Mushrooms have been used in Eastern medicine for centuries to treat everything from asthma to gout.
Now they're being marketed in the West as functional or medicinal mushrooms that can prevent cancer or stimulate higher brain function, but there are relatively few trials in humans to back up these claims.
There are more than 2,000 species of edible mushrooms on the planet, but many of us probably only know a few kinds. Sauteing or grilling up white button mushrooms and portobellos may sound familiar to Americans, but in other parts of the world, particularly Asia, soups and stews might contain shiitake, maitake, oyster or lion's mane.
To find a really good variety of mushrooms, I went to my local Mitsuwa, a Japanese market chain, located at a busy intersection on the west side of Los Angeles. It's pretty drab outside, but when you walk in the doors, there's lots of color and sound: Japanese snacks in bright packages, an aisle of nothing but singing rice cookers, and a rainbow array of mochi ice cream, the Japanese answer to an ice cream sandwich.
Vendors hawk steaming bowls of ramen and freshly fried tempura on one side of the building. And on the other side, there's the produce aisle, which includes rows and rows of mushrooms.
Manager Yumi Kuwata buys the mushrooms here and says her top sellers include shimeji (beech mushrooms,) enoki (tiny white mushrooms with small caps) and shiitake, but she always has at least 10 varieties.
Kuwata says her customers buy mushrooms because they're healthy and low in calories. "Japanese food [is] very healthy cuisine. So that's what they are expecting," she says.
But mushrooms offer a lot more than low calories.
Viki Sabaratnam, the scientist in charge of the mushroom research center at the University of Malaya in Kuala Lumpur, Malaysia, says mushrooms are particularly good for us because of what they do before humans harvest them: "Their basic function in the environment is recycling of large molecules, and in the process they produce these fruit bodies, we call them, and they accumulate some of these components."
The components include dozens of nutrients like selenium, vitamin D, potassium and compounds known as beta glucans, which can help fight inflammation in the body. Chronic inflammation can contribute to many diseases of aging, such as cancer, Parkinson's disease, and dementia. Think of mushrooms as the superheroes of the fungi kingdom.
But research on actual humans hasn't been as prolific.
There are a few outliers: Shiitake mushroom extracts seem to help prolong the lives of stomach cancer patients undergoing chemotherapy, and in fact doctors in Japan now prescribe them for that purpose.
It's hard to draw big conclusions about how these extracts would impact a broad range of people, though, because the studies have been small and targeted to specific populations.
Sabaratnam is studying how mushrooms might someday help fight off dementia, which affects around 50 million people today, with 10 million more added every year.
She and her team reviewed studies of 20 different medicinal mushrooms thought to improve brain function and about 80 different metabolites isolated from those mushrooms that were tested in cells in the lab and in mice. They found that these metabolites improved recovery and function in damaged neural cells and had antioxidant and anti-inflammatory benefits.
"We have shown in lab experiments, yes, some of these properties are there," But as she admits, "it's quite a long way to go" to say how these mushroom extracts will work in actual humans.
But that hasn't stopped the dietary supplement industry from jumping on reports of mushroom health benefits. There are teas, coffees and pills containing extracts of mushrooms that promise to reduce stress or jump start your brain.
Megan Ware is a dietitian in private practice in Orlando. She sees the potential health benefits of mushrooms, and even drinks mushroom coffee when she wants to feel extra alert. But she warns: "If you're eating cheeseburgers and fries for lunch every day and you eat a couple mushrooms along with it, that doesn't mean it's going to lower your risk for heart disease or diabetes or any of those lifestyle conditions."
As boring as it sounds, a balanced, healthy diet and regular exercise are still the best ways to prevent disease. "I would caution against calling any food magical," Ware says.
Maybe one day, science will be able to prove that mushrooms can help prevent and treat disease. And if not, well, mushrooms are really delicious, so why not add a few new ones to your diet?
Here's a list of a few tasty mushrooms that also show promising health benefits: