26 May 1999

Supplement May Cause Unwanted Reactions In The Body

People who take the popular supplement melatonin hoping for antioxidant or sleep benefits may be getting more than they bargain for, according to Louisiana State University chemists. Their newly released findings show melatonin reacts with chemicals in the body to form compounds that could alter behavior.

Details about the research will appear in the peer-reviewed journal Chemical Research in Toxicology, published by the American Chemical Society (ACS), the world's largest scientific society. The paper will become available on the ACS Web May 26 and is tentatively scheduled to be in the journal's June 14 print edition.

Melatonin is produced naturally by the body to control sleep cycles, but is needed in only very low concentrations. It is sold as a sleeping aid and as an antioxidant. However, chemists William A. Pryor and Giuseppe L. Squadrito of the university's Biodynamics Institute say that the antioxidant properties of melatonin are very modest at best and that metabolizing excess melatonin may cause more harm than good. "It is our hypothesis," says Squadrito, "that secondary products of melatonin have as yet unrecognized health effects."

The scientists found that carbonate and nitrogen dioxide radicals, which are constantly formed in the human body from peroxynitrite, react with melatonin to form two cyclic metabolites that resemble brain signaling chemicals but whose biological function is unknown. "Our kinetic modeling, using competitive reactions, indicate that the reaction of melatonin with peroxynitrite-derived free radicals is physiologically important," states Squadrito adding that it "becomes even more important when taking melatonin as a supplement."

While admitting that it is unclear how increased amounts of the neurotransmitter-like metabolites impact health, Squadrito theorizes that "they could have an important effect on aspects of behavior...like mood." All of these experiments were conducted within laboratory equipment. Squadrito says future studies are needed to measure the compounds within the human body and determine whether there is a correlation between their levels and any health problems.