Though mushrooms are commonly considered vegetables, they are actually in a category separate from plants. They’re fungi. Unlike plants, they don’t have any roots or leaves, they don’t flower or bear seeds, and they don’t need light to grow (though some do need light to start its fruiting stage). Instead mushrooms proliferate in the dark and reproduce by releasing billions of spores.
Mushrooms have a long and esteemed history. The Chinese used them for medicine, and the Egyptian pharaohs were so enamored of them that they decreed them a royal food. The French, however, took the passion for mushrooms to a new level, being the first to cultivate them in caves, beginning in the 17th century. By the late 1800s, mushrooms were being grown on a commercial scale in other European countries, as well as in the United States, where farmers in Pennsylvania eventually developed new methods for growing them indoors.
While some mushrooms are still cultivated in caves or cellars, today most are grown year round in specially designed buildings in which all aspects of the environment—light, temperature, humidity, and ventilation—can be controlled. As a result, cultivated versions of wild mushrooms, which were once considered an expensive delicacy, are now affordable and widely available.
Because they lack the brighter colors of so many other vegetables, mushrooms are not usually thought of as a nutritionally beneficial food. In truth, mushrooms actually do supply some key nutrients: The B vitamins niacin and riboflavin, as well as some B6 and folate. They also provide iron, potassium, and selenium. Mushrooms are also low in calories—one cup of raw mushrooms has about 20 calories. They are a good source of dietary fiber and, surprisingly, often vitamin D (if they have been exposed to sunlight).
Mushrooms partially owe their flavor to glutamic acid, a natural version of the flavor enhancer monosodium glutamate (MSG). However, while monosodium glutamate contains sodium, fresh mushrooms are virtually sodium free. Glutamate (the non-acid portion of glutamic acid) is the sole member of one of the two biochemical groups responsible for the taste of umami (savory). The other group consists of ribonucleosides, specifically inosinate and guanylate. Some mushrooms—notably shiitake and porcini—also have high levels of ribonucleosides. The effect of the two groups on umami is synergistic.
For a full listing of nutrients, check these varieties of mushrooms in the National Nutrient Database:
- Button (white) mushrooms
- Chanterelle mushrooms
- Morel mushrooms
- Oyster mushrooms
- Portobello mushrooms
- Shitake mushrooms
It may be tempting to eat mushrooms you have picked yourself in the wild. But beware: They could be highly toxic. Of the 38,000 varieties of mushrooms, some are edible, but others are deadly.
Indeed, some wild mushrooms bear such a striking resemblance to edible mushrooms that they occasionally fool even the most experienced mushroom forager. Most victims of life-threatening mushroom poisoning in North America are people who mistake Death Caps (Amanita phalloides) for edible Paddy Straw (Volvariella volvacea) mushrooms. It’s best to leave foraging for wild mushrooms to the experts and gather your own from the market instead.
Button, shiitake, oyster, and enoki mushrooms are available all year. Other specialty varieties are on the market more sporadically, with supplies best in summer and fall. Pennsylvania grows much of the domestic crop; California, Oregon, Washington State, Florida, and Michigan are also leading suppliers. Dried mushrooms, naturally, are available year round. Some, like the wood ear, are mainly sold in Asian markets.
How to choose the best mushrooms
For common cultivated mushrooms such as button and cremini, choose those that have a firm texture and even color. Reject any that appear slimy, bruised, or pitted. Also look for mushrooms with closed “veils”—the area where the cap meets the stem: A wide-open veil indicates that the mushroom has aged and will have a shorter storage life.
If you’re not fussy about appearance, slightly older mushrooms—which actually have a richer flavor—may be bought for immediate use. To minimize waste in recipes that call for caps only, choose mushrooms with short stems.
Fresh specialty mushrooms will not have the clean, uniform appearance of cultivated mushrooms. They should, however, be firm and meaty, as well as dry to the touch but not withered. Even uncooked, they should have a pleasant, earthy fragrance.
Published April 20, 2016