participants in 11 RCTs Form: Psyllium · Dose: Not stated in the abstract · Duration: Not stated in the abstract Systolic blood pressure fell by 2.04 mmHg; the effect was stronger in people with higher starting blood pressure. | 32066221 (opens PubMed)Source [3] |
| Body weight, BMI and waist size | Mixed | Grade C | Meta-analysis · n = 354 · 2023 Participants with overweight or obesity in 6 RCTs of at least 2 months Form: Psyllium taken just before meals · Dose: Mean 10.8 g/day · Duration: Mean 4.8 months Body weight fell by 2.1 kg, BMI by 0.8 and waist by 2.2 cm. A separate meta-analysis of 22 RCTs found no significant change in weight, BMI or waist, so the overall picture is conflicting. | 37163454 (opens PubMed)Source [5] |
| Stool water content, stool output and bowel-movement frequency | Improved | Grade C | RCT · n = 170 · 1998 Adults with chronic idiopathic constipation Form: Psyllium hydrophilic mucilloid vs docusate sodium (active comparator, double-blind) · Dose: 5.1 g twice daily · Duration: 2 weeks Psyllium raised stool water content (2.33% vs 0.01%), stool water weight and total stool output (359.9 vs 271.9 g/week) more than docusate. Bowel movements were more frequent in week 2 (3.5 vs 2.9 per week) but not in week 1. | 9663731 (opens PubMed)Source [4] |
| Weekly complete bowel movements and straining | Mixed | Grade D | RCT · n = 75 · 2021 US adults with chronic constipation (partially randomized; 22 in the psyllium group) Form: Psyllium vs green kiwifruit vs prunes (no placebo) · Dose: 12 g/day · Duration: 4 weeks Responder rates were similar across the three treatments; all three raised weekly complete bowel movements from baseline. Straining improved with psyllium, but stool consistency improved only with kiwifruit and prunes. Adverse events were most common with psyllium. | 34074830 (opens PubMed)Source [6] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Psyllium husk powder or granules | Varies[10] | No head-to-head human data[1] | Must be mixed with at least 8 ounces of liquid; inhaling the powder while mixing can cause allergic reactions.[11][13] | LDL cholesterol, blood sugar, stool output |
| Capsules and wafers | Varies[13] | No head-to-head human data[1] | Dry dosage forms carry the same FDA choking warning and full-glass-of-fluid directions; wafers should be chewed thoroughly.[11][13] | Not compared separately in our sources |
Studied doses
Doses studied in human trials ranged from about 10.2 to 12 g of psyllium a day, for 2 weeks (constipation) to a mean of 4.8 months (weight); a 28-trial lipid meta-analysis used a median of about 10.2 g/day, and FDA's heart-health claim is based on 7 g or more of psyllium husk soluble fiber a day.[4][6][5][1][10]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
Medicines
- Digoxin, salicylates (aspirin) and nitrofurantoinNIH fact sheetMedlinePlus advises not taking these within 3 hours of psyllium and telling a doctor or pharmacist about all medicines, because doses may need to change.[13]
- DigoxinRCTIn a randomized study of 30 older in-patients on digoxin (14 given an ispaghula product, 16 wheat bran), the ispaghula product did not change steady-state digoxin levels over 4 weeks.[9]
- Blood-sugar-lowering medicinesReviewThe largest glucose reductions were seen in people already on blood-sugar treatment; the authors say more study is needed on how to combine psyllium with blood-sugar-lowering medicines.[7]
Who should be careful
- Difficulty swallowing
- FDA-required labeling: taking this product without adequate fluid may cause it to swell and block the throat or esophagus and may cause choking; it should not be taken by people who have difficulty swallowing. Chest pain, vomiting, or difficulty swallowing or breathing afterwards needs immediate medical attention.[11][12]
- Too little fluid
- FDA-required directions: take or mix with at least 8 ounces (a full glass) of water or other fluid.[11]
- Bowel or swallowing problems
- MedlinePlus advises telling a doctor first about intestinal blockage, rectal bleeding or difficulty swallowing, among other conditions.[13]
- Allergy
- Inhaling psyllium powder while mixing can cause allergic reactions (MedlinePlus).[13]
- Before you start
- Talk to your pharmacist or clinician before adding this supplement, especially if you take prescription medicines, are pregnant or breastfeeding, or have a chronic health condition.[13]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Articles about Psyllium
Plain-English answers to common questions, built on the evidence above.
Frequently asked questions
What exactly does FDA's psyllium heart-health claim say?
The model claim in 21 CFR 101.81(e)(1), with brackets the manufacturer fills in, reads: “Soluble fiber from foods such as [name of soluble fiber source from paragraph (c)(2)(ii) of this section and, if desired, the name of food product], as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease. A serving of [ name of food] supplies ________ grams of the [grams of soluble fiber specified in paragraph (c)(2)(i)(G) of this section] soluble fiber from [name of the soluble fiber source from paragraph (c)(2)(ii) of this section] necessary per day to have this effect.”[10]
How much psyllium does that claim require?
