OptiBac Probiotics 'Saccharomyces boulardii' is an extensively researched microorganism, proven to reach the gut alive. for anyone, 1 year and over, seeking a pure Saccharomyces boulardii supplement. Each capsule provides 5 billion live cultures of pure, shelf stable Saccharomyces boulardii. This strain has been internationally acclaimed as a well-researched and unique microorganism, and has been safely used for the last 50 years. Saccharomyces boulardii is a natural food supplement, and not a medicine. Saccharomyces boulardii is a unique microorganism which is sold widely in the US, Scandinavia, Germany & France. This microorganism is more robust to environmental stressors than more common bacterial live cultures, and shows strong resistance to heat, humidity and stomach acidity levels. These live cultures of S. boulardii have been tested and shown to be especially stable and resistant.