Does fiber lower cholesterol?

Yes, by a modest amount, and mostly the soluble, gel-forming kind. A Cochrane review of 17 randomized trials in 1,067 people found more fiber lowered total cholesterol by 8.9 mg/dL (0.23 mmol/L) and LDL cholesterol by 5.4 mg/dL (0.14 mmol/L), in trials that were mostly small and shorter than 12 weeks. A larger 2023 analysis of 181 trials in 14,505 adults found soluble fiber supplements lowered LDL by 8.28 mg/dL. Psyllium and oat beta-glucan each lowered LDL in their own meta-analyses. Wheat bran did not lower blood lipids.

Established. Soluble fiber lowers LDL cholesterol. Every meta-analysis of soluble fiber trials on this page points the same way, and each extra 5 g of soluble fiber a day lowered LDL by 5.57 mg/dL (95% CI 3.69 to 7.44) across 181 trials, a figure that comes from supplements rather than food.

What the trials found

Fiber in general

The Cochrane review pooled trials of increased dietary fiber in adults from the general population or at risk of heart disease. Total cholesterol fell by 8.9 mg/dL (95% CI 2.3 to 15; metric: 0.23 mmol/L, 0.06 to 0.40) and LDL by 5.4 mg/dL (95% CI 2.3 to 8.5; metric: 0.14 mmol/L, 0.06 to 0.22). Triglycerides did not change, and HDL fell by a very small 1.2 mg/dL (0.03 mmol/L). The reviewers rated the risk of bias as mostly unclear and reported no heart attacks or deaths, because the trials did not measure them. A 2019 Lancet series pooled 58 clinical trials with 4,635 adults and found lower total cholesterol at higher fiber intakes, without giving the size of the drop in its abstract.

Soluble fiber, where the effect lives

The 181-trial analysis found soluble fiber supplements lowered LDL by 8.28 mg/dL (95% CI 5.18 to 11.38) and total cholesterol by 10.82 mg/dL, and its authors flag high heterogeneity and publication bias. An older 1999 analysis of 67 controlled trials, some of them not randomized, found each gram of soluble fiber lowered LDL by 2.2 mg/dL (0.057 mmol/L). At usual intakes that is a small effect. That analysis found pectin, oat bran, guar gum and psyllium behaved alike. A 2026 review of 50 trials of related gums found guar gum moved blood lipids more consistently than fenugreek, without pooling a number.

Psyllium gives the clearest single result. In 28 randomized trials with 1,924 people, a median of about 10.2 g a day lowered LDL by 13 mg/dL (95% CI 10 to 15; metric: 0.33 mmol/L, 0.27 to 0.38), on moderate-quality evidence. Oat beta-glucan at a median of 3.5 g a day lowered LDL by 7.3 mg/dL (95% CI 5.4 to 8.9; metric: 0.19 mmol/L, 0.14 to 0.23) across 58 trials with 3,974 people, with large unexplained differences between trials.

Myth. Any fiber will lower cholesterol. A network meta-analysis of 55 trials with 3,900 people ranked oat bran first, lowering LDL by 12 mg/dL (0.32 mmol/L), and found barley, brown rice, wheat and wheat bran ineffective against control. Insoluble wheat fiber did not lower cholesterol in these trials.

In people already being treated

In people with type 2 diabetes, 38 randomized trials found soluble fiber lowered LDL by 11.14 mg/dL (95% CI 6.87 to 15.41). In three short trials of 4 to 12 weeks in people on statins, adding psyllium lowered LDL as much as doubling the statin dose would, and the abstract gives no figure in mmol/L. Three trials is a small base, and it is a reason to discuss psyllium with a doctor, never to change a statin dose on your own.

In eight trials of 656 people with mildly to moderately raised cholesterol who were already on a low-fat diet, about 10.2 g of psyllium a day lowered LDL by a further 7 percent against a cellulose placebo, as the review abstract reports.

Unsettled. Whether eating more fiber prevents heart attacks is a separate question, and the trials on this page cannot answer it. They were mostly shorter than 12 weeks and none reported heart disease events. The link with fewer heart attacks comes from observational studies, which cannot show that the fiber is the cause.

Who should be careful

Not for everyone. If you take levothyroxine for your thyroid, the FDA-approved label says dietary fiber may bind the drug and lower its absorption. A big change in how much fiber you eat, or starting a fiber supplement, is worth mentioning to the person who checks your thyroid levels.

Gut symptoms are the usual cost. In the Cochrane review's 23 trials with 1,513 people, side effects were mostly mild to moderate stomach and bowel complaints, reported more often with fiber than control, though not every trial reported them and no rate was pooled. A review that pooled safety data from 19 studies of 6 weeks to 6 months found psyllium well tolerated alongside a low-fat diet.

