What is a mushroom really? Two titans of the wellness world duke it out

Their friendship was rooted in a mutual love of mushrooms. Paul Stamets and Jeff Chilton met in 1978 in Olympia, Wash. Back then, Stamets was a student and aspiring mycologist, and Chilton was a commercial mushroom grower. Their intellectual bond grew so strong that in the coming years they wrote a book together: The 1983 home mushroom grower guide “The Mushroom Cultivator.” It became a bible for aspiring and amateur mycologists that still sells 5,000 copies per year, according to Chilton, establishing the duo as the trailblazers in the popularization of all things fungi. For many years, they remained close. Chilton was even best man at Stamets’ first wedding.

Despite writing a cult classic text together that many people credit as the reason they started growing fungi, Stamets, 69, and Chilton, 77, are now at odds over the fundamental question of what constitutes a mushroom. Is it a “fruiting body,” better known as the toadstool, that emerges from the ground in a panoply of shapes and textures? Or could a mushroom also be synonymous with its fungal roots, otherwise known as mycelium, from which the fruiting bodies sprout?

This disagreement is not just a personal one between Stamets and Chilton. It’s one in which millions of dollars are potentially at stake, along with consumer trust. Mushrooms like reishi, lion’s mane, chaga and turkey tail are big business in the U.S., with consumers taking them in an effort to bolster brain and gut health, even though purveyors of such supplements are cautious not to make specific claims about their products. Still, mushroom supplement packaging has been known to include phrases like “immune support,” “digestive health” or “supports mental clarity.”

Jeff Chilton, left, holds a shiitake log. Paul Stamets, right, attends “How Psilocybin Mushrooms Can Help Save the World” during SXSW 2023.

(J. Chilton; Nicola Gell / Getty Images for SXSW)

Thanks to a “shroom boom” partly turbocharged by increased interest in both the aesthetic and psychedelic qualities of mushrooms, news of the potential health benefits of nonpsychedelic mushrooms has spawned a growing supplement market for so-called “adaptogenic mushrooms” in North America. With each day that passes, it seems mushrooms gain a new convert. Google searches into mushroom supplements have nearly quadrupled over the last five years. Meghan Markle recently spoke of using nonpsychedelic mushroom supplements to manage anxiety and stress, while across the pond, singer Ellie Goulding just launched her own business, specializing in mushroom lattes made of fruiting body extracts.

All of this might not have been possible without Stamets, a bearded man who often wears round tinted glasses and a cap. In 1980, he founded mushroom supplement company Fungi Perfecti, which generated $30 million in annual revenue as of 2020, the most recently reported figure. Chilton wouldn’t provide an exact number, but he says that is comparable with his own family’s two companies’ combined revenues.

Google searches for “mushroom supplement” have increased over the last five years.

(Google Trends)

Chilton prefers to keep a lower profile, but Stamets — the idiosyncratic black belt in tae kwon do — is the iconic face of the ascendant medicinal mushroom movement, thanks to his longtime public evangelizing of many types of mushrooms’ benefits. His 2008 TedTalk on how mushrooms could save the world has more than 5 million views, while the first of his two podcasts with Joe Rogan has 12 million views on YouTube, ranking it among the more popular episodes. In 2019, Stamets starred in the popular Netflix documentary “Fantastic Fungi,” in which he suggests mushrooms could help save humanity from its seemingly inexorable death march. Stamets also has an eponymous Star Trek character named after him, and regularly delivers sold-out keynote lectures all around the world, during which he recounts how an extremely high dose of psychedelic mushrooms supposedly cured him of his stammer at 19.

When Stamets talks about mushrooms, or is photographed with mushrooms, they’re typically toadstools, but he also points to evidence indicating that mycelium has higher overall levels of active ingredients than the fruiting bodies. Accordingly, his company Fungi Perfecti’s Host Defense Mushrooms supplement products are often made solely of mycelium, grown on a rice substrate in the company’s Olympia lab, although some consist of a blend of fruiting bodies and mycelium. Tubs containing pills made up of these fungi are on the shelves of Whole Foods and Sprouts stores across the country and in the supplement aisles of Erewhon across Los Angeles County.

Stamets’ company describes him as “the world leader in medicinal mushroom research,” and he insists that because mycelium is part of the fungal organism, it is therefore a mushroom. “I prefer mushroom fruit bodies for food and tea,” he tells the L.A. Times via email. “I prefer mycelium for supporting immunity, neurological health, microbiome health and for many other benefits. … I know that mycelium is far more immunologically active and beneficial for immune support when taken as a supplement.”

