Sauerkraut is finely cut raw cabbage that has been fermented by various lactic acid bacteria. It has a long shelf life and a distinctive sour flavor, both of which result from the lactic acid formed when the bacteria ferment the sugars in the cabbage leaves. Sauerkraut is incredibly nutritious and healthy. It provides probiotics and vitamin K2, which are known for their health benefits, and many other nutrients. Eating sauerkraut may help strengthen your immune system, improve your digestion, reduce your risk of certain diseases, and even lose weight.