Kefir Grains are a symbiotic culture of bacteria and yeast. Think of these grains as a town filled with different kinds of proteins, lipids, polysaccharides, a big set of bacteria and yeasts all living together harmoniously. They feed on simple sugars and multiply in millions.Kefir contains millions of probiotics, which are bacteria with potential health benefits. It's also low in lactose and packed with vitamins and minerals that are good for your body. Scientists have found a range of possible health benefits of kefir, including improved cholesterol, blood sugar control, and gut health.