Beta glucan is one of those supplements that sounds complicated but is actually found in everyday foods. If you eat oatmeal, you’re already getting some. The question is whether taking it as a supplement offers anything beyond what you’d get from a bowl of porridge.

I’ve gone through the clinical evidence to sort out what beta glucan might actually do from what’s mostly marketing.

What is beta glucan?

Beta glucan is a type of soluble fibre (a polysaccharide, technically) found in the cell walls of bacteria, fungi, yeast, and plants like barley and oats. The structure varies depending on the source, which matters because different structures have different effects in the body.

Oat and barley beta glucans have what’s called a (1,3/1,4) linkage pattern. These are the ones with the strongest evidence for cholesterol and blood sugar effects. Yeast and mushroom beta glucans, including those from reishi, have a (1,3/1,6) pattern with more side chain branching. The more branching, the more biologically active the compound tends to be for immune effects.

Common branded forms include Epicor (from yeast fermentation) and Wellmune (from baker’s yeast cell walls). These are the versions most often studied for immune function.

Benefits with reasonable evidence

1. Cholesterol reduction

This is where oat beta glucan has its strongest case. The European Food Safety Authority has actually approved a health claim for it, stating that 3 grams daily of oat beta glucan can reduce LDL cholesterol [1].

A 2020 meta-analysis of 21 randomised controlled trials involving 1120 people with mild hypercholesterolaemia found that taking at least 3 grams of beta glucan daily for a minimum of three weeks reduced total cholesterol by 0.27 mmol/L and LDL cholesterol by 0.26 mmol/L compared to controls [2].

These aren’t dramatic numbers. For context, statins typically reduce LDL by 1-2 mmol/L. But for people with borderline cholesterol who want to try dietary changes before medication, it’s something. The same analysis found that combining solid foods (like oat bran) with liquid products (like oat drinks) seemed to work better than either alone.

My take: if you have mildly elevated cholesterol and are looking for dietary approaches alongside lifestyle changes, oat beta glucan is worth considering. Don’t expect it to replace medication for significant dyslipidaemia.

2. Blood sugar control

For people with type 2 diabetes, oat beta glucan may help smooth out blood sugar spikes. A 2016 meta-analysis of 4 randomised trials with 350 diabetic participants found that 2.5 to 3.5 grams daily for 3-8 weeks reduced both fasting glucose and HbA1c (the long-term blood sugar marker) [3].

The mechanism is fairly well understood: beta glucan forms a gel in the gut that slows carbohydrate absorption. It’s the same reason why eating whole oats leaves you feeling full longer than eating refined grains.

The catch is that 350 participants across 4 studies is a small evidence base. The effects were statistically significant but modest. I wouldn’t rely on beta glucan alone for diabetes management, but it could be a reasonable addition to existing treatment.

3. Upper respiratory tract infections

This is where yeast-derived beta glucan (rather than oat) gets interesting. A 2021 systematic review and meta-analysis of 13 randomised controlled trials found that yeast beta glucan reduced the incidence of upper respiratory infections, shortened their duration, and improved symptom severity compared to placebo [4].

Upper respiratory infections include the common cold, sinusitis, pharyngitis, and similar viral illnesses. They’re the main reason people misuse antibiotics (which don’t work against viruses), so anything that reduces their frequency could have broader benefits.

The evidence here is actually reasonably consistent across studies. Yeast beta glucan appears to stimulate certain immune cells, particularly macrophages and natural killer cells, though the exact mechanism is still being worked out.

The limitation: many of these studies were funded by companies making beta glucan products. That doesn’t mean the results are wrong, but it’s worth keeping in mind.

Benefits with weaker evidence

4. Weight loss

A 2019 meta-analysis of 12 randomised trials found that beta glucan supplements reduced body weight and BMI compared to controls [5]. However, the effect sizes were small, and the researchers noted that taking more than 4 grams daily actually increased total energy intake in some studies.

I’m sceptical here. The weight effects could simply be from increased satiety (feeling full longer) due to the fibre, which you could also get from eating more whole grains. There’s nothing magic about taking it as a supplement for this purpose.

5. Cancer therapy support

This is the most tentative area. A 2020 systematic review of 16 clinical trials involving 1650 cancer patients suggested that beta glucan given alongside chemotherapy or radiation therapy might reduce treatment-induced immunosuppression and help white blood cell counts recover faster [6].

However, the same review noted that some studies found no difference between beta glucan and control groups. The quality of evidence was low overall.

I would not recommend beta glucan as part of cancer treatment without discussing it with an oncologist first. The potential for interaction with immunosuppressive therapies (more on this below) makes this a situation where self-treatment could cause problems.

Side effects

Oral beta glucan is generally well tolerated. The most common side effects are gastrointestinal:

Diarrhoea
Nausea
Vomiting
Bloating (particularly at higher doses)

These are typical of soluble fibre supplements and usually improve once your gut adjusts.

