It’s been called the “hormone of darkness” because your body makes it almost exclusively at night. The pineal gland secretes melatonin during the night to regulate sleep, and supplemental melatonin is a popular remedy for insomnia and jet lag. I’ve used it with good results. For jet lag, I’ll take 2.5 mg of a sublingual (under the tongue) tablet at bedtime for a night or two upon arrival. I’ll take the same amount for occasional insomnia, although a much lower dose, about 0.3 mg, appears to be more effective if you’re taking melatonin for more than a few consecutive nights. I like the increase in remembered dreams that I get from melatonin. (A few unlucky individuals report nightmares.)
Researchers are reporting that supplemental melatonin may have many other benefits, including prolonging the lives of various cancer patients. Plus, there’s increasing evidence that the melatonin made by your body doesn’t just regulate sleep but also helps protect against breast cancer.
Nighttime light, melatonin, and breast cancer.
Scientists have long known that breast cancer rates are much higher in industrialized nations than in developing countries. In 1987, cancer epidemiologist Richard Stevens, PhD, proposed that artificial light at night might increase breast cancer risk by suppressing melatonin production. Several years later, Stevens and other researchers showed that women who work frequent night shifts—and are exposed to a large amount of light at night—are more likely to develop breast cancer (Journal of the National Cancer Institute)
More recently, researchers found that women who have higher levels of melatonin are at lower risk of getting breast cancer (Journal of the National Cancer Institute, July 20, 2005). Another study compared the effects of pumping melatonin-rich or melatonin-depleted blood into human breast tumors implanted in rats. The melatonin-depleted blood, drawn from women after 90 minutes of exposure to bright nighttime light, spurred tumor growth in the animals. In contrast, the melatonin-rich blood, collected after two hours of darkness, slowed tumor growth. Further experiments by the same researchers suggested that melatonin can “put cancer cells to sleep” by blocking their ability to soak up linoleic acid, an omega-6 fatty acid that’s in polyunsaturated vegetable oils and that can promote cell proliferation (Cancer Research, December 1, 2005).
So far, there have been no studies on whether melatonin supplements can reduce breast cancer risk in humans. But it may be wise to take steps to increase your body’s natural production of melatonin. Don’t skimp on sleep, and avoid bright light once you’ve gone to bed. That means not falling asleep with the bedroom TV on and using a nightlight rather than the bathroom light for nightly trips there. (Dim light has relatively little effect on melatonin.) Get regular exercise, which boosts melatonin production and also encourages sounder sleep. Consider taking up meditation: Several studies show that meditating regularly can increase blood levels of melatonin. And avoid evening use of melatonin-suppressing substances like alcohol and beta-blocker drugs.
Promising uses of melatonin.
I’ve been pleased to see research suggesting that melatonin supplements may extend survival in certain cancer patients. A recent meta-analysis of 10 European trials examined the effects of large doses of melatonin (10 to 40 mg a day) in people with solid tumor cancers, including lung, brain, skin, renal, and breast cancer. Taking the hormone reduced the risk of death at one year by 34 percent, and no serious side effects were reported (Journal of Pineal Research, November 2005).
Donald Abrams, MD, chief of hematology/oncology at San Francisco General Hospital and a graduate Associate Fellow of the Program in Integrative Medicine, says melatonin has been best researched in non-small cell lung cancer patients, and a US study involving such patients is under way. He suggests that people with this malignancy take 12 to 20 mg of melatonin a day at bedtime, and I think anyone with a metastatic solid tumor may benefit from the same dosage.
Melatonin looks promising for other health problems, although much remains to be learned about how it helps:
- Headaches. A Brazilian study of migraine patients found that taking 3 mg of melatonin 30 minutes before bedtime for three months cut headache frequency by at least 50 percent in most participants, and both migraine intensity and duration also decreased (Neurology, August 24, 2004). Earlier research in Italy suggested that using melatonin at a dose of 10 mg each evening could help prevent cluster headaches (an excruciating type that occurs about the same time each day for weeks or months) once a cluster period has begun.
- High blood pressure. In a study of men with untreated hypertension, those who took 2.5 mg of melatonin one hour before bedtime for three weeks had a significant decrease in nighttime blood pressure levels—a six-point average drop in systolic blood pressure and a four-point drop in diastolic pressure (Hypertension, February 2004). The same researchers are now exploring whether melatonin supplements can improve sleep in women and men with hypertension who are on beta-blockers, which lower melatonin levels.
- IBS. A study in Singapore involving people with irritable bowel syndrome (IBS) who had sleep disturbances found that taking 3 mg of melatonin at bedtime for two weeks reduced abdominal pain, even though there was no improvement in sleeping problems