Fruiting Body vs Mycelium: What's the Difference in Your Mushroom Coffee?

The fruiting body is the mushroom itself; mycelium is the thread-like network it grows from. In most mushroom coffees the distinction matters less for biology than for what else is in the tub: mycelium is usually grown on cereal grain and sold with that grain still in it, and lab tests of those products have found roughly a quarter to two-thirds starch. Mycelium isn’t a fake ingredient, but a label that says “mushroom” without saying which part, or what it grew on, leaves out the thing you most need to know.

This page is about what’s in the powder, not about what mushrooms do for you. We make no health claims here, and the evidence section below says why.

How is mycelium on grain made?

Mushroom growers have done this for nearly a century, for a different reason. To start a crop, mycelium is “propagated on a base of steam-sterilized cereal grain (usually rye or millet)”, and that grain-and-mycelium mix is called spawn (Penn State Extension; Penn State Spawn Lab). On a farm, spawn is the seed. Many supplement makers stop at this stage instead: they dry the colonized grain, mill it and sell it.

Why does the grain stay in?

Because the threads grow through and around each kernel, and there’s no practical way to pull them apart. A guest post by the co-founder of a mushroom farm puts it plainly: at harvest, “separating them is not practically possible”, so the grain goes into the powder (Vegconomist; the author grows mushrooms commercially).

How much of the grain is left? A 2025 peer-reviewed study tested four commercial “fermented grain” chaga products alongside plain cooked oats, rice and sorghum. The grain products were 33% to 68% alpha-glucan (starch), the plain grains 46% to 74%, and the authors concluded that fermentation “does not substantially alter the chemical profile of the grain substrate” (Windsor et al., 2025). Five of its six authors work for Nammex, which sells fruiting-body extracts, so this is careful work from an interested party, on four products.

Starch vs beta-glucan: why the number on the label can mislead

Both are glucans, chains of glucose. The difference is the bond between the glucose units, and that changes what they are:

• Alpha-glucan is starch (in grain) or glycogen (the form fungi store glucose in).
• Beta-glucan is found in fungal cell walls, and it’s the compound most mushroom research measures.

The validated lab method measures total glucan, measures the alpha-glucan (starch and glycogen) separately, and reports beta-glucan as the difference (McCleary & Draga, 2016; the lead author founded Megazyme, which sells the test kit). A plain “total polysaccharides” test skips that subtraction, so starch from grain counts toward the number. That’s why “40% polysaccharides” on a grain-grown product can mean mostly oats.

Even a beta-glucan figure isn’t immune. Oats contain their own cereal beta-glucan, and the 2025 study attributes the beta-glucan it measured in an oat-grown product to “cereal β-glucans and cellulose” rather than to the fungus (Windsor et al., 2025). That’s why a starch figure next to the beta-glucan figure tells you more than either alone.

What the numbers look like in practice:

Sample	Beta-glucan	Alpha-glucan (starch)	Source
Fruiting-body products	25–66%	Not reported	Nammex presentation, 2016 (22 samples in all)
Mycelium-on-grain products	Under 10%	24–70%	Nammex presentation, 2016 (same set)
Whole chaga (6 samples)	5.7–11.9%	Under 2%	Windsor et al., 2025
Chaga mycelium grown without grain	14.4%	15.2%	Windsor et al., 2025
Commercial chaga “fermented grain” (4 products)	1.0–6.9%	33–68%	Windsor et al., 2025

The 2016 figures were presented by Nammex’s founder at a mushroom-science conference and reported in the trade press, not published in a journal (NutraIngredients, 2017). One detail matters for chaga: what’s harvested is a sterile canker on birch, not a fruiting body, so its numbers aren’t a stand-in for other species.

Are there other markers besides beta-glucan?

Some, but none you’ll find on a coffee label. Ergosterol, a sterol made by fungi, can serve as “a proxy for fungal biomass”, but the same study says it “cannot authenticate” a product on its own (Windsor et al., 2025). Species-specific compounds are another route: in lion’s mane, hericenones have been isolated from the fruiting body and erinacines from the mycelium (Li et al., 2020). The CEO of a Finnish mushroom-extract company has argued that beta-glucan became “an easy win, something to point to on a label” and that quality should be judged on species-specific compounds as well (NutraIngredients, 2025). That’s a reasonable point, and also a sales position.

When is mycelium legitimate?

When it’s mycelium, not grain. Mycelium can be grown in liquid culture, with no grain to carry over. In the 2025 study, a grain-free chaga mycelium sample had more beta-glucan than any of the whole chaga samples, though it differed in other compounds (Windsor et al., 2025). At least one published placebo-controlled human trial of lion’s mane used mycelium “grown in a submerged liquid medium” in industrial fermenters rather than a fruiting body; several of its authors were paid by the company that makes that ingredient (Li et al., 2020). So “mycelium” on a label isn’t a red flag by itself. “Mycelium cultured on oats” with no starch figure is.

