Nitric oxide is a messenger chemical used by the body to relax blood vessels and has therefore been studied for its potential to treat angina and high blood pressure. One way to increase levels in the body is through the administration of the amino acid arginine. But so far, the appropriate amounts for ingestion have not been determined. Nevertheless products containing arginine are being promoted to the public for the “treatment and prevention” of heart disease. They are supposed to be used “under the advice of a physician,” but are available over the counter so there is no control over their use.