Andrew Weil, MD, is a huge fan of mushrooms. A longtime mushroom hunter, he seeks them out because of their taste and health benefits. And Weil, founder and director of the Arizona Center for Integrative Medicine at the University of Arizona Health Sciences Center, likes to share his enthusiasm for these fungi.
"I have always extolled both their nutritional and health benefits, in part to help dispel the general fear of mushrooms...," Weil tells WebMD in an email. He says research supports the use of select medicinal mushrooms for their anti-inflammatory, antibacterial, antiviral, and immune-enhancing properties.
Not all mushrooms are created equal. Weil advises seeking out the more exotic varieties that are becoming increasingly available on supermarket shelves. Here are four that Weil says are particularly good for you:
- Shiitake: Animal studies have shown that these flavorful and readily available mushrooms have anti-tumor, cholesterol-lowering, and antiviral properties. Weil recommends fresh and dried shiitakes.
- Enoki: These slender, mild-flavored mushrooms appear to have significant anti-cancer and immune-enhancing effects, Weil says.
- Maitake: Also known as 'hen of the woods,' these mushrooms may have anti-cancer, antiviral, and immune-enhancing properties. They may also reduce blood pressure and blood sugar, says Weil, who likes to grill maitakes with teriyaki sauce.
- Oyster: Less expensive -- and less flavorful -- than shiitakes, these mushrooms may also provide some protection against cancer, Weil says.
Weil is less enthusiastic about white, or button, mushrooms, a species of mushroom that also includes Portobellos and criminis.
“Button mushrooms do possess some health benefits, but not the general health benefits found in Asian mushrooms,” Weil says.
Weil also says that these commonly available mushrooms contain natural substances called agaritines, which studies show may increase the risk of tumors in animals.
It’s important to keep in mind that mushrooms are not the only food to contain small amounts of potential carcinogens, or cancer-causing substances. For example, acrylamides, which form when certain foods are cooked at high temperature, have caused tumors in mice and rats. They are found in French fries.
Although there’s no conclusive evidence that agaritines found in mushrooms are harmful to people, Weil likes to play it safe. He advises people to avoid eating large quantities of them.
“All told, it is OK to eat button mushrooms in moderation,” Weil says, “but they should always be thoroughly cooked -- broiled or grilled is best.”
Cooking may break down some of the naturally occurring toxins, he says. In fact, Weil advises against eating any mushrooms - wild or cultivated - raw.
Mushrooms offer so much that is good for you, says New York dietician Marjorie Nolan, MS, RD. They are a good source of protein as well as antioxidants such as selenium, which helps to prevent cell damage, and copper, a mineral that aids in the production of red blood cells. In fact, mushrooms are the only produce that contains significant amounts of selenium.
For those who don't like bananas, consider the Portobello mushroom. It has more potassium and fewer calories, says Nolan, a spokeswoman for the American Dietetic Association. Criminis are particularly high in vitamin B12, which is good news for vegetarians, Nolan says, because that's a vitamin more often found in animal products. In general, mushrooms are a decent source of B vitamins. They are also cholesterol free and very low in fat.
White mushrooms are also an increasingly good source of vitamin D because growers are exposing their crops to small amounts of ultraviolet light, which increases their D content dramatically, Nolan says.
"They are good for low levels of vitamin D, which is almost epidemic," Nolan says. "I happen to love mushrooms... they are not at the top of the list of superfoods, but they should be."
Again, it is important that you cook mushrooms thoroughly, and not simply in order to break down small amounts of natural toxins.
"The cell walls of mushrooms are tough, making it difficult for the digestive system to get to all the nutrients inside them," Weil writes. "Mushrooms often contain chemical compounds that can interfere with digestion and nutrient absorption -- sufficient cooking breaks down the tough cell walls, inactivates the anti-digestive elements, and destroys many toxins. It also makes mushrooms taste much better."
Mushrooms at the Store, the Farmers Market, and in the Wild
When shopping for fresh mushrooms, look for ones that are unspotted and free of slime. Nolan says that the nutritional content of mushrooms can vary greatly depending on where they are grown.
Supermarkets source their produce from a variety of sellers, so the mushrooms available this week may be from a different area as those offered last week. She advises her clients to shop at farmers markets when they can, buying from the same farmers each time. That way, they'll know they come from the same soil each time.
Some people may prefer to find their own mushrooms out in the wilderness.
"Foraging is definitely more popular these days," says 'Wildman' Steve Brill, who has been leading groups on gathering trips throughout New York State and the Northeast for nearly 30 years.
Brill credits the Internet, which has allowed information sharing among enthusiasts to flourish and spread. Yahoo groups, like Forage Ahead and NortheastMushrooms, as well as Facebook pages and meetup.com groups have brought people together to discuss and hunt their favorite mushrooms.
Foraging is not without risks -- there are, of course, poisonous, even deadly mushrooms. The North American Mycological Association, which has been tracking mushroom poisonings for more than 30 years, receives an average of one report of a human death due to mushrooms each year. However, in 2009, there were four people who died after eating mushrooms containing a toxin called amatoxin, according to the North American Mycological Association.
Brill says that foraging intelligently will keep trouble at bay.
"You have to make an effort to mess up with mushrooms, and it's usually people who have no knowledge who do so," Brill says. “A lot of the fear is simply nature-phobia.”
Brill says that touching poisonous mushrooms is not dangerous, but he strongly advises only eating mushrooms that can be identified with 100% certainty -- and none should be eaten raw.
Finally, there are mushrooms that are eaten not for their nutritional content but for their psychedelic properties. Often called magic mushrooms, these fungi contain a hallucinogenic substance called psilocybin.
In one such study, published in the Journal of Psychopharmacology, researchers at Johns Hopkins report that a single dose of psilocybin -- given in a research study that was closely supervised -- led to a long-lasting increase in openness, a personality trait related to imagination, creativity, feelings, and abstract ideas. The study authors suggest that psilocybin may prove useful in treating neuroticism and accompanying depression and anxiety, but it will take more research to learn how that works.
Psilocybin, however, is illegal. The Drug Enforcement Administration (DEA) classifies it as a Schedule 1 substance, meaning it has a high potential for abuse and no accepted medical use in the U.S. Unless and until that changes, it is recommended that you only seek out mushrooms meant to be savored for their flavor and health benefits. There are plenty to choose from, and plenty of ways to prepare them. Here's what Weil likes to do:
"When I try a new species for the first time, I usually sauté it in a little olive or grapeseed oil to experience its flavor and texture," he says. "Many thick-fleshed mushrooms can be grilled over charcoal and basted with a low- or nonfat sauce. In addition to grilling, simmering in broth and stir-frying with vegetables are great ways to prepare a delicious meal with mushrooms."