The dead yeast cells of brewer's yeast (Saccharomyces cerevisiae) is used as a dietary supplement to enhance milk production. No scientifically valid studies in humans have been performed that establish any effect of brewer's yeast on milk supply. Although studies in ruminants indicate that brewer's yeast might increase milk supply, the effect is attributed to improved nutrition (increases in vitamin B and chromium) rather than any specific effect on lactation. Some side effects, mostly gastrointestinal, have been reported by nursing mothers taking brewer's yeast. There are wide variations in the content of brewer's yeast products. In a US survey, of 190 mothers who used brewer’s yeast as a galactogogue 46% thought it increased milk supply.