They are popular both as a food and a medicinal herb. They have long been believed to increase energy, cure colds , and eliminate intestinal worms.
Shiitake mushrooms contain fats, carbohydrates, proteins, fiber, vitamins, and minerals.
Their key component, however, is a polysaccharide called lentinan. Lentinan is extracted from the powdered mycelium of the mushroom, and is rich in polysaccharides and lignans. Shiitake mushroom formulations, made from the powdered mycelium that appears before the mushroom cap and stem grow, may make hepatitis B less infectious. Shiitake mushrooms stimulate white blood cells to produce interferon. They appear to help increase immunity in laboratory studies.