Dry psyllium, guar gum and similar powders sold as laxatives must carry a US choking warning. Federal rules say they can block the esophagus when taken without enough fluid, or by people who have difficulty swallowing or a narrowed esophagus. That rule covers powdered products, and fiber in ordinary food is outside it.

If you take a statin, the psyllium result above is an add-on to treatment and never a replacement for it.

What expert bodies say

The US FDA allows the heart health claim for soluble fiber from oats or barley only when a food supports an intake of 3 g or more of beta-glucan soluble fiber a day. The EU authorizes the claim that oat beta-glucan lowers blood cholesterol, and it has no authorized claim of that kind for fiber in general.

The US Dietary Reference Intake is 14 g of fiber per 1,000 calories, or 25 g a day for adult women and 38 g for men, against a usual US intake of only 15 g. The American Dietetic Association notes that the figure follows recommended energy intake and population studies of heart disease. No clinical fiber trial set it. The 2019 Lancet series found risk reduction across a range of critical outcomes was greatest at intakes between 25 g and 29 g a day.

How we searched

What would change this answer

• A long trial of fiber that counts heart attacks, strokes and deaths. The LDL effect is consistent, and the Cochrane review found no trial data on these events.
• An update of the Cochrane fiber review. We found no synthesis newer than the 2023 dose-response analysis.
• Trials longer than 12 weeks that use food rather than supplements, so the size of the effect from an ordinary diet can be measured directly.

The two foods with the best evidence have their own pages: psyllium and cholesterol, oats and cholesterol and oat bran and cholesterol. The product itself is on the psyllium husk page, and the rest of the nutrient is in the fiber guide.

Sources

1. ev-fibchol-01 · Meta-analysis or systematic review · Cochrane systematic review and meta-analysis of randomized controlled trials · n = 1067
   Results on lipids suggest there is a significant beneficial effect of increased fibre on total cholesterol levels (17 trials (20 comparisons), 1067 participants randomised, mean difference -0.23 mmol/L, 95% CI -0.40 to -0.06), and LDL cholesterol levels (mean difference -0.14 mmol/L, 95% CI -0.22 to -0.06) but not on triglyceride levels (mean difference 0.00 mmol/L, 95% CI -0.04 to 0.05), and there was a very small but statistically significant decrease rather than increase in HDL levels with increased fibre intake (mean difference -0.03 mmol/L, 95% CI -0.06 to -0.01).
   
   Who: adults at risk of cardiovascular disease or from the general population, 17 RCTs (20 comparisons)
   Effect: total cholesterol MD -8.9 mg/dL (95% CI -15 to -2.3; metric: -0.23 mmol/L, -0.40 to -0.06); LDL MD -5.4 mg/dL (95% CI -8.5 to -2.3; metric: -0.14 mmol/L, -0.22 to -0.06); triglycerides no change
   Certainty: Risk of bias mostly unclear, studies small and short (mostly up to 12 weeks); CVD events not reported.
   Cochrane Database Syst Rev, 2016 · checked 2026-10-07 · we read the abstract
2. ev-fibchol-02 · Meta-analysis or systematic review · Cochrane systematic review of randomized controlled trials · n = 1513
   Adverse events, where reported, appeared to mostly reflect mild to moderate gastrointestinal side-effects and these were generally reported more in the fibre intervention groups than the control groups.
   
   Who: adults in 23 RCTs of increased dietary fiber
   Effect: mild to moderate gastrointestinal side effects, more frequent in fiber groups; not pooled
   Certainty: Not all studies reported adverse events; the frequency was not pooled.
   Cochrane Database Syst Rev, 2016 · checked 2026-10-07 · we read the abstract
3. ev-fibchol-03 · Meta-analysis or systematic review · systematic review and dose-response meta-analysis of randomized controlled trials with GRADE · n = 14505
   There was a significant reduction in LDL cholesterol (MD: -8.28 mg/dL, 95% CI: -11.38, -5.18), total cholesterol (TC) (MD: -10.82 mg/dL, 95% CI: -12.98, -8.67), TGs (MD: -5.55 mg/dL, 95% CI: -10.31, -0.79), and apolipoprotein B (Apo-B) (MD: -44.99 mg/L, 95% CI: -62.87, -27.12) after soluble fiber supplementation in the overall analysis.
   
