One Saturday last May, Shane Heath woke up with an idea: the young serial entrepreneur would market the drink he had been sharing with friends in Venice Beach – a muddy concoction of tea, cocoa, spices and four kinds of mushrooms – to the wider world. “Over the weekend I designed the brand, ordered a minimal amount of inventory, and put up a website,” says Heath. By Tuesday, he was online selling 15-serving tins of the dry drink mix he dubbed Mud\Wtr for $30 each. Six months later, revenues exceeded six figures, he says, and with the start of the new year, “we secured a million-dollar investment fund and moved into an office in Los Angeles”.

Mushrooms are having a moment. And the market goes far beyond the portobellos, shiitakes and button mushrooms you find in the produce section. Whole Foods named so-called “functional mushrooms”, used for centuries in traditional medicine, as one of the top 10 food trends of 2018. Suddenly, exotic varieties such as reishi, chaga, cordyceps and lion’s mane are turning up in everything from powders and extracts to coffees, teas, smoothies, broths, chocolates, face creams and shower gels.

US sales of mushrooms accounted for nearly $5bn in revenue in 2017, according to the market research firm Grand View Research, and the market is projected to rise to $7.4bn in the next three years.

Heath freely admits that the draw is not so much the earthy flavor, but the idea that consuming mushrooms will make you feel and perform better. According to the Mud\Wtr website, chaga mushrooms “provide energy and mood enhancement”, cordyceps “increase vitality and endurance”, lion’s mane “improve brain function” and reishi “fight off tumor and cancer growth”.

Mud\Wtr joins scores of other companies selling products that tout mushrooms as a magic elixir. Dried mushroom powders from Om Mushrooms, for example, have “anti-aging properties to retain your youthful vibrance” and “harmonize your longevity, energy and spirit”. Moon Juice promotes Brain Dust, featured on Gwyneth Paltrow’s website Goop, as “edible intelligence” that will “help combat the effects of stress to align you with the cosmic flow for great achievement”.

Some won’t be surprised to learn that even Alex Jones has discovered mushrooms. His infamous Infowars website sells Wake Up America: Immune Support Blend coffee infused with mushroom extracts celebrated for “enhancing immune response and physical stamina”.

“It’s possible that some of these compounds have got really remarkable properties,” says Nicholas Money, PhD., biology professor at Miami University in Ohio. But his 2016 review of the evidence published in the journal Fungal Biology found that marketing claims go far beyond what is supported by the science.

“It’s outrageous,” he says. “People are making a great deal of money from compounds of unspecified chemical nature without experimental evidence to show that they have any benefit.”

Magic shrooms

Mushrooms traditionally associated with medicinal properties are not always tasty on their own. (Chaga, for example, has the taste and texture of tree bark.) But from a nutritional standpoint, the varieties we commonly nibble on and cook with are quite good for you. Edible mushrooms are low in calories (one cup of raw sliced white mushrooms is only 16 calories), rich in protein and fiber, and a good source of B vitamins as well as minerals such as potassium, copper and selenium.

Mushrooms also contain unusually high amounts of the antioxidants ergothioneine and glutathione, according to a 2017 study conducted at Pennsylvania State University published in the journal Food Chemistry. Antioxidants are known for protecting cells from damage associated with diseases such as cancer, heart disease and Alzheimer’s.

And mushrooms do have at least one “magic” property: like people (and unlike plants) they can convert ultraviolet light from the sun into vitamin D. Outside of a few types of fatty fish and fortified dairy products, mushrooms are one of the only good dietary sources of the essential vitamin.

The catch is that commercial farms often grow mushrooms inside says Katherine Phillips, PhD, a senior research scientist at Virginia Tech University. She was a co-author on a study for the US Department of Agriculture that found that the mushrooms Americans commonly buy at the grocery store often contain little vitamin D.

You can buy mushrooms labelled “vitamin D enriched”, which indicates that they were exposed to ultraviolet light, but those often cost more, says Phillips. Instead, she suggests going the DIY route: “Our research found that setting sliced mushrooms outside on aluminum foil for as little as 15 minutes enhances the vitamin D content by at least 25%,” she says. If you use whole mushrooms, she advises laying them gills up, where the concentration of D-producing compounds are highest.

Mushrooms as medicine?

In addition to eating mushrooms, cultures around the world have used them medicinally for thousands of years. The Greek physician Hippocrates identified the amadou mushroom as good for reducing inflammation and cauterizing wounds around 450 BCE. Ötzi the Iceman, preserved in the Italian alps for some 5,300 years, was discovered with whipworm eggs in his digestive tract and, probably not coincidentally, a leather strap around his neck threaded with mushrooms that are known to kill intestinal parasites.

Chinese medical texts dating back to as early as 206BC describe reishi as a tonic against ageing. Widespread use of medicinal mushrooms continues in Asia today, with more than 100 varieties used just to treat cancer.

