Discovered about 45 years ago, melatonin is a hormone that is produced in humans by our pea-sized pineal gland located in our brain just above the cerebellum. Melatonin is classified as a hormone because it has widespread effects in the body.

Melatonin is released into our bloodstream during darkness. During daylight hours, melatonin levels are barely detectable. Light exposure to our retinas is transmitted to the pineal gland to switch the gland on or off. Even a brief exposure to bright light in the middle of the night can decrease the melatonin surge.

Melatonin has effects on reproduction and sleep-wake cycles. For instance, in hamsters, the length of daylight reduces melatonin levels which then effect reproductive organs, stimulating such things as sperm production. Melatonin is used to artificially control seasonal reproduction in sheep and can increase the breeding cycle to two per year instead of just one. In humans, melatonin influences the timing and release of female reproductive hormones, affecting menstrual cycles, menarche, and menopause.

Most studies have shown that melatonin production is high in children, falls during puberty, and then declines steadily with age and is barely detectable in older adults. About 50 percent of adults over 65 complain of sleep disorders. It has been postulated that a lower production of melatonin may be implicated in older adult sleep difficulties.

A 2001 study showed that the sleep efficiency of people over age 50 who had a sleep disorder improved with doses of .1 mg, .3 mg and 3.0 mg of melatonin 30 minutes before bedtime. The .3mg dose was considered the most physiologic, since it elevated plasma melatonin levels only to normal. The 3.0 mg dose improved sleep but melatonin levels remained raised into the daylight hours of the next day (not normal for naturally-produced melatonin). Other studies have confirmed that melatonin is effective in promoting sleep initiation and sleep maintenance in older insomniac adults.

It is likely that the most natural dosage of melatonin for sleep enhancement is .3 mg to 1.0 mg. Melatonin does not adversely affect the sleep patterns of people who have no sleep disorder. Similar doses have been used to study melatonin's effects on nocturnal blood pressure and on cognitive abilities in older adults. In the blood pressure study, which was limited to 16 men of various ages with essential hypertension, blood pressure was lowered by 5-10 millimeters of mercury. In the older adult cognitive performance study, recall was improved.

Since it is a hormone with widespread effects, many doctors feel that the moderate positive effects of melatonin are not worth the risk of potential long-term side effects. However, there have been no documented long-term adverse effects. Ingesting melatonin does not appear to decrease the pineal gland's ability to produce melatonin on its own.

It is my opinion that 1 mg of melatonin taken at night by people over the age of 55 will most likely benefit their wellness. I don't recommend long-term use in younger adults or children. Since you are 45 years old, I would recommend only short-term or occasional use of melatonin. The major benefit of melatonin is the maintenance of a proper circadian rhythm which appears to have positive effects on sleep, blood pressure and cognitive abilities.