As Vegnuary, the initiative to promote plant-based diet, is ongoing, it's a good time to remember mushrooms and their health benefits. Although mushrooms are considered vegetables (that’s why they are great for Vegnuary), they are technically not plants: they are a type of fungus that contains ergosterol, a substance similar in structure to cholesterol in animals.

There are 10,000 known types of mushrooms each of them having their health benefits. But we will discuss general ones — from being low in calories and fat to containing fiber, various nutrients as well as non-nutritive plant substances such as polysaccharides, indoles, polyphenols, and carotenoids. All these features make mushrooms a great dish.

Under the cap

Mushrooms are source of:

• B vitamins (B2, B3, folate, B5)
• Phosphorus
• Vitamin D
• Selenium
• Copper
• Potassium (1)

Addition of a serving (84 g) of mushrooms to the diet increases dietary fiber (5%–6%), copper (24%–32%), phosphorus (6%), potassium (12%–14%), selenium (13%–14%), zinc (5%–6%), riboflavin (13%–15%), niacin (13%–14%), and choline (5%–6%) in both adolescents and adults. It also increases iron (2.32%), thiamin (4.07%), folate (3.66%), and vitamin B6 (4.64%) in adults only, but has no impact on energy, carbohydrate, fat, or sodium. (2)

Multiplying vitamin D

Most mushrooms sold in supermarkets are grown in the dark so they contain little if any vitamin D. But the use of ultraviolet (UV) light during production or even after harvesting — either by natural sunlight or a UV lamp — increases their content of vitamin D. Then ergosterol produces vitamin D2 (ergocalciferol), a form found only in plants. The other main form of vitamin D is D3 (cholecalciferol) found in animal foods (egg yolks, oily fish). (1)

The amount of vitamin D mushrooms contain varies and depends on how long the mushrooms are exposed to UV light. For example, wild mushrooms such as chanterelles and morels can contain up to 1200 IU of vitamin D per 3.5-ounce serving. Mushrooms grown in darkened conditions like white button, shiitake, and oyster contain less than 40 IU. (1)

Health benefits

Mushrooms do contain components that may exert antioxidant, anti-inflammatory, and anticancer effects, but the exact mechanism is an area of active research. Here are some of the already known benefits:

• Mushrooms contain polysaccharides that act as a prebiotic. Studies show that they lead to the growth and survival of beneficial strains like Lactobacillus and Bifidobacterium. (1)
• Such bioactive molecules that mushrooms contain like polysaccharides, terpenoids, proteins and polyphenols which enhance the immune strength, lower and prevent risks of cancers, protect the nervous system from the damage of aging etc. (3)
• According to research, men who consumed mushrooms once or twice a week — an average of about 3 ounces per serving — had an 8% lower risk of prostate cancer compared with those who ate no mushrooms. And among men who ate mushrooms 3+ times per week, risk was 17% lower. What is more, this link is traced regardless of the men's intake of other vegetables and fruit or how much meat and dairy they consumed. (4)
• One study shows that there is a link between eating more than 300 grams of mushrooms weekly and reduced risk of developing mild cognitive impairment, or MCI (a condition characterized by poor memory and language difficulties that aren’t yet impairing daily functioning). (5)