What labels say, and what it means

On the label	What it tells you
“Fruiting body extract”	The mushroom itself, extracted. Still worth checking for a beta-glucan figure.
“Mycelium”, “mycelial biomass”, “myceliated”	Mycelium. Ask: grown on what?
“Cultured on organic oats / brown rice / sorghum”	The grain is in the powder.
“Full spectrum”	Often fruiting body plus mycelium on grain. Ask for the split.
“Mushroom” alone	Not enough to know. Four lion’s mane products labeled “mushroom” in one ConsumerLab review were made from mycelium (ConsumerLab, 2022).
“Polysaccharides 30%”	Counts starch. Not a measure of mushroom content.
“Beta-glucans 25%” plus a starch figure	The most informative pair you’ll get.

Our mushroom coffee label checklist turns this into checks you can run on a tub in a minute, including a rough iodine test for starch.

What the evidence does and doesn’t show

• Total polysaccharide tests count starch: strong. It follows from how the assay works, and the validated method exists to separate the two (McCleary & Draga, 2016).
• Grain-grown mycelium products are mostly starch: early. The results agree, but the sample sets are small and were tested by a fruiting-body supplier (NutraIngredients, 2017; Windsor et al., 2025).
• Labels don’t always match the contents: strong that it happens. Independent testing of 19 reishi supplements bought in the US found only 5 matched their labels, and found starch-like polysaccharides, commonly used as fillers, in 13 (Wu et al., 2017, University of Macau with the US Pharmacopeia). ConsumerLab found a mushroom “coffee” powder with “much less beta-glucan than expected from its label” (ConsumerLab, 2022). How often it happens in mushroom coffee specifically: unknown.
• Beta-glucan as the single quality score: mixed. It’s the best-standardized number, but it misses species-specific compounds and can pick up oat beta-glucan.
• Fruiting body vs mycelium makes a difference you’d notice: none. We found no human trial comparing the two in a finished drink, so we make no claim either way.

FAQ

Is mycelium on grain unsafe? None of the sources here tested safety, and none suggests a problem. The issue they raise is value: a product that’s mostly grain means paying mushroom prices for oats or rice.

Is fruiting body always the better buy? Not automatically. A token amount of fruiting body, or a mislabeled one, tells you less than a grain-free mycelium extract with a test result behind it. Our judgment: an honest label and a batch test matter more than which part is used.

Does mushroom coffee do anything? That’s a separate question from what’s in the tub, and we don’t answer it here. If you take medication or are pregnant, ask your doctor or pharmacist before adding a mushroom supplement.

How do I find out without a lab? Ask the brand for a certificate of analysis (COA) for your batch that shows beta-glucan and starch. If it only shows “polysaccharides”, or they won’t send one, that’s your answer.

Sources

• Penn State Extension, “Seeding Substrate and Management of Growing Agaricus bisporus”. Link, retrieved 2026-10-21.
• Penn State Department of Plant Pathology, “Spawn Preparation”. Link, retrieved 2026-10-21.
• McCleary BV, Draga A. “Measurement of β-Glucan in Mushrooms and Mycelial Products.” Journal of AOAC International, 2016. DOI, abstract retrieved 2026-10-21. The lead author founded Megazyme, which sells the assay kit.
• Windsor C et al. “Comparative Study of Chaga (Inonotus obliquus) Dietary Supplements Using Complementary Analytical Techniques.” International Journal of Molecular Sciences, 2025. Link, retrieved 2026-10-21. Five of six authors are employed by Nammex, which sells mushroom extracts.
• Wu DT et al. “Evaluation on quality consistency of Ganoderma lucidum dietary supplements collected in the United States.” Scientific Reports, 2017. Link, retrieved 2026-10-21.
• Li IC et al. Pilot double-blind placebo-controlled study of erinacine A-enriched Hericium erinaceus mycelia. Frontiers in Aging Neuroscience, 2020. Link, retrieved 2026-10-21. Several authors are paid by the ingredient’s maker.
• ConsumerLab, “Best Lion’s Mane and Chaga Supplements”, 2022-10-06. Link, retrieved 2026-10-21.
• NutraIngredients, “Most companies understand green herbs, vitamins, minerals but they don’t understand mushrooms, fungi: Nammex”, 2017-03-16. Link, retrieved 2026-10-21. Nammex sells mushroom extracts.
• NutraIngredients, “Mushroom expert calls for quality quantification beyond ‘easy win’ beta-glucans”, 2025-09-26. Link, retrieved 2026-10-21. The expert runs a mushroom-extract company.
• Vegconomist, “The functional mushroom label problem, and three questions that settle it” (guest post by the co-founder of a mushroom farm). Link, retrieved 2026-10-21.