Beta-Glucans Explained: What They Are and Why They're Measured

Beta glucan is a type of dietary fibre made from chains of glucose, found in the cell walls of oats, barley, yeast and mushrooms. It is also one of the most quoted numbers on a mushroom supplement label.

This guide covers where beta-glucans come from, how their structure differs by source, how laboratories measure them, and why some figures look far higher than they should.

It ends with a simple way to read a beta-glucan result on a certificate of analysis, wherever you shop.

What Is Beta Glucan?

Beta glucan is a polysaccharide, a long chain of glucose units joined by beta linkages, that forms part of the cell wall in certain grains, yeasts, fungi and algae. The "beta" refers to the way the glucose units bond together, which is different from the "alpha" bonds found in starch.

That small chemical difference has a big practical effect. Human digestive enzymes break alpha bonds easily, which is why starch turns into glucose during digestion. Beta bonds are not broken down in the same way, so beta-glucans behave as dietary fibre rather than as a digestible carbohydrate.

Beta-glucans are not one single compound. The term covers a family of molecules that differ in chain length, branching and solubility depending on the source. A beta-glucan from oats is not structurally the same as a beta-glucan from yeast or mushrooms, and researchers study them separately for that reason.

Where Do Beta-Glucans Come From?

The main sources of beta-glucans are cereal grains (oats and barley), yeast, and mushrooms, with smaller amounts in some seaweeds and algae. Each source supplies a slightly different molecule.

The cereal figures above come from a review of beta-glucan as a soluble fibre, which also describes the structural split between cereal and fungal beta-glucans.

Oat and Barley Beta-Glucan

Oat and barley beta-glucans are the best documented. In the United States, the FDA permits a heart health claim for foods providing beta-glucan soluble fibre from whole oats or barley, based on 3 g per day under 21 CFR 101.81. That claim applies to oats and barley only, not to mushroom or yeast beta-glucans.

Mushroom and Yeast Beta-Glucan

Mushroom and yeast beta-glucans share a 1,3 backbone with 1,6 branches. They are often researched for their interaction with the immune system and gut, but that research is still developing and does not support disease claims for any supplement.

The 1,3/1,6 Structure Explained

The numbers in "1,3/1,6" describe which carbon atoms link one glucose unit to the next, and they are the clearest way to tell fungal beta-glucans apart from cereal ones.

Think of each glucose unit as a bead with numbered connection points. In a 1,3 linkage, carbon 1 of one bead joins carbon 3 of the next, forming the main chain. In a 1,6 linkage, a side branch sprouts from carbon 6. Mushrooms and yeast build long 1,3 chains with 1,6 branches coming off them, which gives a branched, more three dimensional shape.

Oats and barley do something different. Their chains mix 1,3 and 1,4 linkages along a mostly unbranched line. That is why oat beta-glucan dissolves readily and thickens liquids, the property behind its cholesterol research, while many fungal beta-glucans are less soluble and are usually concentrated by hot water extraction.

For a Lion's Mane product, this explains why extraction method matters. Hot water extraction is the traditional way to pull 1,3/1,6 beta-glucans out of the tough fungal cell wall, which contains chitin. A dual hot water and ethanol extraction, as Xotic uses, also captures alcohol soluble compounds alongside the polysaccharides.

How Are Beta-Glucans Measured?

Beta-glucans are usually measured by breaking all glucans down to glucose, measuring the alpha-glucans (mainly starch) separately, and calculating beta-glucan as the difference. This is the principle behind the most widely used mushroom and yeast method.

The best known test is the Megazyme yeast and mushroom beta-glucan assay (K-YBGL), based on work published by McCleary and Draga in the Journal of AOAC International in 2016. In simple terms, it works in three steps:

• Total glucan: the sample is hydrolysed with sulphuric acid to release glucose from every glucan present, and that glucose is measured.
• Alpha-glucan: a separate portion is treated with enzymes that break down starch and glycogen, and the free glucose (plus glucose from sucrose) is measured.
• Beta-glucan: the alpha-glucan figure is subtracted from total glucan, leaving the beta-glucan content.

Megazyme notes the kit is designed for mushroom, yeast and algae preparations that may also contain starch, maltodextrins, glycogen, sucrose and trehalose. That is exactly the point: the method is built to separate real beta-glucan from the other carbohydrates that often sit alongside it.

Oat and barley beta-glucans use different, cereal specific methods, so always check that the lab used a method suited to the source material.

Why Starch Inflates Total Polysaccharide Figures

A "total polysaccharides" figure counts every long sugar chain in a sample, including starch, so it can look high even when the beta-glucan content is low. This is the most common source of confusion on mushroom labels.

Older or cheaper tests, such as some colourimetric polysaccharide methods, react with almost any carbohydrate polymer. They do not distinguish beta-glucan from alpha-glucan. If a product contains starch, whether from grain the mushroom was grown on or from an added carrier such as maltodextrin, that starch is counted in the polysaccharide total.

This matters most with mycelium products grown on grain. Mycelium is often cultivated on rice or oats, and the finished powder can include a large share of the grain substrate. A polysaccharide test will read that starch as a positive result, while a beta-glucan test that subtracts alpha-glucans will not. The fruiting body vs mycelium comparison covers this difference in more detail.

When both figures are given, a large gap between them usually points to starch or other non beta-glucan carbohydrates.

How to Read a Beta-Glucan Figure on a COA

To read a beta-glucan result on a certificate of analysis, check the analyte name, the test method, the lab, the sample identity and the date, not just the percentage. A COA is only as useful as the details behind the number.

