Cordyceps

Cordyceps is a genus of sac fungi (Ascomycota) whose members are largely internal parasites of insects and other arthropods, a lifestyle described as entomopathogenic ^[1]. The name joins the Greek word for club with a Latin root for head, reflecting the club-shaped fruiting bodies many species send up from an infected host ^[1]. Historically the genus was very broad, but molecular phylogenetic work published in 2007 showed it was not a single natural group and split many former members into separate genera such as Ophiocordyceps and Metacordyceps, leaving Cordyceps militaris as the type species ^[1].

Most Cordyceps species infect a host, grow through and replace its internal tissue with fungal mycelium, and then push up a stalked structure bearing spore-forming perithecia ^[1]. The released ascospores go on to infect new hosts ^[1]. This striking parasitism, in which the fungus consumes the insect and erupts from its body, has made the genus a popular subject in natural history.

Two members dominate human interest. The caterpillar fungus, which parasitizes moth larvae on the Tibetan Plateau and was formerly called Cordyceps sinensis, has been used in Chinese and Tibetan medicine for centuries and ranks among the most expensive medicinal fungi in the world ^[2]. Cordyceps militaris, the type species and the original source of cordycepin, is far easier to cultivate and now supplies much of the commercial market ^[2][4].

Research on Cordyceps has focused on constituents such as the adenosine analog cordycepin, adenosine itself, and cell-wall polysaccharides, which have been studied for possible immune-modulating, anti-inflammatory, antioxidant, and antifatigue effects ^[2]. A small double-blind trial of a fermented Cordyceps sinensis preparation (Cs-4) in healthy older adults reported improvements in metabolic and ventilatory thresholds during cycling, although maximal oxygen uptake did not change ^[3]. Overall, reviewers note that clinical studies remain few and often low in quality, so therapeutic potential is still unproven ^[2].

Cordyceps is not an approved drug; in Western markets it is sold as a dietary supplement or food, typically as dried fruiting body, milled powder, or hot-water and alcohol extracts, and increasingly as laboratory-cultivated C. militaris rather than wild-harvested caterpillar fungus ^[2][3]. Because wild caterpillar fungus is scarce and costly, adulteration and species mislabeling are recognized concerns ^[2].

Generally well tolerated, with mild GI upset the most common complaint. Because it modulates the immune system, people on immunosuppressants or with autoimmune conditions should be cautious. It may also have mild blood-thinning and blood-sugar-lowering effects, so watch for additive interactions.