Melatonin: Hormone of Sleep and Much More


This versatile hormone affects every system of the body.


By Earl Mindell, R.Ph., Ph.D. and Melissa Block

New research shows this hormone is much more than a sleep aid. When darkness falls at day’s end, the hormone melatonin is made in the pea-sized pineal gland located in the part of the brain right behind the center of the brow. This hormone is best-known for making you sleepy, but it has many other functions, including regulation of immune, digestive, thyroid and reproductive functions. It even works to control the onset of puberty. Melatonin is ubiquitous in life on planet earth; it even exists in protozoa, and has been around for approximately a billion years. Melatonin production rises as soon as light wanes, and peaks between the hours of 12:00 midnight and 2:00 a.m.

The pineal gland is considered today to be one of the most important organs in the endocrine (hormonal) system. It acts as a biological clock, telling the body when it’s night and when it’s day, and triggering the production of specific hormones accordingly. Specialized photoreceptors in the eyes are thought to trigger most melatonin secretion. (Some melatonin is also made along the walls of the gastrointestinal tract and in the retinas of the eyes.)

Melatonin production naturally decreases with passing years. By the age of 60, we produce half of what we did at 20.

The pineal gland’s production of melatonin may also be one key to understanding the aging process. Melatonin production naturally decreases with passing years. By the age of 60, we produce half of what we did at 20.

For the past 30 years, melatonin has been the subject of intensive research. A natural and therefore unpatentable substance, it remains controversial because drug companies won’t study it; without a patent, they don’t make the huge profits. Still, the word is out about melatonin, and it’s being used by millions of people who want to naturally improve their sleep quality or their general state of health.

Melatonin for Sleep Problems
Most of the research on this versatile hormone deals with its potential usefulness as a sleep aid. The National Institutes of Health has put millions of dollars towards sleep research involving melatonin. In one of the most recent studies on this subject, published in the October 2001 issue of Journal of Clinical Endocrinology and Metabolism, researchers found that only 0.3 mg of melatonin, taken a half-hour before bedtime, was enough to restore efficient sleep in people over age 50 with sleep disorders.

Melatonin, along with the use of bright light therapy, has also helped to shift sleep time in people with delayed or advanced sleep phase syndromes (DSPS or ASPS) [people who wake up very late or very early]. Taking melatonin at the desired bedtime and being exposed to bright light in the mornings has been shown to gradually shift the body’s internal clock to a more socially acceptable pattern.

Other Possible Benefits of Supplemental Melatonin
Supplemental melatonin has been used to treat and prevent anxiety, depression, and sleep problems related to autism. High-dose melatonin shows promise as a treatment for cancer and AIDS. Low doses have been shown to lengthen the lives of lab animals by as much as 30 percent. Some evidence exists that it could be helpful for those with Parkinson’s disease and Alzheimer’s disease.

When researchers set out to discover the highest safe dose of melatonin, they gave higher and higher doses to rats. They found that no dose was high enough to kill the animals. Humans have taken doses of up to 6,000 mg at a time without side effects aside from sleepiness the following day. However, since rats are nocturnal creatures, we can’t make too many assumptions about humans and melatonin based on rat studies, and I don’t advise taking high doses.

Melatonin vs. carcinogens. In research by melatonin expert Russel J. Reiter, animals were given a dose of a poison called safrole. Safrole does serious damage to the DNA of liver cells, predisposing them to cancer. When a tiny amount of melatonin was given as well, only 41 percent of the damage was seen compared to animals given no melatonin. With a larger dose, only one percent of the damage was seen. Other research by Dr. Reiter found that when supplemental melatonin was given to one group of animals exposed to normally lethal doses of radiation, only half the number of animals died compared to the group that didn’t get melatonin.

Dozens of studies showing melatonin’s anti-carcinogenic effects have been published. Melatonin appears to forestall cancer growth, and some studies in humans have shown that late-stage cancer patients benefit from high-dose (5 to 10 mg a day) melatonin. Mainstream scientists protest that it hasn’t been sufficiently studied as a cancer treatment, but I’d venture to say that it’s been studied as much as or more than a lot of the chemotherapy agents.

