Probiotics are live microorganisms, predominantly bacteria, but can also include yeasts, which, when administered in adequate amounts, confer a health benefit on the host. Many probiotic yeasts, such as Saccharomyces boulardii, are effective. They are known to aid in the digestion of complex carbohydrates and lactose (milk sugar) by producing enzymes like lactase, which helps individuals with lactose intolerance. While some of these organisms are found in fermented foods, they can also be present naturally in the human gut microbiome.