The phrase "fruiting body" tells you which part of the mushroom is in the jar, and it is one of the few specs on a mushroom supplement that is specific enough to compare between brands.
Fruiting body
The mushroom itself — the part you would recognise as a mushroom. It is what has traditionally been used and what most of the research uses.
Mycelium on grain
Mycelium is the root-like network the mushroom grows from. It is commonly cultivated on grain, and the usual industrial practice is to harvest and mill the whole thing — mycelium plus the grain it grew on. That grain ends up in the powder, and it is why a "mushroom extract" can contain a substantial proportion of starch.
This is legal and disclosed, in the sense that the label says "mycelium". It is just not obvious what that implies.
The number that settles it
Look for a stated beta-glucan percentage. Beta-glucans are the cell-wall compounds a lion's mane extract is standardised to, and a stated percentage is a specification a brand can be asked to substantiate. It is a separate assay from the identity, heavy-metal and microbial panels a lot certificate usually carries.
If a label states only "polysaccharides", that is a broader category that includes starch — so a grain-heavy product can post a high polysaccharide number and look impressive. A stated beta-glucan percentage cannot be inflated the same way.
So: fruiting body, and a beta-glucan percentage. If a label gives you both, it is telling you what you bought. If it gives you neither, that is information too.
Where we stand
Weal Focus prints both: 100% fruiting body, standardised to at least 25% beta-glucans, at 400 mg. That is the least a label can do, not the most.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
Sources for the claims and figures on this page, with the population studied in each, are on our citations page.