The mushroom business is booming. Worldwide production is up 30-fold since the late 1970s, and the average person now eats about 11 pounds of mushrooms per year, according to a 2017 analysis of the global mushroom industry.

One of the factors driving this mushroom mania is the belief that they possess unusual and profound health attributes. A 2018 report from the Royal Botanic Gardens points out that mushrooms and other fungi have been used as medicine for nearly 6,000 years. Whole Foods even named “medicinal mushrooms” as one of its top food trends for 2018. In particular, many exotic and esoteric types like reishi and chaga mushrooms are now turning up in powders, pills, and other health supplements.

All this hype is not unfounded. “Mushrooms are fungus, and some famous medicinal items—including penicillin and statin drugs—were derived from fungus,” says Dr. Mark Moyad, the Jenkins/Pomkempner Director of Preventive and Alternative Medicine at the University of Michigan Medical Center. He says it’s reasonable to think that one of the very few fungi humans eat could provide some benefits not associated with the consumption of fruits, vegetables, or other types of foods. Based on what we already know about mushrooms, he calls them “a winner for almost all people and all diets.”

For starters, all mushrooms—even standard white ones—are low in calories and contain healthy nutrients like potassium, selenium, and vitamin B12, Moyad says. Mushrooms are also among the very few natural and vegan sources of dietary vitamin D, he says, and they contain a type of soluble fiber called beta glucan, which seems to have heart and cholesterol benefits.

But the research really gets interesting when it comes to mushrooms’ antioxidant compounds.

Mushrooms contain glutathione, an antioxidant molecule found in almost every cell in your body. It seems to have important signaling and detoxifying properties, says John Richie, a mushroom researcher and professor of public health sciences at Penn State University. “[Glutathione] is one of the most important small molecules in living things, and it plays a role in turning on or turning off the cell’s protective systems,” Richie says.

While antioxidants get a lot of hype, he says they’re often misunderstood. “One of the problems is that, once they do their job, antioxidants can become pro-oxidants, which is a problem,” he says. He highlights an infamous study, conducted in the 1990s, that found tobacco users who took supplements loaded with the antioxidant beta-carotene experienced increased rates of cancer, rather than the decreased rates the study’s leaders had anticipated. “The simple idea that antioxidants will solve all your problems is very naïve,” he says.

But when it comes to glutathione, he says, “We have this whole system of enzymes that is designed to take care of glutathione and supplement its activity. It stands out from other antioxidants from the standpoint that it’s one we evolved to use in our cells.”

Along with glutathione, mushrooms contain a second antioxidant called ergothioneine, which Richie says is much less abundant in other foods. But while ergothioneine is rare, it turns out that the human body contains a specific transport protein for it. “This suggests it’s got to be important for human health,” he says. Important how? Richie says there’s preliminary evidence that ergothioneine could block the kind of oxidative damage that contributes to cancer and neurodegenerative diseases like Alzheimer’s. There are also studies linking the consumption of ergothioneine to a longer, healthier life.

“Mushrooms are highly unusual in that they’re a producer of both glutathione and ergothioneine,” Richie adds. This, combined with mushrooms’ other salubrious properties and millennia-old associations with health and medicine, gives him and other researchers reason to believe these fungi really could possess some “superfood” properties.

When it comes to hyped specialty mushrooms—such as reishi or chaga—there’s some evidence of additional health perks. One 2011 review linked reishi mushrooms (or extracts containing their compounds) to better blood sugar regulation, protection against liver and gut disease, and “anticancer effects.” Some of these same benefits have turned up in research on chaga mushrooms. But the authors of that 2011 review point out that nearly all the evidence to date comes from animal or lab models—not from studies on humans.

Moyad reiterates these concerns. He also says that some varieties of mushroom—including reishi mushrooms—have effects on blood clotting that may make them risky for people taking warfarin or other blood pressure meds. Reishi mushroom supplements may also present some risks for those undergoing chemotherapy or taking immunosuppressant drugs, according to a report from Memorial Sloan Kettering Cancer Center.

Especially when it comes to mushroom supplements, “we need more studies that are independently funded”—meaning not paid for by companies trying to sell mushroom-derived products—“and larger in size and longer in duration, and that incorporate some kind of placebo control,” Moyad says. The long-term effects of using these products aren’t known.

Moyad says adding more whole mushrooms to your diet is a safe way to get their potential health benefits while avoiding the risks that come from taking pills or powders.

How much should you be eating? “I recommend that everyone consume about three milligrams a day of ergothioneine from mushrooms,” says Robert Beelman, professor emeritus of food science at Penn State and a frequent collaborator of Richie’s. According to a 2019 review Beelman and Richie co-authored, swallowing a hearty 3.5-ounce portion of button mushrooms every day—or just an ounce of specialty mushrooms like shitake, oyster, or maitake mushrooms—will provide those three milligrams. And no, you don’t have to eat them raw. “Cooking does not destroy the ergothioneine at all and might actually make it more bio-available,” Beelman says.

So, at least for now, skip the supplements. Instead, just add more mushrooms to your diet.