Some experts say that the "friendly" bacteria found in foods such as yogurt may improve digestion and ease symptoms of allergies, irritable bowel syndrome, and lactose intolerance. But they also say that not all probiotics are created equal. Just like the foods they are found in, probiotics can expire, and the number of microbes are also important, says dietitian Paula Wagler. In this article, Wagler discusses who might benefit from probiotics, and she offers information on where the best...