21 CFR 101.81 specifies 7 g or more per day of soluble fiber from psyllium seed husk, a food that supplies at least 1.7 g per serving, and diets low in saturated fat and cholesterol. It is a food-labeling claim about diets, not an approval of psyllium as a drug.[10]
How much does psyllium lower cholesterol?
Across 28 trials (1,924 participants), a median of about 10.2 g/day lowered LDL cholesterol by 0.33 mmol/L (moderate-certainty evidence) and apoB by 0.05 g/L (high certainty).[1]
Does psyllium help with constipation?
In a 2-week trial of 170 adults, psyllium raised stool water content and stool output more than the stool softener docusate. In a 4-week comparison, psyllium, kiwifruit and prunes gave similar responder rates, and adverse events were most common with psyllium.[4][6]
Does psyllium help with weight loss?
The evidence conflicts: a 2023 meta-analysis of 6 trials (354 people) taking psyllium before meals found about 2.1 kg more weight loss, but a 2020 meta-analysis of 22 trials found no significant change in weight, BMI or waist size.[5][8]
How should psyllium be taken safely?
FDA-required directions say to take or mix it with at least 8 ounces (a full glass) of water or other fluid, because too little liquid may cause choking, and people with difficulty swallowing should not take it. MedlinePlus adds that, as a laxative, it should not be used for longer than 1 week unless a doctor advises it.[11][13]
Does psyllium interact with medicines?
MedlinePlus advises spacing digoxin, aspirin and nitrofurantoin at least 3 hours from psyllium. A small randomized study found no change in digoxin levels with an ispaghula laxative. People on blood-sugar-lowering medicines saw the largest glucose changes in trials.[13][9][7]
Sources
- [1]Effect of psyllium (Plantago ovata) fiber on LDL cholesterol and alternative lipid targets, non-HDL cholesterol and apolipoprotein B: a systematic review and meta-analysis of randomized controlled trials.. Am J Clin Nutr, 2018. meta-analysis
- [2]The effect of psyllium on fasting blood sugar, HbA1c, HOMA IR, and insulin control: a GRADE-assessed systematic review and meta-analysis of randomized controlled trials.. BMC Endocr Disord, 2024. meta-analysis
- [3]The effect of psyllium supplementation on blood pressure: a systematic review and meta-analysis of randomized controlled trials.. Korean J Intern Med, 2020. meta-analysis
- [4]Psyllium is superior to docusate sodium for treatment of chronic constipation.. Aliment Pharmacol Ther, 1998. RCT
- [5]Psyllium is a natural nonfermented gel-forming fiber that is effective for weight loss: A comprehensive review and meta-analysis.. J Am Assoc Nurse Pract, 2023. meta-analysis
- [6]Exploratory Comparative Effectiveness Trial of Green Kiwifruit, Psyllium, or Prunes in US Patients With Chronic Constipation.. Am J Gastroenterol, 2021. RCT
- [7]Psyllium fiber improves glycemic control proportional to loss of glycemic control: a meta-analysis of data in euglycemic subjects, patients at risk of type 2 diabetes mellitus, and patients being treated for type 2 diabetes mellitus.. Am J Clin Nutr, 2015. meta-analysis
- [8]The effects of psyllium supplementation on body weight, body mass index and waist circumference in adults: A systematic review and dose-response meta-analysis of randomized controlled trials.. Crit Rev Food Sci Nutr, 2020. meta-analysis
- [9]Influence of wheat bran and of a bulk-forming ispaghula cathartic on the bioavailability of digoxin in geriatric in-patients.. Drug Nutr Interact, 1987. RCT
- [10]21 CFR 101.81 Health claims: Soluble fiber from certain foods and risk of coronary heart disease (CHD) (eCFR, up to date as of 2026-10-07). U.S. Food and Drug Administration (Code of Federal Regulations), 2023. label
- [11]21 CFR 201.319 Water-soluble gums, hydrophilic gums, and hydrophilic mucilloids ... required warnings and directions (eCFR, up to date as of 2026-10-07). U.S. Food and Drug Administration (Code of Federal Regulations), 2007. label
- [12]21 CFR 101.17(f) Food labeling warning statements: Foods containing psyllium husk (eCFR, up to date as of 2026-10-07). U.S. Food and Drug Administration (Code of Federal Regulations), 1977. label
- [13]Psyllium (MedlinePlus drug information; Last Revised 06/20/2024). U.S. National Library of Medicine (MedlinePlus; AHFS consumer information), 2024. fact-sheet
What changed
- First draft. Every evidence-row PMID checked with NCBI E-utilities (esummary + efetch abstract) and re-read in an independent adversarial pass.