Second, it can reset your body clock, either forward or back, to help you adapt to a new time zone. When you take melatonin in the afternoon, it tends to advance the body clock. Because of these effects, melatonin has been studied as a sleep aid for shift workers, including those who rotate between day and night shifts. Most of us find it hard to stay alert at night, even if we sleep during the day. The question of whether melatonin can help shift workers is not an easy one to answer, says Dr. Zhdanova.
Individuals respond differently to melatonin .
Even if they time it to help them adjust to new work schedules, it may actually make some workers more groggy and less alert as they move from a day shift to a night shift, then back again. There s little evidence to support either of these claims, says Richard L. Sprott, Ph.D., executive director of the Ellison Medical Foundation, an organization that funds research on the biology of aging, in Bethesda, Maryland. Animal studies indicate that declining levels of melatonin may be associated with accelerated aging, but that decline could be a result, not a cause. There is some evidence that melatonin may inhibit tumor growth, at least in animals. Research on the effects of melatonin on tumor growth in humans is conflicting, but most reports do show some kind of protective action.