Oat and barley beta-glucan

What it is

Beta-glucan is a viscous, soluble fibre found in oats and barley. It is the component thought to explain oats' cholesterol-lowering effect.

What the research says

Beta-glucan lowers LDL cholesterol. A 58-trial meta-analysis found a median 3.5 g a day lowered LDL by 0.19 mmol/L. Another analysis found about 0.25 mmol/L at 3 g a day or more, with no change in HDL cholesterol or triglycerides. Trials show large unexplained differences between studies, and many did not measure how much beta-glucan their test foods actually contained. Gut side effects such as flatulence occur with fibres like this one.

Evidence grade: Well established.

What goes wrong

In a PepsiCo-funded 4-week trial of 3 g/day oat beta-glucan, gut symptoms such as flatulence and abdominal discomfort rose on both the beta-glucan and control drinks, then began to settle. (Source 1)

• Randomized trial, Low certainty.
• Size: 207 randomised (191 analysed)
• Who: Adults with borderline high LDL cholesterol.
• How long: 4 weeks.
• Result: Any major GI symptom: 36% vs 28% at baseline, 61% vs 52% at week 2, 47% vs 42% at week 4 (beta-glucan vs control)
• Funding: Industry-funded (PepsiCo)

One or more major GI symptom (flatulence, diarrhea, constipation, abdominal distention, and abdominal pain) was present in 36% of Test and 28% of Control participants at baseline (ns); the prevalence increased to 61% and 52%, respectively, at week 2 and fell to 47% and 42% by week 4.

The same trial authors note that dietary fibres commonly cause bloating, pain, wind and diarrhoea, which are usually temporary. (Source 2)

• Randomized trial, Low certainty.
• Size: 207 randomised.
• Who: Adults with borderline high LDL cholesterol.
• How long: 4 weeks.
• Result: Background statement on fibre side effects.
• Funding: Industry-funded (PepsiCo)

The undesirable side-effects of dietary fibers include abdominal bloating and pain, flatus and diarrhea which, although transitory in nature, may limit the acceptability of high fiber foods.

What the evidence supports

In a meta-analysis of 58 randomised trials, a median 3.5 g/day of oat beta-glucan lowered LDL cholesterol, non-HDL cholesterol and apoB compared with control. (Source 3)

• Meta-analysis, Moderate certainty.
• Size: 3974 participants across 58 trials.
• Who: Adults, including people who were overweight or had high cholesterol.
• How long: 3 weeks or more.
• Result: LDL -0.19 mmol/l (95% CI -0.23 to -0.14); non-HDL -0.20 mmol/l; apoB -0.03 g/l; I2 = 79% for LDL.
• Funding: Some authors declared industry research support, consulting, patents on viscous fibre blends, and ownership of a testing laboratory.

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)

In 28 trials of 3 g/day or more of oat beta-glucan, LDL fell by 0.25 mmol/L and total cholesterol by 0.30 mmol/L. (Source 4)

• Meta-analysis, Moderate certainty.
• Size: 28 RCTs.
• Who: Adults, with and without high cholesterol or diabetes.
• How long: 2-12 weeks.
• Result: LDL -0.25 mmol/L (95% CI 0.20-0.30; P<0.0001); total cholesterol -0.30 mmol/L (95% CI 0.24-0.35)
• Funding: Not stated in the abstract we read.

OBG in doses of ≥3 g/d reduced low-density lipoprotein (LDL) and total cholesterol relative to control by 0.25 mmol/L (95% CI: 0.20, 0.30; P < 0.0001)

Position (US FDA, current regulation): foods may carry a heart-disease health claim for beta-glucan soluble fibre from whole oats or barley at 3 g or more per day. (Source 5)

• Official position, Certainty not rated.
• Size: Not applicable.
• Who: US food labelling.
• How long: Not applicable.
• Result: Qualifying intake level set in 21 CFR 101.81.
• Funding: Government.

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.

What the evidence does not support

Oat beta-glucan had no significant effect on HDL cholesterol or triglycerides, and neither dose nor duration changed the results. (Source 4)

• Meta-analysis, Moderate certainty.
• Size: 28 RCTs.
• Who: Adults.
• How long: 2-12 weeks.
• Result: No significant HDL or triglyceride change; no dose-response across 3.0-12.4 g/d.
• Funding: Not stated in the abstract we read.

There was no significant effect of OBG on high-density lipoprotein (HDL) cholesterol or triglycerides and no evidence that dose (range across trials: 3.0-12.4 g/d) or duration of treatment (range: 2-12 wk) influenced the results.

Where the evidence is mixed

The same review reported considerable unexplained heterogeneity between trials in its LDL and non-HDL cholesterol results. (Source 3)

• Meta-analysis, Moderate certainty.
• Size: 58 trials.
• Who: As above.
• How long: As above.
• Result: I² = 79% for LDL cholesterol, 99% for non-HDL cholesterol.
• Funding: As above.

There was evidence for considerable unexplained heterogeneity in the analysis of LDL-cholesterol (I 2=79 %) and non-HDL-cholesterol (I 2=99 %).

The authors also noted that for most trials the beta-glucan content of the oats was estimated rather than measured, which makes the size of the effect hard to pin down. (Source 6)

• Meta-analysis, Moderate certainty.
• Size: 58 trials.
• Who: As above.
• How long: As above.
• Result: Limitation stated by the authors.
• Funding: As above.

The first one being that the β-glucan content of oats was estimated for the majority of trials as it was not routinely analysed and reported.

