Television commercials often tell us about the benefits of active yogurt cultures, or specific living bacteria, to our digestive system and overall health. two bacteria cultures, lactobacillus bulgaricus and streptococcus thermophilus, convert pasteurized milk to yogurt by fermentation. all yogurts are required to be made with these two cultures. in addition, some yogurts contain lactobacillus acidophilus, bifidu. some health food advocates claim that some yogurts may have no active cultures. if the label says "made with active cultures," are we always getting the benefits of active bacterial cultures?