Shiitake mushrooms contain polysaccharides, including lentinan and other beta-glucans. People take powdered or extracted shiitake with food or on its own to help maintain normal immune defenses and protect the cardiovascular system.
Eat only cooked shiitake. Raw mushrooms can trigger shiitake dermatitis, an uncommon but uncomfortable skin rash. Anyone allergic to mushrooms should avoid shiitake entirely. The high purine content may also cause problems for people managing gout. Stop use and check with a doctor if you notice skin irritation or joint discomfort.