Thirty million Americans are lactose intolerant, meaning their bodies don't produce enough lactase, the enzyme needed to digest lactose, the natural sugar found in milk and other dairy products. Common symptoms of lactose intolerance include nausea, cramps, bloating, gas, and diarrhea, which may begin about 30 minutes to 2 hours after eating or drinking foods that contain lactose. Fermented milk products, such as yogurt, containing L. bulgaricus and S. thermophilus can help decrease the symptoms of lactose intolerance, because the probiotic cultures they contain reduce lactose content by "predigesting" some of the milk sugar, metabolizing it to lactic acid and by providing additional lactase enzyme activity.