Between California serving its coffee with a cancer warning and the United States leaving the International Coffee Organization on Tuesday, coffee’s been having a rough press week. But bean freaks still need their morning fix, which is perhaps why the internet is going crazy for a java alternative: mushroom coffee. The weird concoction is purported to get you going without any of the side effects of your regular brew.

Mushroom coffee, which is pretty much powdered mushrooms stirred into a regular coffee, has been around for several years but is enjoying a resurgence of attention, thanks to an article in the Telegraph published last week. What makes it so healthful, according to Four Sigmatics, the specialty mushroom company that’s been leading the push since 2012, is that mushroom contains energy-boosting compounds that don’t have the negative side effects of caffeine. The company, and others like it, mostly use four “medicinal” mushroom species in their formulations: chaga, lion’s mane, reishi, and cordyceps.

Four Sigmatics states on its website: “Chaga is alkaline forming. This helps improve your energy and metabolism.” Other varieties promise similar effects: cordyceps helps “sustain steady energy”; lion’s mane supports “focus, creativity, memory, concentration, and brain health.” There aren’t any clinical studies supporting these particular claims about these specific products, but that’s not to say there are no studies on mushrooms’ medicinal effects. Mushrooms definitely have unique, occasionally bioactive compounds — just take a look at the notoriously psychedelic psilocybin mushroom. It’s just not clear that the effects that are being touted alongside mushroom coffee are the same ones that have been characterized by scientists.

Chaga
Chaga mushroom is one of the species used in mushroom coffee.

There’s evidence of early Greek, Egyptian, Roman, Chinese, and Mexican civilizations using mushrooms for their medicinal purposes, but more recently studies have taken a stab at better characterizing those health benefits. Researchers described them in a 2014 Journal of Nutrition review of the health effects of mushrooms in general:

Some preclinical and clinical studies suggest impacts of mushrooms on cognition, weight management, oral health, and cancer risk. Preliminary evidence suggests that mushrooms may support healthy immune and inflammatory responses through interaction with the gut microbiota, enhancing development of adaptive immunity, and improved immune cell functionality.

a miniature forest
Lion's mane mushrooms may have neurogenic properties.

Studies on the effects of specific mushroom species are scarce, and those that do get published often appear in less mainstream, fringe journals — perhaps because medicinal mushrooms are usually considered a part of complementary, alternative, or integrative medicine (that is, its use wasn’t developed through strictly Western medicine practices).

For example, one review in the journal Evidence-Based Complementary and Alternative Medicine in 2014 described a study on bioactive compounds from reishi mushrooms that exerted anti-cancer effects through their immune-boosting activity. In the Journal of Traditional Complementary Medicine in 2012, a review on mushrooms used in traditional Chinese medicine noted that cordyceps has traditionally been used to “treat fatigue.” Lion’s mane was shown to boost neuron growth in a paper in the International Journal of Medicinal Mushrooms in 2013.

Details on how these mushrooms exert these effects, however, are lacking.

Cordyceps militaris
Cordyceps mushrooms have long been used in traditional Chinese medicine to treat fatigue, though its mechanisms are not known.

In its database of medicinal herbs used in integrative medicine, New York’s Memorial Sloan Kettering Cancer Center lists the effects of many of the mushrooms used in mushroom coffee but is careful to mention that those uses are “purported.” Chaga mushrooms fight cancer, reduce inflammation, stimulate the immune system, and protect the liver; reishi mushroom is said to treat fatigue, among other health issues; cordyceps, meanwhile, has been used to treat kidney failure and stimulate the immune system. It doesn’t list any information on lion’s mane, though.

For a weird health trend that’s been approved by dangerously pseudoscientific websites like Goop, mushroom coffee seems pretty harmless, though whether it really delivers the effects it promises is a different story — scientists probably won’t reach a consensus until more research is published in more mainstream journals. It might be providing those effects, or it might have health effects that scientists don’t know about yet. Or, it might just be another fad fueled by the placebo effect (which shouldn’t be discounted!). Whatever the case, it’s now being packed into “Healthy Trendsetter Boxes” at Wal-Mart for $29.99, so the product is likely here to stay, though whether it will retain its hipster cred remains to be seen.