In summary, evaluation of the nutrient composition of fermented dairy foods indicates that, like milk, they are good sources of protein, calcium, riboflavin and vitamin B12. Fermented dairy foods are also a good source of folic acid due to microbial synthesis. The absorption of lactose in yogurt is enhanced by the presence of bacterial lactase. Like their nonfermented counterparts, fermented dairy foods may be chosen within a broad range of fat and calorie levels. Fermented and low fat milk products contain only forty to sixty-three calories per 100 grams, whereas sour cream, like sweet cream, is high in fat and contains over two hundred calories per 100 grams. Some fermented dairy foods have antibiotic or antitumor activity in vitro or in laboratory rats. The relevance of these findings to the treatment of human diseases is unknown.