Button mushroom (Agaricus bisporus) is the most widely eaten mushroom worldwide. Supplement forms include powder, extract, and dried preparations. They supply B vitamins, selenium, and beta-glucans.
People take it mainly to support immune function. The beta-glucans in the mushroom work to modulate immune activity. Others use it for general wellness and antioxidant support, though the body of evidence is thinner than for medicinal mushrooms like reishi or shiitake.
Take button mushroom supplements with meals. Dosing depends on the form, so follow the label. The mushroom is safe for most people. Avoid it if you have a mushroom allergy. Speak with a healthcare professional before use if you are pregnant, nursing, or taking medications.