For thousands of years, Cordyceps has been highly valued in China as a tonic food and herbal medicine. Until recently, it was only available in nature as it grows in the body of a caterpillar. Thus, the fungus was rare, very expensive, and subject to contamination. Today, a potent strain of Cordyceps, CS-4, is grown in a liquid broth medium under sterile conditions, making it safe, affordable, and available for use as nutritional therapy for many conditions. As with the other medicinal mushrooms, effects of Cordyceps appear to come from its polysaccharides, as well as its sterols, lipids, nucleosides and especially in the de-oxy nucleosides, which have been found in no other source in nature. Many studies have shown this mushroom’s ability to stimulate and modulate the immune system and increase red blood cells. As an immune modulator and adaptogen, Cordyceps was shown to boost depressed immune function, but not enhance a normally functioning immune system to the same degree.