S-adenosyl-L-methionine (SAMe or AdoMet) is a commonly used nutritional supplement available in the United States since 1999. SAMe is metabolized to homocysteine, a known cardiovascular risk factor. No study has determined the effect exogenous SAMe administration has on the long-term levels of homocysteine in humans. As a nutritional supplement, SAMe is not regulated by the Food and Drug Administration, despite being used to treat clinical diseases such as depression and osteoarthritis.