Intravenous beta glucan (used in some clinical trials and hospital settings) has a longer list of potential effects including fever, chills, injection site pain, headache, joint pain, fatigue, and changes in blood pressure. This form isn’t available as a consumer supplement.

Safety precautions (5 contraindications)

1. Pregnancy and breastfeeding

The safety of beta glucan supplements during pregnancy and breastfeeding hasn’t been established. Eating oats is fine, but concentrated supplements are a different matter. I’d avoid them unless there’s a specific medical reason and your doctor approves.

2. Autoimmune conditions

Some forms of beta glucan stimulate the immune system. For most people this is either neutral or potentially beneficial, but if you have an autoimmune condition where your immune system is already overactive, this could theoretically make things worse.

This is particularly relevant for conditions like lupus, rheumatoid arthritis, multiple sclerosis, or interstitial cystitis (which has autoimmune features in some patients). Talk to your doctor first.

3. Immunosuppressant medications

If you’re taking medications that suppress your immune system, beta glucan could work against them. This includes drugs like:

Azathioprine (Imuran)
Ciclosporin
Tacrolimus
Mycophenolate
Prednisone and other corticosteroids
Biologics like basiliximab or daclizumab

People who have had organ transplants or are being treated for autoimmune diseases often take these medications. Beta glucan’s immune-stimulating effects could interfere with how well they work [7].

4. Diabetes medications

Beta glucan can lower blood sugar. If you’re already taking insulin or oral hypoglycaemic drugs like metformin or sulphonylureas, adding beta glucan could increase your risk of hypoglycaemia (low blood sugar). This isn’t necessarily a reason to avoid it, but you should monitor your blood sugar more closely and discuss the combination with your doctor.

5. Blood pressure medications

There’s some evidence that beta glucan may lower blood pressure slightly. If you’re already on antihypertensive medication, the combined effect could potentially cause your blood pressure to drop too low. Again, this is about monitoring and communication with your healthcare provider rather than absolute avoidance.

A note on an unusual side effect

In patients with AIDS or AIDS-related syndromes, intravenous beta glucan has caused keratoderma (thickening of the skin on the palms and soles). This appeared within two weeks of treatment and resolved 2-4 weeks after stopping [8]. This is specific to the injectable form and immune-compromised patients, but worth noting.

How much to take

For cholesterol: 3 grams daily of oat beta glucan (the EFSA-approved dose)

For blood sugar: 2.5-3.5 grams daily

For immune support: doses in studies range from 250 mg to 500 mg daily for yeast beta glucan (Wellmune or similar)

The source matters. Oat beta glucan from food or supplements is better studied for metabolic effects. Yeast beta glucan is better studied for immune effects.

The bottom line

Beta glucan isn’t a miracle supplement, but it’s not worthless either. The cholesterol-lowering effects of oat beta glucan are well-established enough that European regulators allow health claims. The blood sugar and immune benefits are promising but based on smaller evidence bases.

For most people, eating more oats and other whole grains would be a sensible first step. If you want to try supplements, stick to reputable brands with defined beta glucan content, and keep your expectations realistic.

If you’re interested in other supplements that may support immune function, you might also want to read about vitamin C, zinc, or probiotics. For cholesterol management, see also fish oil and red yeast rice.

References

EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on the substantiation of a health claim related to oat beta-glucan and lowering blood cholesterol. EFSA Journal. 2010;8(12):1885.
Ho HV, Sievenpiper JL, Zurbau A, et al. A systematic review and meta-analysis of randomized controlled trials of the effect of barley β-glucan on LDL-C, non-HDL-C and apoB for cardiovascular disease risk reduction. Eur J Clin Nutr. 2016;70(11):1239-1245. doi:10.1038/ejcn.2016.89
Shen XL, Zhao T, Zhou Y, Shi X, Zou Y, Zhao G. Effect of oat β-glucan intake on glycaemic control and insulin sensitivity of diabetic patients: a meta-analysis of randomized controlled trials. Nutrients. 2016;8(1):39. doi:10.3390/nu8010039
Zheng B, et al. Yeast β-glucan supplementation and upper respiratory tract infection prevention: A meta-analysis of randomised controlled trials. PLoS One. 2021;16(5):e0251710. doi:10.1371/journal.pone.0251710
Aoe S, Ichinose Y, Kohyama N, et al. Effects of high β-glucan barley on visceral fat obesity in Japanese individuals: A randomized, double-blind study. Nutrition. 2017;42:1-6. doi:10.1016/j.nut.2017.05.002
Bashir KMI, Choi JS. Clinical and physiological perspectives of β-glucans: The past, present, and future. Int J Mol Sci. 2017;18(9):1906. doi:10.3390/ijms18091906
National Institutes of Health. Beta-glucans. MedlinePlus. Available at: https://medlineplus.gov/druginfo/natural/1041.html
Petersen KS, Rushing JT, Guilkey S, et al. Keratoderma related to intravenous glucan therapy in AIDS patients. J Am Acad Dermatol. 1989;20(5 Pt 2):941-944. doi:10.1016/s0190-9622(89)70116-4