What Are Beta-Glucans?

Beta-glucans are among the most talked-about compounds in mushrooms, and among the most misunderstood. They appear on labels, in marketing and throughout research papers. This article explains what they actually are, where they come from, how their structure varies and why the details matter.

What are beta-glucans?

Beta-glucans are polysaccharides: long chains of glucose molecules. Glucose can be linked together in different ways. When the links are of a type chemists call “beta” linkages, the result is a beta-glucan. When they are “alpha” linkages, the result is something quite different, such as starch.

Beta-glucans also vary in how their chains are connected and branched, which is described with numbers such as 1,3 or 1,6. These structural details differ between sources.

Where are they found?

• Mushrooms and other fungi, where they form part of the cell wall, typically with a 1,3 backbone and 1,6 branches.
• Yeasts, such as baker’s yeast.
• Cereals, particularly oats and barley, where the structure is different (mixed 1,3 and 1,4 linkages).

This matters because beta-glucans from different sources are not interchangeable. For example, there are authorised health claims in the UK for beta-glucans from oats and barley, but these relate specifically to cereal beta-glucans and don’t apply to beta-glucans from mushrooms.

Where are they in a mushroom?

In mushrooms, beta-glucans are built into the cell wall alongside chitin, the tough material also found in insect shells. That structure is part of why mushrooms are hard to digest raw and why extraction matters. Hot water is the traditional and most effective way of drawing beta-glucans out, which is why they are the main target of the hot water stage of a dual extract. Alcohol, by contrast, makes them come out of solution. See Chitin and the Fungal Cell Wall.

Structure in more detail

Fungal beta-glucans typically have a backbone of glucose units linked in the β-1,3 position, with side branches attached at the β-1,6 position. Beyond that, they vary in:

• Branching: how often side chains occur.
• Molecular size: from relatively small to very large molecules.
• Shape in solution: some form triple helices; others don’t.
• Attachments: some are bound to protein.

Why structure matters

Researchers have found that these structural features affect how beta-glucans dissolve and how they behave in laboratory systems. As a result, beta-glucans from different species, or from the same species prepared differently, can’t be assumed to be equivalent. “Beta-glucans” isn’t one substance.

Named mushroom beta-glucans

Some well-characterised mushroom beta-glucans have their own names, such as lentinan from shiitake, schizophyllan from split gill fungus and pleuran from Oyster mushroom. These are specific, purified preparations, and studies on them don’t describe whole mushroom extracts.

Beta-glucans, alpha-glucans and starch

Because both are glucose chains, beta-glucans are easy to confuse with alpha-glucans, including starch. This becomes important when products are tested. A test that measures total polysaccharides or total glucans without separating the two can include starch from grain, making a product made from mycelium on grain appear richer in “glucans” than it really is in fungal beta-glucans.

Our articles Beta-Glucan Testing Explained and Fruiting Body vs Mycelium go into this further.

What does the research say?

What this means when choosing a product

• Beta-glucans are a natural part of mushrooms, not an added ingredient.
• Extraction, especially hot water extraction, affects how much reaches the finished product.
• Figures on labels are only meaningful if you know how they were measured.
• Grain-grown mycelium can distort glucan figures through its starch content.

How we approach it

Our tinctures are made from UK-grown fruiting bodies, and wild Finnish chaga, extracted in hot water with the help of ultrasonic extraction and in plant-derived ethanol. We don’t quote beta-glucan figures on our products unless they are supported by testing of that product.