Chilton, who is usually clean-shaven, wears clear rectangular glasses and is a keen trout fisher, founded mushroom distributor Nammex in 1989. The company provides the mushrooms for Real Mushrooms, an online sister firm that sells fungi supplements, and is a rival to Fungi Perfecti. Real Mushrooms’ supplements are made from fruiting bodies, and grown outdoors in China to reduce costs. Chilton is emphatic in his belief that mushrooms are not mycelium, not least since they differ in structure and chemistry, and for more than a decade he has been on a crusade to expose what he believes has been rampant mislabeling across the industry, spawning a tit-for-tat fight that has largely been fought in competing academic papers, podcasts and the gossip chambers of the mycology world.

Then Chilton took the disagreement to a new level. His escalation had been brewing after he petitioned the Food and Drug Administration in 2023 to ensure “mushroom” and “mycelium” are differentiated on supplement labels and to “disclose the presence of any substrate [like oats or rice] on which the fungal ingredient is grown.” In December, he gave a presentation to the agency’s Office of Dietary Supplement Program, claiming that there is “deceptive marketing of dietary supplements and functional foods containing mycelium fermented grain and labeled as ‘mushroom.’” He even called on the FDA to take “appropriate enforcement action” to ensure the safety of mycelium products. It has not.

Parts of turkey tail mushrooms are used in both Fungi Perfecti and Real Mushroom products. Both advertise “immune support” on their bottle labels.

(Altrendo / Getty Images)

Chilton alleges that there are two smoking guns that support his case. Firstly, that mushrooms do not contain starch, but supplements consisting of mycelium grown on grain does. Secondly, that mycelium lacks beneficial compounds like beta-glucans, which are known for certain potential immune-boosting properties and are more plentiful in fruiting bodies.

“Mycelium products made in the U.S. are typically not pure mycelium, they often mostly consist of grain starch,” Chilton tells the L.A. Times in a FaceTime call. “The issue is fermented grain masquerading as mycelium or mislabeled as mushroom. People are being sold grain powder.”

But according to Stamets, “to say that rice substrate, being cultured by mycelium as it grows through it, is just rice, inert or a filler are lies.” He acknowledges that beta-glucans are important, but says that differences in levels between mushroom species are “huge” and that current testing methods struggle to produce consistent results, while citing evidence of his products’ immunological benefit.

His company touts itself as having “complete control” over its supply chain and he has raised questions over the quality of Real Mushrooms’ products, which are typically processed to create extracts and isolate specific beneficial compounds. “Many companies, especially companies importing Chinese mushroom extracts like Nammex, promote their products as being fruit body extracts when, in fact, the liquid extract is sprayed back on the extracted mushroom pulp and then sold as 100% pure extracts,” he says.

Chilton says in response: “Unfortunately, Paul is uninformed about our extraction process. Our hot water extract is never separated from the ground mushroom, ensuring that the important mushroom compounds are in a more bioavailable powder state and nothing is left behind.”

Stamets and Chilton have never debated publicly, but they both claim to have the facts to support their positions. Stamets says despite the relative absence of beta-glucans, the increased levels of other obscure medicinal nutrients found in mycelium eclipse those of fruiting body mushrooms, while Chilton points to hundreds of years of human consumption of mushroom fruiting bodies in Asian traditional medicine systems.

If one man is proven to be right, and another wrong, it could be disastrous for one of their businesses, and the other companies that use similar formulations for their own mushroom supplements. As it stands, the science is somewhat unclear — despite the best efforts of both protagonists — leaving Stamets and Chilton to squabble over whose products are superior. (Chilton’s personal mantra is: “No mycelium, no grain, no starch.” Meanwhile Stamets says: “It is silly to disconnect mycelium from mushrooms.”)

The failure of either party to produce data that a consensus of experts agree on underlines key differences between wellness and pharmaceutical companies. The latter have larger budgets to fund research and stronger motivation: pharmaceuticals need federal approvals and supplements do not. And with no end in sight, Stamets and Chilton’s disagreement is causing ructions in the mushroom community of business people, mycologists and fungi enthusiasts.

“It’s almost like watching your parents fight,” says Dennis Walker, host of mushroom business podcast “Mycopreneur.” “The two godfathers of the industry have divergent opinions on such a fundamental question.” Walker says the sector is split about 50:50 between companies that, like Stamets’, use mycelium-based products, and like Chilton’s, fruiting bodies.

Few mushroom aficionados discuss the row publicly for fear of stoking its flames or discouraging consumers from taking either adaptogenic or psychedelic mushrooms, but “all the mycologists and mushroom people talk about it privately,” Walker adds, disclosing that his podcast has received sponsorship fees from Chilton’s company Nammex. One mushroom expert refused to comment on the issue over concerns of becoming a “pariah.” Another did not want to make an “enemy” of Stamets.

