Probiotic 55 Billion is formulated with 10 strains of viable organisms, including 11 billion Bifidobacterium CFUs and 44 billion Lactobacillus CFUs , the bacteria most dominantly found in the large and small intestines. Since intestinal flora often decreases with age, taking a probiotic can help your body maintain a healthy functioning digestive system. Plus, we use special delayed release capsules that are optimized to help prevent probiotics from being damaged by stomach acid, allowing them to reach the small intestine for maximum effectiveness.