   Who: adults in 181 RCTs (220 treatment arms) of soluble fiber supplementation
   Effect: LDL MD -8.28 mg/dL (95% CI -11.38 to -5.18); total cholesterol -10.82 mg/dL (-12.98 to -8.67); apoB -44.99 mg/L
   Certainty: The authors point to high heterogeneity and publication bias.
   Adv Nutr, 2023 · checked 2026-10-07 · we read the abstract
4. ev-fibchol-04 · Meta-analysis or systematic review · dose-response meta-analysis of randomized controlled trials · n = 14505
   Each 5 g/d increase in soluble fiber supplementation had a significant reduction in TC (MD: -6.11 mg/dL, 95% CI: -7.61, -4.61) and LDL cholesterol (MD: -5.57 mg/dl, 95% CI: -7.44, -3.69).
   
   Who: adults in 181 RCTs of soluble fiber supplementation, dose-response analysis
   Effect: per 5 g/day soluble fiber: LDL -5.57 mg/dL (95% CI -7.44 to -3.69); total cholesterol -6.11 mg/dL (-7.61 to -4.61)
   Certainty: Supplements, not food; linearity outside the range of the studies was not tested.
   Adv Nutr, 2023 · checked 2026-10-07 · we read the abstract
5. ev-fibchol-05 · Observational data · meta-analysis of controlled trials, randomized and non-randomized · n = 67 trials
   Soluble fiber, 2-10 g/d, was associated with small but significant decreases in total cholesterol [-0.045 mmol L(-1).g soluble fiber(-1) (95% CI: -0.054, -0.035)] and LDL cholesterol [-0.057 mmol.L(-1).g(-1) (95% CI: -0.070, -0.044)].
   
   Who: participants in 67 controlled trials of pectin, oat bran, guar gum and psyllium at 2-10 g/day soluble fiber
   Effect: LDL -2.2 mg/dL (-0.057 mmol/L) per g soluble fiber (95% CI -0.070 to -0.044); total cholesterol -1.7 mg/dL (-0.045 mmol/L) per g
   Certainty: Old meta-analysis; it also included nonrandomized controlled studies, hence C, not A. The type of soluble fiber (oat, psyllium, pectin) did not affect the result.
   Am J Clin Nutr, 1999 · checked 2026-10-07 · we read the abstract
6. ev-fibchol-06 · Meta-analysis or systematic review · systematic review and meta-analysis of randomized controlled trials with GRADE · n = 1924
   Supplementation of a median dose of ∼10.2 g psyllium significantly reduced LDL cholesterol (MD = -0.33 mmol/L; 95% CI: -0.38, -0.27 mmol/L; P < 0.00001), non-HDL cholesterol (MD = -0.39 mmol/L; 95% CI: -0.50, -0.27 mmol/L; P < 0.00001), and apoB (MD = -0.05 g/L; 95% CI: -0.08, -0.03 g/L; P < 0.0001).
   
   Who: people with or without hypercholesterolemia in 28 RCTs of at least 3 weeks, median psyllium dose about 10.2 g/day
   Effect: LDL MD -13 mg/dL (95% CI -15 to -10; metric: -0.33 mmol/L, -0.38 to -0.27); non-HDL -15 mg/dL (-0.39 mmol/L); apoB -0.05 g/L; GRADE moderate for LDL
   Certainty: Psyllium is the strongest example of viscous soluble fiber; the LDL rating was downgraded for heterogeneity.
   Am J Clin Nutr, 2018 · checked 2026-10-07 · we read the abstract
7. ev-fibchol-07 · Meta-analysis or systematic review · systematic review and meta-analysis of randomized controlled trials · n = 3974
   A median dose of 3·5 g/d of oat β-glucan significantly lowered LDL-cholesterol (-0·19; 95 % CI -0·23, -0·14 mmol/l, P<0·00001), non-HDL-cholesterol (-0·20; 95 % CI -0·26, -0·15 mmol/l, P<0·00001) and apoB (-0·03; 95 % CI -0·05, -0·02 g/l, P<0·0001) compared with control interventions.
   
   Who: participants in 58 RCTs of at least 3 weeks of oat beta-glucan-enriched diets, median dose 3.5 g/day
   Effect: LDL -7.3 mg/dL (95% CI -8.9 to -5.4; metric: -0.19 mmol/L, -0.23 to -0.14); non-HDL -7.7 mg/dL (-0.20 mmol/L); apoB -0.03 g/L; I2 79% for LDL
   Certainty: Substantial unexplained heterogeneity.
   Br J Nutr, 2016 · checked 2026-10-07 · we read the abstract
8. ev-fibchol-08 · Meta-analysis or systematic review · pairwise and network meta-analysis of randomized trials · n = 3900
   Barley, brown rice, wheat and wheat bran were shown to be ineffective in improving blood lipid compared with control.
   
