Mushrooms
For centuries, people around the world have turned to mushrooms for a healthy immune system. Contemporary researchers now know why. Studies show that mushrooms increase the production and activity of white blood cells, making them more aggressive. This is a good thing when you have an infection.
Shiitake, maitake, chaga, and reishi mushrooms appear to pack the biggest immunity punch. Experts recommend eating a quarter ounce to an ounce a few times a day for maximum immune benefits.