Having a healthy immune system starts with a healthy gut. Backed by 20 years of clinical research, Nature?s Bounty Ultra Strength? Probiotic 10 is now in a one per day formula with 20 billion live probiotic cultures. It contains 10 distinct probiotic strains to supplement the natural diversity of your digestive ecosystem. The GI microbiome is active in the digestion of food and absorption of nutrients and also supports tissues lining the immune system. The unique strains in Probiotic 10 help the body?s natural digestive process, contribute to immune health and even upper respiratory function. Nature?s Bounty Ultra Strength Probiotic 10 one-a-day probiotic for adults provides its health benefits at 20 billion CFU per day and is guaranteed through expiration.