They are different strains with different effects. Here is a very good explanation. Excerpt: “How To Compare Probiotic Supplements With so many probiotics on the market today, it is becoming more and more difficult for people to decide on which one to try. Here are some suggestions to help you make an informed decision. Look for a probiotic with at least 15 living strains of beneficial microbes. Products containing probiotic “metabolites” rather than living microorganisms are not the same. Many products (such as yogurt) only contain one to three strains of live bacteria. Each strain of bacteria contributes a different role and works in harmony with the other strains. When only a few strains are present, the resulting health benefits are not complete. Here are examples of roles of different strains of beneficial bacteria in the Lactobacillus family: * Stimulates the immune sytem: L. acidophilus, L. casei, L. planetarum, L. delbruekii, L. bifidus* * Possesses anti-tumor activity: L. acidophilus, L. casei, L. planetarum, L. delbruekii, L. bulgaricus, L. helveticus, L. lactis* * Protects from acute diarrhea: L. bulgaricus, L. acidophilus, L. bifidus, L. casei * Improves lactose tolerance: L. bulgaricus, L. bifidus, L. acidophilus, L. sporogenes * Lowers blood cholesterol levels: L. acidophilus, L. sporogenes, L. bifidus * Aids in nutrient absorption and elimination of toxins: L. planetarum * Protects from candida yeast: L. planetarum * Protects from antibiotic-associated diarrhea: L. acidophilus, L. bulgaricus, * Protects from Listeria infections: L. casei, L. lactis * Protects from Leaky Gut Syndrome: L. brevis * Improves Inflammatory Bowel Syndrome (IBS): L. sporogenes * Protects from harmful bacteria: L. lactis, L. bulgaricus, L. acidophilus, L. sporogenes * Protects from vaginal yeast infections: L. fermenti, L. acidophilus, L. bifidus * Lowers blood pressure and increases bone density: L. helveticus * Synthesizes B vitamins: L. lactis, L. bifidus, L. acidophilus”