Agricultural Research Service scientist David Brewer discovered through research that shiitake mushrooms contain a high-molecular-weight polysaccharide (HMWP) that can enhance the human immune system. David Brewer found that shiitake mushrooms have this effect after conducting experiments on a small farm in Arkansas.
Other studies have shown that another compound in shiitake mushrooms—eriadenine (also known as erythadenine)—can lower cholesterol levels.
The antioxidant content of shiitake mushrooms is 12 times that of malt and 4 times that of chicken liver. Compared to matsutake mushrooms and Maitake (also known as Grifola frondosa, commonly known as cloud mushroom, chestnut mushroom, or lotus mushroom), its effects on lowering blood pressure and resisting cancer are stronger.