Beneficial bacteria present in fermented dairy foods—namely live culture yogurt—have been used as a folk remedy for hundreds, if not thousands, of years. Yogurt is the traditional source of beneficial bacteria. However, different brands of yogurt can vary greatly in their bacteria strain and potency. Some (particularly frozen) yogurts do not contain any live bacteria. Supplements in powder, liquid extract, capsule, or tablet form containing beneficial bacteria are other sources of probiotics.