Fungi Perfecti and Real Mushrooms sell lion’s mane supplements. Real Mushroom’s bottle label says it contains no added mycelium while Fungi Perfecti notes it includes mycelium and fermented brown rice biomass.

(Arterra / Universal Images Group via Getty Images)

So, who might be right? It’s complicated, but Dr. Gordon Saxe, executive director of the Krupp Center for Integrative Research at UC San Diego, which conducts research on nutrition and natural medicine, says mycelium products grown on rice substrates “may be even more effective” at aiding health than fruiting bodies. He is also collaborating with Stamets on forthcoming research.

“Mycelium has the advantage that it can be mass-produced under controlled, aseptic conditions, assuring specified levels of key compounds and preventing contamination by undesirable microorganisms and insects,” adds Saxe. “This permits potentially medical-grade, scalable production, something not achievable with fruiting bodies.”

Andrew Weil, an author and founder of the Andrew Weil Center for Integrative Medicine at the University of Arizona, which offers courses fusing alternative therapies including homeopathy and traditional Chinese medicine with conventional medicine, says that he sparked Stamets’ interest in medicinal mushrooms back in the 1970s. Weil appeared on Fungi Perfecti promotional materials for mycelium products holding large mushrooms on a 2016 poster.

But he tells the L.A. Times that he now disagrees with his longtime friend Stamets’ appraisal of the potential benefits, and today recommends people use fruiting body products.

“Both probably have medicinal benefits,” he says. “But it is cheaper to produce mycelial extracts of medicinal mushrooms, and because they include some substrate material on which the mycelia grow, makers of these products are open to the charge that they are selling expensive rice and sawdust.”

Fungi Perfecti and Real Mushrooms both market their reishi mushroom supplements for longevity.

(Yang Meiqing / VCG via Getty Images/VCG / VCG via Getty Images)

“Paul Stamets calling for mycelium to be defined as mushrooms is akin to Michael Jordan calling to move the three-point line,” wrote Robert Johnson, a founder of mushroom product line Mycroboost, in a 2023 Rolling Stone piece.

Jason Slot, a professor in fungal evolution genomics at Ohio State University, says that the data from published studies does not conclusively show that one is more beneficial than the other, but he summed up what is likely the mindset of many consumers who watch mushroom documentaries and then go out seeking to buy fruiting body supplements.

“If you’re not comparing apples and oranges, [and] you want apples, but the oranges are perfect; who cares if the oranges are perfect? You want apples,” he says. “Mycelium is fundamentally different from the mushroom,” Slot adds. “From the ecological perspective of the fungus, it’s doing different things.”

Back in 2015, Fungi Perfecti’s products said prominently on the jar, “made with U.S. grown organic mushrooms.” But in 2017, the American Herbal Products Assn., a trade group, issued guidance calling for more precise labeling in the industry so that the life stage of the fungi from which the product is manufactured is clearly stated. “‘Mushroom’ when used as a noun may be used as a synonym for ‘fruitbody’,” it said. “‘Mycelium’ means the vegetative portion of a fungus.” However, it also supported using the phrase “mushroom mycelium.”

Fungi Perfecti now specifies when its products are made of mushroom mycelium, though the designs are still adorned with mushroom fruiting bodies. It’s unclear whether consumers always know which one they are buying. Or if they know what mycelium means.

Real Mushrooms sells chaga mushrooms in a powder for “digestive health” and Fungi Perfecti includes it as an ingredient in its Stamets 7 Capsules, named after founder Paul Stamets.

(Kendra Stanley-Mills for The Washington Post via Getty Images/The Washington Post / The Washington Post via Getty Images)

“To promulgate a viewpoint that mycelium is inferior or inactive,” Stamets says, “despite the huge body of literature demonstrating the exact opposite is disingenuous marketing at best, a denial of reality, and, at worst, purposeful deception.” On the packaging, he adds: “Our label design includes images of the recognizable fruit body that the mycelium forms. This is normative across dietary supplements. Most echinacea root products have an image of an echinacea flower or plant on the package although the specific extract is made from the root.”

As the mushroom supplement industry surges into the mainstream, the deepening rift between Stamets and Chilton has become a symbolic fault line — not just over fungi, but over how science, storytelling and commerce entwine in wellness culture. Their decades-long friendship, now strained, reflects a wider identity crisis for the industry they helped build: What is a mushroom, really, and who gets to decide? And whose camp will define the next chapter of this booming industry?