In cold and flu season, it is important to eat a balanced diet, including foods that can naturally maintain the immune system. While the science on mushrooms and immunity continues to evolve, we already know mushrooms offer a variety of nutrients associated with immunity. Popular mushroom varieties are a rich source of selenium, a mineral that works as an antioxidant critical for the immune system; and also have ergothioneine, an antioxidant that may help protect the body’s cells.