How much

• Reference intake: No RDA or AI exists for beta-glucan itself. The US FDA health-claim regulation (21 CFR 101.81, current eCFR) names 3 g or more per day of beta-glucan from whole oats or barley as the intake linked to reduced heart disease risk for labelling purposes. (Source 5)
• Upper limit: We found no tolerable upper intake level for beta-glucan in the sources we read. (Source 4)
• Studied: Trials in the Ho meta-analysis gave a median 3.5 g/day of oat beta-glucan for at least 3 weeks. (Source 3)
• Studied: Trials in the Whitehead meta-analysis gave 3.0 to 12.4 g/day for 2 to 12 weeks. (Source 4)
• Studied: The Wolever trial gave a drink containing 1 g of beta-glucan three times daily for 4 weeks. (Source 7)

A common belief, and what the research shows

The belief: Oat beta-glucan improves the whole cholesterol profile, including 'good' HDL and triglycerides.

What the research shows: The benefit is to LDL and total cholesterol. A 28-trial meta-analysis found "no significant effect of OBG on high-density lipoprotein (HDL) cholesterol or triglycerides".

Questions and answers

What is it?

Beta-glucan is a viscous, soluble fibre found in oats and barley. (Source 8)

What does it do in the body?

Trials show it lowers LDL cholesterol, non-HDL cholesterol and apoB. It does not change HDL cholesterol or triglycerides. (Source 3)

Is it good or bad for you?

The evidence supports a modest LDL-lowering benefit. The main downside reported is temporary gut symptoms such as flatulence, which in one trial also rose on the control drink. (Source 9)

How do you get more of it?

Trials added oat beta-glucan to the diet at 3 g a day or more, through foods or drinks. This describes what was studied and is not a recommendation. (Source 4)

If it is harmful, what reduces it?

Does not apply. Beta-glucan is not harmful in the amounts studied. The side effects reported were temporary gut symptoms. (Source 2)

Why might someone be low in it or missing it?

Beta-glucan is not an essential nutrient, so there is no deficiency. Intake is low when the diet contains few oats or barley. The FDA regulation notes that populations with low heart disease rates tend to eat more fibre-containing grain products such as whole oats. (Source 10)

Which whole foods contain it or feed it?

Whole oats and barley. How much beta-glucan they contain varies with the plant variety and growing conditions. (Source 6)

What happens if you do not have it?

No deficiency disease is described. Without beta-glucan, people miss out on the modest LDL-lowering effect seen in trials. (Source 3)

How can you test for it?

No test measures beta-glucan status in the body. Its effect is judged indirectly by measuring blood LDL cholesterol, as the trials did. (Source 8)

We searched: Looked for any biomarker of beta-glucan intake or status in the meta-analyses by Ho 2016 and Whitehead 2014 and in the Wolever 2021 trial; none was described. Outcomes were blood lipids.

References

1. Nutrients. Effect of Oat β-Glucan on Affective and Physical Feeling States in Healthy Adults: Evidence for Reduced Headache, Fatigue, Anxiety and Limb/Joint Pains. 2021. DOI 10.3390/nu13051534. Read the source
2. Nutrients. Effect of Oat β-Glucan on Affective and Physical Feeling States in Healthy Adults: Evidence for Reduced Headache, Fatigue, Anxiety and Limb/Joint Pains. 2021. DOI 10.3390/nu13051534. Read the source
3. British Journal of Nutrition. The effect of oat β-glucan on LDL-cholesterol, non-HDL-cholesterol and apoB for CVD risk reduction: a systematic review and meta-analysis of randomised-controlled trials. 2016. DOI 10.1017/S000711451600341X. Read the source
4. American Journal of Clinical Nutrition, via NCBI Bookshelf (Database of Abstracts of Reviews of Effects). Cholesterol-lowering effects of oat β-glucan: a meta-analysis of randomized controlled trials (DARE structured abstract). 2014. PMID 25411276. Read the source
5. US Food and Drug Administration (Electronic Code of Federal Regulations). 21 CFR 101.81 Health claims: Soluble fiber from certain foods and risk of coronary heart disease (CHD), paragraph (c)(2)(i)(G). current as of 2026. Read the source
6. British Journal of Nutrition. The effect of oat β-glucan on LDL-cholesterol, non-HDL-cholesterol and apoB for CVD risk reduction: a systematic review and meta-analysis of randomised-controlled trials. 2016. DOI 10.1017/S000711451600341X. Read the source
7. Nutrients. Effect of Oat β-Glucan on Affective and Physical Feeling States in Healthy Adults: Evidence for Reduced Headache, Fatigue, Anxiety and Limb/Joint Pains. 2021. DOI 10.3390/nu13051534. Read the source
8. British Journal of Nutrition. The effect of oat β-glucan on LDL-cholesterol, non-HDL-cholesterol and apoB for CVD risk reduction: a systematic review and meta-analysis of randomised-controlled trials. 2016. DOI 10.1017/S000711451600341X. Read the source
9. Nutrients. Effect of Oat β-Glucan on Affective and Physical Feeling States in Healthy Adults: Evidence for Reduced Headache, Fatigue, Anxiety and Limb/Joint Pains. 2021. DOI 10.3390/nu13051534. Read the source
10. US Food and Drug Administration (Electronic Code of Federal Regulations). 21 CFR 101.81 Health claims: Soluble fiber from certain foods and risk of coronary heart disease (CHD), paragraph (a)(2). current as of 2026. Read the source