This sleep aid isn’t a dream for everyone

Half of all Americans experience occasional or chronic sleep problems, leading to recent research on the role of the hormone melatonin in the body’s sleep cycles -- and consumer demand for synthetic melatonin supplements. But many unknowns remain about their use.

Uses: Primarily to fight insomnia or jet lag, but studies on its effectiveness have been mixed.

Dose: Experts typically recommend a low dose (0.1 to 0.3 milligrams), with increases as needed. For jet lag, a typical dose is 3 milligrams before a flight and 1.5 milligrams after landing and before going to bed.

Precautions: Pregnant women and women taking birth control pills or hormone replacement therapy should not take melatonin because it can interfere with natural hormone levels. People taking antidepressants should also avoid melatonin because it could create a serious drug interaction. Some research suggests melatonin can raise blood pressure. As a treatment for insomnia, it could lead to next-day side effects, such as grogginess.

Research: Melatonin has been promoted as an anti-aging agent because the amounts produced by the body decrease with age. But there is little research in humans to support this claim. The National Cancer Institute is sponsoring a study exploring whether melatonin supplements can make brain tumor cells more sensitive to radiation while protecting normal cells from damage.

Dietary supplement makers are not required by the U.S. government to demonstrate that their products are safe or effective. Ask your health-care provider for advice on selecting a brand.