Red yeast rice has been used in China for centuries as both a food and as a medicinal substance. It is made by fermenting a type of yeast called Monascus purpureus over red rice. In Chinese medicine, red yeast rice is used to promote blood circulation, soothe upset stomach, and invigorate the function of the spleen, a body organ that destroys old blood cells and filters foreign substances. In addition, this dietary supplement has been used traditionally for bruised muscles, hangovers, indigestion, and colic in infants. Recently, it has been discovered that red yeast rice contains substances that are similar to prescription medications that lower cholesterol. There is also growing interest in evaluating red yeast rice for use as a natural food dye and/or preservative.