   Who: participants in 55 trials of whole grains and brans
   Effect: oat bran LDL -12 mg/dL (95% CI -17 to -7.3; metric: -0.32 mmol/L, -0.44 to -0.19); barley, brown rice, wheat and wheat bran ineffective versus control
   Certainty: Against the myth "any fiber lowers cholesterol": insoluble wheat fiber does not lower it.
   Eur J Nutr, 2019 · checked 2026-10-07 · we read the abstract
9. ev-fibchol-09 · Meta-analysis or systematic review · systematic review and meta-analysis of randomized controlled trials · n = 38 trials
   Results indicated that soluble fiber significantly altered TG (WMD: -16.97 mg/dL, 95 % CI: -29.16 to -4.78, P = 0.021), HDL-C (WMD: 1.74 mg/dL, 95 % CI: 1.02-2.46, P < 0.001), LDL-C (WMD: -11.14 mg/dL, 95 % CI: -15.41 to -6.87, P < 0.001), and TC (WMD: -13.87 mg/dL, 95 % CI: -17.99 to -9.75, P = 0.027).
   
   Who: patients with type 2 diabetes in 38 RCTs of soluble fiber
   Effect: LDL WMD -11.14 mg/dL (95% CI -15.41 to -6.87); total cholesterol -13.87 mg/dL; TG -16.97 mg/dL; HDL +1.74 mg/dL
   Certainty: There is no evidence quality assessment in the abstract.
   Prostaglandins Other Lipid Mediat, 2025 · checked 2026-10-07 · we read the abstract
10. ev-fibchol-10 · Meta-analysis or systematic review · systematic review and meta-analysis of randomized controlled trials · n = 3 trials
    Adding psyllium fiber resulted in reductions in low-density lipoprotein-cholesterol equivalent to doubling the statin dose.
    
    Who: people receiving statins in 3 RCTs of 4-12 weeks, psyllium plus statin versus statin alone
    Effect: LDL reduction with psyllium added equivalent to doubling the statin dose (p = 0.001)
    Certainty: Only three short RCTs; the abstract does not give the exact difference in mmol/L. Not a replacement for a statin.
    Am J Cardiol, 2018 · checked 2026-10-07 · we read the abstract
11. ev-fibchol-11 · Meta-analysis or systematic review · meta-analysis of randomized placebo-controlled trials with pooled safety data · n = 656
    Psyllium is well tolerated and safe when used adjunctive to a low-fat diet in individuals with mild-to-moderate hypercholesterolemia.
    
    Who: men and women with mild-to-moderate hypercholesterolemia on a low-fat diet, 384 psyllium and 272 placebo; safety from 19 studies of 6 weeks to 6 months
    Effect: total cholesterol -4%, LDL -7%, apoB/apoA-I -6% versus cellulose placebo; no effect on HDL or triglycerides
    Certainty: Safety pooled from 19 studies lasting 6 weeks to 6 months; no adverse event frequency in the abstract. No full text in PMC.
    Am J Clin Nutr, 2000 · checked 2026-10-07 · we read the abstract
12. ev-fibchol-12 · Meta-analysis or systematic review · series of systematic reviews and meta-analyses of prospective studies and randomized trials · n = 4635
    Clinical trials show significantly lower bodyweight, systolic blood pressure, and total cholesterol when comparing higher with lower intakes of dietary fibre.
    
    Who: adults without chronic disease in 58 clinical trials and 185 prospective studies
    Effect: significantly lower total cholesterol with higher versus lower fiber intake; size not given in the abstract; certainty for fiber moderate
    Certainty: Effect size on cholesterol not given in the abstract; no full text in PMC (no_pmc).
    Lancet, 2019 · checked 2026-10-07 · we read the abstract
13. ev-fibchol-13 · Position of an expert body · FDA-approved drug label, drug interactions section · n = —
    Soybean flour, cottonseed meal, walnuts, and dietary fiber may bind and decrease the absorption of levothyroxine sodium from the gastrointestinal tract.
    
    Who: people taking levothyroxine
    Effect: decreased levothyroxine absorption with dietary fiber
    Certainty: Label text; in practice: steady intake and TSH monitoring when the diet changes.
    Levothyroxine sodium, FDA-approved label (DailyMed), effective 2026-03-24 · checked 2026-10-07 · we read the section
14. ev-fibchol-14 · Position of an expert body · federal regulation text · n = —
    ( 1 ) 3 g or more per day of β-glucan soluble fiber from either whole oats or barley, or a combination of whole oats and barley.
    
