Align contains probiotic bacteria, similar to those in the active cultures of yogurt or fermented milk products. However, yogurt in the United States is not required to contain any live cultures, and tests have shown that some yogurt products have a wide range of levels of live bacteria. The delivery of probiotics in either yogurt or fermented milk is limited by the need for cold storage and an associated shorter shelf life. Additionally, many people may have trouble consuming sufficiently large quantities of these products.