Melatonin: What Is It?

This hormone is made by the pineal gland, a structure in the brain. Contrary to the claims of some, secretion of melatonin does not necessarily decrease with age. Instead, a number of factors, including light and many common medications, can affect melatonin secretion in people of any age.

Melatonin supplements can be bought without a prescription. Some people claim that melatonin is an anti-aging remedy, a sleep remedy, and an antioxidant (antioxidants protect against free radicals, which are naturally occurring oxygen-related molecules that cause damage to the body). Early test-tube studies suggested that, in large doses, melatonin might be effective against free radicals. However, cells produce antioxidants naturally, and in test-tube experiments, cells reduce the amount they make when they are exposed to additional antioxidants.

Claims that melatonin can slow or reverse aging are very far from proven. Studies of melatonin have been much too limited to support these claims and have focused on animals, not people.
Research on sleep shows that melatonin plays a role in our daily sleep/wake cycle, and that supplements, in amounts ranging from 0.1 to 0.5 milligrams, can improve sleep in some cases. If melatonin is taken at the wrong time, though, it can disrupt the sleep/wake cycle. Other side effects may include confusion, drowsiness, and headache the next morning. Animal studies suggest that melatonin may cause some blood vessels to constrict, a condition that could be dangerous for people with high blood pressure or other cardiovascular problems.

These side effects are important to keep in mind since the dose of melatonin usually sold in stores—3 milligrams—can result in amounts in the blood from 10 to 40 times higher than normal. What long-term effects such high concentrations of melatonin may have on the body are still unknown. Until researchers find out more, caution is advised.

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