    Who: 21 CFR 101.81(c), soluble fiber from certain foods and coronary heart disease
    Effect: qualifying intake: 3 g/day or more of beta-glucan soluble fiber from whole oats or barley
    Certainty: Regulatory decision, not an effect assessment.
    21 CFR 101.81, Health claims: Soluble fiber from certain foods and risk of coronary heart disease (CHD) · checked 2026-10-07 · we read the section
15. ev-fibchol-15 · Position of an expert body · regulatory register entry · n = —
    POL-HC-6248 Oat beta-glucan Oat beta-glucan has been shown to lower/reduce blood cholesterol. High cholesterol is a risk factor in the development of coronary heart disease -/- Authorised
    
    Who: EU Register of nutrition and health claims, claim POL-HC-6248
    Effect: authorized
    Certainty: The conditions of use of the claim are not given in the register snapshot.
    EU Register on nutrition and health claims, claim POL-HC-6248, snapshot 2026-09-21 · checked 2026-10-07 · we read the dataset
16. fib-t2 · Meta-analysis or systematic review · meta-analysis of randomized controlled trials inside the same review · n = 4,635
    Clinical trials show significantly lower bodyweight, systolic blood pressure, and total cholesterol when comparing higher with lower intakes of dietary fibre. Risk reduction associated with a range of critical outcomes was greatest when daily intake of dietary fibre was between 25 g and 29 g.
    
    Who: adults in 58 clinical trials
    Effect: lower bodyweight, systolic blood pressure and total cholesterol at higher fiber intakes; greatest risk reduction between 25 g and 29 g a day
    Certainty: trials support the direction found in the cohorts
    Reynolds et al., The Lancet, 2019 · checked 2026-09-16 · we read the abstract
17. fib-r5-1 · Position of an expert body · position statement of a professional association, summarizing the basis of the Dietary Reference Intakes · n = not a study; a position paper
    Dietary Reference Intakes recommend consumption of 14 g dietary fiber per 1,000 kcal, or 25 g for adult women and 38 g for adult men, based on epidemiologic studies showing protection against cardiovascular disease...The Dietary Reference Intakes for fiber are based on recommended energy intake, not clinical fiber studies. Usual intake of dietary fiber in the United States is only 15 g/day.
    
    Who: healthy adults in the United States
    Effect: Dietary Reference Intake 14 g per 1,000 calories, that is 25 g a day for adult women and 38 g a day for adult men, against a usual United States intake of only 15 g a day
    Certainty: an association position, not an analysis; the paper states outright that the figure follows recommended energy intake and not clinical fiber studies, and that appropriate amounts for children, the critically ill and the very old are unknown
    Slavin, position of the American Dietetic Association, Journal of the American Dietetic Association, 2008 · checked 2026-09-17 · we read the abstract
18. fib-e1-03 · Observational data · systematic review without meta-analysis, comparing four galactomannan sources across randomized trials · n = 50 randomized controlled trials
    Our findings suggest that the metabolic effects of galactomannans are source-dependent, with fenugreek-based interventions appearing to have greater potential for improving glycemic outcomes, while guar gum may be more effective in improving lipid parameters.
    
    Who: healthy adults and patients with metabolic disorders in 50 randomized controlled trials: 27 guar gum, 20 fenugreek, 2 mixed galactomannan, 1 locust bean gum
    Effect: fenugreek preparations consistently improved glycemic outcomes; guar gum showed more consistent effects on lipids; no clear dose-response relationship for fasting glucose, with reductions from near 0% to over 31.2%
    Certainty: the review reports no pooled estimate and the authors name considerable heterogeneity in participants, doses and duration; locust bean gum rests on a single trial, so the four-way comparison is not balanced
    Nutrients, 2026 · checked 2026-09-18 · we read the abstract
19. ev-fibc-10 · Position of an expert body · regulation · n = —
    Esophageal obstruction and asphyxiation due to orally-administered drug products containing water-soluble gums, hydrophilic gums, and hydrophilic mucilloids as active ingredients are significant health risks when these products are taken without adequate fluid or when they are used by individuals with esophageal narrowing or dysfunction, or with difficulty in swallowing.
    
    Who: users of OTC drug products with water-soluble or hydrophilic gums and mucilloids, including psyllium, methylcellulose, guar gum and glucomannan, in dry form
    Effect: label must warn of choking and tell users to take the product with at least 8 ounces of fluid; not for people with difficulty swallowing
    Certainty: applies to OTC laxative products, not to fiber in ordinary food
    21 CFR 201.319, Water-soluble gums, hydrophilic gums, and hydrophilic mucilloids (US FDA, eCFR current) · checked 2026-10-06 · we read the section