According to the American Cancer Society, although some wheatgrass champions claim it can "shrink" cancer tumors, "available scientific evidence does not support the idea that wheatgrass or the wheatgrass diet can cure or prevent disease".[103] Wild yam (or Chinese yam) – types of yam, the roots of which are made into creams and dietary supplements that are promoted for a variety of medicinal purposes, including cancer prevention. The American Cancer Society says of these products, "available scientific evidence does not support claims that they are safe or effective."[104]