• Analyte: look for "beta-glucan" or "β-glucan" specifically, not "polysaccharides".
• Method: an enzymatic method that subtracts alpha-glucan, such as the Megazyme mushroom and yeast assay, is the reference point for fungal products.
• Alpha-glucan: if reported, a low alpha-glucan figure suggests little starch.
• Laboratory: the testing lab should be named and independent of the brand.
• Sample identity: the product or batch tested should match what you are buying.
• Date: recent results are more relevant than very old ones.

As an example, Xotic's published lab results include a 32.2% beta-glucan result on a tested extract powder blend containing 1% BioPerine (Symbio report S2162602 [R01], dated 13 May 2026). That is a sample-specific result, not a guarantee for every product or batch, and it is presented that way on purpose.

Xotic also lists AEGIC testing (November 2024) covering beta-glucans, heavy metals and nutrition on a submitted sample, and RMIT University testing (April 2025) in which E. coli and coliforms were not detected. A step by step walkthrough of reading a Lion's Mane COA covers the remaining lines, such as heavy metals and microbiology.

What Are Beta-Glucans Studied For?

Beta-glucans are studied for their role as dietary fibre and for how they interact with the gut and immune system, with the strongest evidence for oat and barley beta-glucan and cholesterol.

Oat and barley beta-glucan has an approved health claim in the US for heart health at 3 g per day, as noted above, and an equivalent cholesterol claim exists in the European Union. These are facts about cereal beta-glucan in food, not about mushroom supplements.

Mushroom beta-glucans are often researched for immune and gut related effects in laboratory and early human studies. Lion's Mane in particular is commonly associated with cognitive wellness research, although much of that work involves other compounds alongside beta-glucans. None of this supports claims that a supplement treats, cures or prevents any condition.

The responsible way to treat a beta-glucan percentage is as a quality and consistency marker. It shows that an extract is concentrated and made from real mushroom material, rather than promising a particular result.

Using Beta-Glucan Figures When You Buy Lion's Mane

Use the beta-glucan figure to compare extracts fairly: same analyte, same type of method, and a clear statement of what was tested.

Our Lion's Mane extract powder is 100% Lion's Mane fruiting body extract, with no added starch, grain, mycelium or fillers. It is grown in Thomastown, Victoria, Australia on Tasmanian oak hardwood sawdust and Australian soya husk, then harvested, freeze dried and processed into a 10:1 extract using hot water and ethanol dual extraction. It is vegan, gluten free and non GMO, and the powder and capsules ship internationally.

The label serve is 1 g of powder, or 2 x 300 mg Lion's Mane capsules, which contain the same extract. The powder works out cheaper per serve.

Specifying Beta-Glucans for Your Brand?

For brands, a beta-glucan figure becomes part of the product specification, so method, sample and documentation need to be agreed up front.

Ask any supplier for the beta-glucan method used, the alpha-glucan result, recent COAs, heavy metals and microbiological testing, and a sample before committing. Clarify MOQ and lead times early, especially if your formula includes other ingredients.

Xotic supplies white and private label Lion's Mane plus bulk extract in 1 kg and 5 kg formats. White label places our established powder or capsules under your brand. Private label covers your own blend, formulation or packaging, usually with higher MOQs and longer lead times.

Beta Glucan in Summary

Beta glucan is a fibre found in oats, barley, yeast and mushrooms, and the way it is measured matters as much as the number.

Shop for Lion's Mane extract powder or capsules with published testing, and look for beta-glucans, not polysaccharides. Brands can ask about white label, private label or bulk supply.

FAQs

1. What is beta glucan?

Beta glucan is a type of dietary fibre made from chains of glucose joined by beta linkages. It forms part of the cell walls of oats, barley, yeast and mushrooms. Because human enzymes do not break beta bonds the way they break the alpha bonds in starch, beta-glucans behave as fibre rather than as a digestible carbohydrate.

2. What foods are highest in beta-glucans?

Oats and barley are the richest everyday food sources, with oats containing roughly 6 to 8% beta-glucan and barley about 4 to 10% depending on variety. Mushrooms such as shiitake, oyster and Lion's Mane, and baker's yeast, also contain beta-glucans, and extraction can concentrate them in mushroom supplements.

3. What is the difference between oat and mushroom beta-glucan?

Oat beta-glucan has a mixed 1,3 and 1,4 linkage structure and is highly soluble, which is why it thickens liquids. Mushroom beta-glucan has a 1,3 backbone with short 1,6 branches and is often less soluble. They are studied separately, and the US oat and barley heart health claim does not apply to mushroom beta-glucans.

4. How is beta-glucan measured in mushrooms?

The most common approach is an enzymatic method such as the Megazyme yeast and mushroom assay. The lab measures total glucan, separately measures alpha-glucans such as starch, and calculates beta-glucan as the difference. This removes starch from the result, which is why it is more reliable than a total polysaccharide test for mushroom products.

5. Why are polysaccharide figures higher than beta-glucan figures?

Total polysaccharide tests count every carbohydrate polymer in a sample, including starch from grain substrates or added carriers such as maltodextrin. A beta-glucan test subtracts those alpha-glucans. So a product can show a high polysaccharide percentage while its true beta-glucan content is much lower, especially for mycelium grown on grain.

6. What should I look for in a beta-glucan result on a COA?

Check that the analyte is beta-glucan rather than polysaccharides, that the method subtracts alpha-glucans, and that an independent laboratory is named. Confirm the sample or batch matches the product, and look at the test date. Treat any single result as specific to that sample rather than a guarantee for every batch.

7. Are beta-glucan supplements safe?

Beta-glucans from oats, barley, yeast and mushrooms are widely eaten as part of normal foods. As with any supplement, follow the label serve, and speak with a doctor before use if you have a health condition, take medication, or are pregnant or breastfeeding. Mild digestive changes can occur with higher fibre intakes.