Calories in Mushrooms, white button

What makes mushrooms so powerful?

White button mushrooms (Agaricus bisporus) share their exact species with cremini and portobello mushrooms; the only difference is age and a genetic mutation that prevents brown pigmentation. What is less known is their unique ability to produce vitamin D2 (ergocalciferol) when exposed to UV light. Like humans, these fungi possess ergosterol in their cell membranes. When commercial mushrooms are deliberately exposed to UV-B light post-harvest, their vitamin D2 levels can skyrocket from negligible amounts to substantial quantities. Furthermore, white button mushrooms contain notable amounts of ergothioneine and glutathione, two important antioxidant compounds that remain remarkably stable even after cooking. Unlike most plants, mushrooms have cell walls made of chitin—the same indigestible structural polysaccharide found in the exoskeletons of insects and crustaceans—rather than cellulose. This chitin is what gives mushrooms their structural integrity and contributes to their meaty texture, while also acting as a source of insoluble dietary fiber that survives the cooking process intact.