You need only look to the psychoactive effects of hallucinogenic mushrooms and the toxicity of poisonous varieties to understand that mushrooms can have potent biochemical effects says David Hibbett, PhD., a mycologist (mushroom expert) and professor of biology at Clark University in Worcester, Massachusetts. “Mushrooms produce a lot of interesting chemical compounds that could be defensive,” he says, and that might be useful for fending off bacteria and other bodily invaders that make us sick. “Fungi produce some of our most important drugs,” says Hibbett, pointing out that both penicillin and cholesterol-lowering statins were derived from fungi, the category of organisms that includes mushrooms.

One of the best-studied types of medicinal mushroom is turkey tail, so named because it grows in autumn-color rings resembling feathers. Studies in humans and animals suggest that a component of turkey tail, polysaccharide-K (PSK), may stimulate the immune system. In clinical trials, the supplement appeared to improve survival for people with gastric or colon cancer and, although the evidence is not as strong, may also benefit those with other types of cancer.

Several clinical trials show that a similar compound, lentinan, extracted from shiitake mushrooms, extends survival in patients with stomach, prostate, colorectal and liver cancers when combined with chemotherapy. Both PSK and lentinan are approved in Japan as an addition to conventional therapies for treating cancer.

Other varieties show promise, but for the most part research has not progressed beyond test tubes and animal studies. Those studies have found that, as with turkey tail and shiitake, components found in reishi mushrooms may strengthen the immune system to fight cancer. In mouse studies, researchers found that extracts from chaga mushrooms enhanced learning and memory, reduced inflammation, increased exercise endurance and lowered blood sugar. Lion’s mane mushrooms have been found to speed wound healing and help repair nerves in injured rats.

There’s a dearth of evidence from clinical trials on whether those varieties help prevent or treat disease in humans.

“Medicinal mushroom advocates take an absurd leap when they refer to studies on the effects of single compounds on cultured cells or lab animals as evidence for the potency of powdered mushrooms,” says Money. “It is impossible, for example, to link the immunological consequences of injecting mice with cell wall polysaccharides to the expediency of drinking hot tea brewed from shiitake,” he states in his review.

“Is there any evidence for an anti-ageing effect of smearing mushrooms on your eyelids?” asks Money. “I seriously doubt it.”

Even Paul Stamets, a mycologist and mushroom enthusiast – prominently featured in Michael Pollan’s 2018 book How to Change Your Mind – is somewhat circumspect in describing the benefits of products sold by his company Fungi Perfecti, which account for more 60% of the mushroom supplement market. “At this point the FDA only allows us to say that mushrooms have antioxidant properties, support the immune system, and support general health – that’s as far as we can go,” he says. “Without clinical studies in humans, it’s difficult to separate fact from fiction.”

But Stamets, who says Fungi Perfecti has experienced “explosive growth” in the last few years, says mushroom research is picking up and is on the brink of major breakthroughs. “I know of no other science that has been so underfunded and understudied and yet has such a tremendous potential for human health,” he says. “There’s a flood of knowledge coming downstream into the public consciousness.

Money is actually optimistic as well. “I think that there is a potentially an exciting future when we do find some very active compounds that are extremely useful in a therapeutic setting,” he says. “We’re just not there yet.”

About those health claims …

If claims for mushroom products sound both extraordinary and, at the same time, somewhat vague, that’s intentional. Unlike drugs, nutritional supplements are only loosely regulated by the Food and Drug Administration (FDA) – manufacturers can stretch health claims as long as they don’t say that a product will diagnose, treat, cure or prevent disease. To avoid undue scrutiny, manufacturers of supplements and functional foods skirt that line without actually crossing it, says Money. A company may talk about mushroom products as “immune activators”, for example, without stating explicitly that heightened immunity wards off illness.

That means, says Money, you should take those claims with a large dose of salt.

Heath says he has done his own research and is convinced of the health benefits of his ingredients but, nonetheless, is careful not to oversell. “We don’t claim it [Mud\Wtr] is going to make you a superhuman,” he says. “You can drink it and over time it will give you benefits the same way vitamins do.”

Another byproduct of lax regulation is that supplement makers don’t have to prove to the FDA that products are safe and effective – or even that they contain what the label says. A 2017 study published in the journal Nature found that only five of 19 brands of supplements contained the amount of reishi mushroom stated on the label.

If you want to try a mushroom supplement, Money and other experts we talked to recommend looking for a seal from an organization known for certifying products: ConsumerLab.com, NSF International, US Pharmacopeia (USP) or UL. There is no guarantee that a supplement will help and not hurt you, but it does provide some assurance that it contains the advertised ingredients and is free from harmful contaminants.

Stamets recommends looking for products based on US Department of Agriculture-certified organic mushrooms sourced in the US. “Mushrooms mirror the environment in which they are grown,” he says. “Even products labelled organic grown in an area of China where air pollution is high, for example, may contain contaminants that fly under the radar of testing organizations.”