Pick up two tubs of mushroom supplement and you will often find two entirely different kinds of number on the back. One says “standardised to 30% polysaccharides”. Another says “40% beta-glucans”. A third says nothing at all, and simply lists species.

Most buyers reasonably assume the bigger number is the better product. Sometimes it is. Often it is not, and occasionally it is precisely backwards — because the two figures are not measuring the same thing, and one of them can be inflated by an ingredient that is not mushroom at all.

This is the most technical article we will write on this subject, and it is the one worth reading twice. Understand what these numbers mean and you will never be sold cereal grain again.

What is a beta-glucan?

Beta-glucans are a family of complex carbohydrates — polysaccharides — that make up much of the cell wall structure of fungi. They are the compounds functional mushrooms are studied for and, in the plainest terms, the reason anyone takes a mushroom supplement rather than eating a slice of bread.

They are found in the cell walls of the mushroom itself. Not in the soil it grew in, not in the sawdust or the grain, but in the fungal tissue. That single fact is the key to everything that follows.

When you buy a Mushroom Powder for Dogs, what you are paying for is fungal cell wall material and the compounds bound up in it. A high-quality product delivers a lot of it per scoop. A poor one delivers very little, wrapped in something cheap that weighs the same.

Why polysaccharide percentages can mislead

Here is the crux. Beta-glucans are polysaccharides — but not all polysaccharides are beta-glucans.

Starch is also a polysaccharide. So is the alpha-glucan found in cereal grains. A laboratory test that measures total polysaccharide content will count all of them together and return a single number, and that number cannot tell you which part came from mushroom and which came from rice.

This matters because of how a great deal of mushroom supplement is made. Mycelium — the root-like growth stage of a fungus — is commercially cultivated on sterilised cereal grain. When the block is dried and milled whole, the grain goes into the powder with it. A total-polysaccharide test will happily count that grain as though it were active ingredient.

The figures from independent analysis are stark. Myceliated-grain products have been found to average 35 to 40 per cent starch, against under 3 per cent in whole mushrooms. Beta-glucan content in those same grain-grown products typically lands between 1 and 10 per cent, where properly grown fruiting bodies test between 28 and 49 per cent.

So a product can advertise a healthy-looking polysaccharide percentage while most of that percentage is unconverted grain. The number is not fraudulent. It is simply answering a different question from the one the buyer thinks they asked.

The hierarchy of label claims

In practice, what you find on shelves falls into four tiers. It is worth knowing where a product sits before you judge its price.

Tier one — a stated beta-glucan percentage, from fruiting body extract, with a certificate of analysis available

This is the gold standard and it is rarer than it should be. The brand has commissioned a specific enzymatic assay that distinguishes beta-glucans from alpha-glucans, and will show you the result. If you find this, you are looking at a company that has spent money to find out what is in its own product.

Tier two — extract, with a stated standardisation, from a brand that will show its analysis on request

The word “extract” tells you the material has been concentrated rather than merely dried and ground. A stated standardisation — even if expressed as polysaccharides rather than beta-glucans — tells you the raw material has been tested against a specification rather than bought on trust. This is a solid, honest tier and covers many genuinely good products.

The way to test a tier-two product is simply to email and ask for the certificate of analysis. A brand at this level will send it. What comes back tells you whether it belongs in tier one.

Tier three — species listed, no extraction detail, no numbers

You cannot tell what you are buying. It may be dried whole mushroom, which is not worthless but is far less concentrated than extract. It may be milled substrate. The absence of any figure is itself informative: a company that had tested and liked the result would generally print it.

Tier four — “mycelium on grain”, “mycelial biomass”, “fermented on rice”, with a polysaccharide percentage quoted

This is the combination to walk away from. The wording tells you substrate is included; the polysaccharide figure is inflated by that substrate; and the two together suggest a product engineered to look impressive on a label rather than to work in a bowl.

How beta-glucan testing actually works

You do not need this to shop well, but it explains why good products cost more.

• Crude polysaccharide testing. The cheap approach. It measures everything that behaves like a polysaccharide and reports a total. Inexpensive, fast, and unable to distinguish mushroom from grain.
• Enzymatic assay. The proper approach. Specific enzymes are used to break down alpha-glucans separately from beta-glucans, so the two can be measured independently. It costs more per sample, which is precisely why fewer brands do it.

A brand quoting a beta-glucan figure has almost certainly paid for the second kind of test. That is the practical signal buried in the number.

What counts as a good number?

For a fruiting body extract, beta-glucan content in the twenties, thirties or forties as a percentage is the range associated with well-grown, properly extracted material. Single-digit beta-glucan figures on a product sold as a concentrated extract are a reason to ask questions.

For polysaccharide figures, treat them as a floor rather than a ceiling — evidence that a specification exists, not proof of potency. A stated 30 per cent polysaccharide standardisation on a genuine extract is a meaningfully different proposition from the same figure on a grain-grown mycelium product, because the starting material is different.

Which brings us to the only rule that really holds: the number is only as good as the material it describes. Establish what the material is first, then read the number.

Why does any of this exist?

Because growing real mushrooms is slow and growing mycelium on grain is not.

A fruiting body crop takes months, needs controlled conditions and space, and yields a limited harvest. A bag of sterilised grain can be inoculated and colonised in weeks, in far less space, with far less expertise. The resulting block weighs a great deal, mills easily, and can legally be described using the mushroom’s name.

None of this is illegal. “Mycelial biomass” is an accurate description of what is in the bag. There is simply no requirement anywhere to declare what proportion of that biomass is unconverted substrate, and so, for the most part, nobody does.

The four questions worth asking

Copy these into an email before you buy a second tub of anything.

• Which part of the mushroom is used? Fruiting body, mycelium, or mycelium grown on grain?
• Is it an extract? If yes, what ratio or standardisation, and against what specification?
• What is the beta-glucan content? If they can answer this, they have paid for proper testing.
• Will you send me the certificate of analysis? The answer to this question tells you more about a company than the other three combined.

Frequently asked questions

Is a higher percentage always better?

No — not unless you know what is being measured. A 40 per cent polysaccharide figure on a grain-grown product can represent less actual fungal material than a 30 per cent figure on a genuine extract. Establish the material first.

Are beta-glucans safe for dogs?

Beta-glucans are found in ordinary foods including oats, barley and baker’s yeast, and are a normal part of many diets. In cultivated functional mushrooms fed at sensible amounts, the safety record in dogs is good. Introduce gradually and follow the weight guide, and speak to your vet first if your dog is pregnant, nursing, on medication or under veterinary care.

Does cooking or extraction destroy them?

The opposite. Fungal cell walls are made largely of chitin, which dogs digest poorly. Hot water extraction is what breaks those walls down and makes the compounds inside available. It is the reason extract is a meaningfully different product from dried, milled mushroom.

Can I test a product myself?

Not practically. Laboratory assays are the only reliable method. What you can do is ask for the analysis — and treat reluctance as an answer in itself.

Does this apply to human mushroom supplements too?

Yes, in exactly the same way. The manufacturing shortcut and the labelling gap are identical across the human and pet markets.

The short version

Beta-glucans are the compounds that matter. Polysaccharide totals include them but also include starch, which means a polysaccharide figure can be inflated by cereal grain that was never mushroom at all.

Read the material before you read the number. Extract beats dried powder. Fruiting body beats mycelium grown on grain. A stated specification beats silence. And a brand willing to send you its certificate of analysis beats every marketing claim ever printed on a tub.

Six years in the pet supplement industry has taught us something simple about this category: the companies doing the work are happy to be asked specific questions, and the ones that are not will answer with heritage, tradition and a photograph of a forest.