The antioxidant power of melatonin. Melatonin helps protect cells against free radical attack, on a par with vitamin E and glutathione. It stimulates production of the antioxidant enzyme glutathione peroxidase.

Melatonin and zinc. Research has shown that when melatonin is supplemented in people with low levels of the mineral zinc, their zinc levels normalize. This has led some scientists to believe that the presence of melatonin in the GI tract may have something to do with efficient mineral absorption.

Melatonin and depression. Melatonin levels have been found to be low in some forms of chronic depression, bipolar disorder (manic-depression), and in chronic schizophrenia. In people with seasonal depression—caused by short days and long nights—melatonin at night and bright light in the daytime has been shown to effectively improve symptoms.

Melatonin for headache. Studies have found that melatonin is low in migraine headache sufferers, and that administering melatonin during migraine attacks relieved pain and decreased headache recurrence.

Melatonin and immunity. Melatonin promotes the health of the thymusgland, an important component of the immune system that tends to deteriorate with age. Studies by Italian researchers show that melatonin supplements can improve immunity in the face of advancing age and stress.

Melatonin for autistic or developmentally disabled children.Kids with autism, Down syndrome or other developmental disabilities seem to benefit from melatonin supplementation. Many of these children have severe sleep problems, and regulating their sleep patterns helps them (and their parents!) to function better during the day.

Melatonin and intestinal health. Several studies have shown that melatonin supplementation helps to prevent the erosion of the intestinal walls that can happen with the use of nonsteroidal anti-inflammatory drugs (NSAIDs).

Melatonin and jet lag. Although studies on melatonin and jet lag have produced varying results, I know plenty of frequent travelers who swear by it, including myself. Simply take one milligram a half-hour before you go to bed in your new time zone.

How To Use Melatonin
Because long-term research on melatonin has yet to be done, I don’t recommend that you take it every single day. I also don’t recommend frequent melatonin use in anyone under the age of 40. We still don’t know if frequent use will decrease your pineal gland’s ability to make the hormone, or if you will develop resistance to it that requires increasing doses over time. It’s been all but conclusively proven that melatonin is a safe and highly effective natural sleeping pill, far superior to addictive benzodiazepine drugs (which, by the way, suppress your body’s production of melatonin and decrease restorative REM sleep).

If you would like to try melatonin, start with the lowest possible dose—it’s available in 0.3 mg tablets. Use a sublingual tablet that dissolves beneath the tongue, and take it a half-hour before turning in. If you find that your usual dose stops working after a while, it’s better to stop taking it for a week or so and start again, rather than continually increasing the dose.

Note from Dr. John Lee
I wanted to add a few points to the article above on melatonin, regarding its relationship to breast cancer. This information is also found in What Your Doctor May Not Tell You About Breast Cancer.

In the early 1980s an American researcher discovered that melatonin prevents rats from developing breast tumors induced by the chemical carcinogen DMBA (dimethylbenzanthracene). Further studies with human breast cancer cells in culture flasks (in vitro) showed similar results; growth of the breast cancer cells were suppressed by 75 percent with melatonin. These test tube and animal studies support human clinical studies demonstrating that nighttime melatonin levels in urine are much lower in women with breast cancer than in healthy women.

In October 2001 the Journal of the National Cancer Institute published two independent studies showing that women who work night shifts may increase their breast cancer risk by up to 60 percent due to low melatonin levels and increased estrogen levels.

Another interesting observation that neurosurgeons have been making for many years is that the pineal gland in breast cancer patients is more likely to be calcified, which means it is likely to produce less melatonin.

High melatonin levels reduce the ovarian production of estrogens and progesterone and it is this feedback that is thought to be protective against breast cancer. Such studies, although not directly designed to investigate the role of melatonin on breast cancer prevention, may eventually shed light on this important topic.

This article was published in the John R. Lee, M.D. Medical Letter. Although the Medical Letter is no longer published, you'll find many articles from it on this website.


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