The best probiotics in supplement form contain at least 20 billion bacteria, according to WebMD. However, nutritionists prefer getting probiotics from natural food sources such as yogurt and kefir whenever possible.
Probiotics are the live bacteria that keep the gut running smoothly. The supplements come in many forms, including pills, gummies, powders and drinks. There are several strains of probiotics, and each claims unique benefits. For example, strains of lactobacillus have been touted to help with lactose problems in the gut, and bifidobacterium lactis enhances the immune system in some people, according to WebMD.
Probiotics also occur in some other fermented foods such as kimchi, some cheeses and sauerkraut, says WebMD. The nutrition labels on foods containing probiotics typically mention it or say that they contain live, active cultures.