Medicinal mushrooms research: separating evidence from hype

Which mushrooms are being studied, and for what

The term "medicinal mushrooms", or "functional mushrooms" in US marketing, usually covers a group of species with a long history in traditional medicine and an active research literature today:

• Reishi (Ganoderma lingzhi and related species), studied mainly for its polysaccharides and triterpenes. North America has its own native relatives, such as the hemlock varnish shelf.
• Turkey tail (Trametes versicolor), source of the protein-bound polysaccharides PSK and PSP.
• Lion's mane (Hericium erinaceus), studied for compounds called hericenones and erinacines.
• Shiitake (Lentinula edodes), source of the beta-glucan lentinan.
• Cordyceps militaris, studied for cordycepin.
• Chaga (Inonotus obliquus), a sterile growth on birch rich in pigments and phenolic compounds.

Fungi are also the origin of major medicines that are not "medicinal mushrooms" in the popular sense, such as penicillin, whose mass production was developed at a USDA laboratory in Peoria, Illinois, during World War II.

What the evidence shows so far

Most research on medicinal mushroom compounds comes from lab studies on cells and from animal experiments. These are useful for generating hypotheses but cannot show that a product benefits people. Human trials exist for some species and preparations, yet many are small, short, use different extracts and doses, or lack proper control groups, which makes results hard to compare. In Japan, PSK and lentinan have been studied as add-ons to conventional cancer treatment, but that research concerns specific standardized preparations, not supplements in general.

A fair summary is that the field is scientifically interesting and still largely unproven for most uses claimed online. Learning to read study designs, effect sizes and systematic reviews is the core skill for anyone working in this area.

Quality, identity and safety of products

Two products labeled with the same species can be very different. Key questions include whether the product contains fruiting bodies or mycelium, whether the mycelium was grown on grain and contains a large share of starch, which extraction method was used, and whether beta-glucan content was measured with a specific method. DNA testing helps confirm species identity. Products can also contain contaminants such as heavy metals, and case reports have linked some products to adverse effects, for example high oxalate levels in chaga. Anyone taking medication or with a health condition should talk to a doctor before using mushroom supplements.

How mushroom supplements are regulated in the US

In the United States, most mushroom products are sold as foods or as dietary supplements under the Dietary Supplement Health and Education Act. The FDA does not approve dietary supplements before they are marketed; manufacturers are responsible for making sure their products are safe and properly labeled, and a new dietary ingredient requires a notification to the FDA at least 75 days before marketing. A product marketed to treat, cure or prevent a disease is regulated as a drug. Structure/function claims are allowed but must carry the disclaimer that the statement has not been evaluated by the FDA and that the product is not intended to diagnose, treat, cure or prevent any disease. Not every fungus is acceptable: in December 2024 the FDA stated that Amanita muscaria and its constituents are not authorized as ingredients in conventional food.

Studying medicinal mushrooms at Fungaris

Our medicinal mushroom school teaches the topic as a science: biology of the species, chemistry of bioactive compounds, extraction and analysis, critical reading of clinical evidence, safety and regulation in the US and the EU. The courses do not train practitioners to treat patients and make no health claims for any product.