Mycelium

The filaments grow on the surface of and inside solid substrates, and send up aerial hyphae, forming a three-dimensional mycelial network [2]. The mushroom that people pick is a different structure, the fruiting body, which usually grows exposed outside the medium while the vegetative mycelium stays mostly underground [1].

The two parts can differ in chemistry. In lion's mane, hericenones are extracted from the fruiting body and erinacines from cultured mycelium, according to a rat safety study run by researchers employed by Grape King Biotechnology [3]. A separate systematic review of preclinical studies also describes erinacines, a group of cyathane diterpenoids, as constituents of lion's mane mycelia [4]. A 2026 review of food-safety-relevant basidiomycete mushroom toxins, with a particular focus on Pleurotus species, reported that these toxins were predominantly present in the fruiting body rather than in mycelium [1].

A product labeled with a mushroom's name may contain mycelium, fruiting body or both, and the two are not interchangeable. The 2026 review describes the general legislative standpoint as being that mycelium safety should not be assumed from fruiting bodies [1]. European records keep the two parts separate: the European Commission's novel food consultation list records a 2019 decision that Hericium erinaceus dehydrated mycelium powder is a novel food, and a 2026 decision that a powder extract from the fruiting body is not novel [5].

When reading a mushroom study, look for which part was used, how it was grown, and which compounds were measured. Findings for a fruiting body extract describe that material, not mycelium products, and vice versa.

For the graded evidence, see Lion's mane.

• Fruiting body
• Novel food
• Botanical extract