But melatonin does much more, especially in higher quantities. It’s being used to protect against cancer, and to enhance the effectiveness of cancer treatments.

This hormone regulates the patterns of wakefulness and sleepiness that coincide with light and darkness known as circadian rhythm. Melatonin levels should be highest at night and lowest during the day. But light shuts down your body’s production, so if you're in a well-lighted room late at night you may not be able to make enough melatonin to sleep well.

The melatonin/cancer connection
Exposure to light at night not only affects your ability to sleep during the day, it also increases your risk for cancer. Studies show that women who work late night shifts have an increased risk for getting breast cancer. And if you work late at night for just three nights a month over a period of 15 years, your risk for colon cancer escalates.

For a long time, we couldn't explain this phenomenon. Recently, however, a group of circadian-clock control genes were discovered that regulate the growth of normal cells and cancer cells. When these genes mutate, they cause a spontaneous outbreak of cancer. Why do they cause specific cancers? We don’t know yet.

Circadian rhythm organization
Cancer cells multiply at certain times of the day, so it stands to reason that cancer therapies should be timed with cancer cell growth. Yet, cancer treatments are given at times that are most convenient for doctors and patients — not at times when a hormone, nutrient, or medication would work the best. This just doesn’t make sense.

We have some studies that support giving cancer treatments according to circadian rhythms. One study showed that there was less toxicity and a better response from drug therapy in patients with colon cancer who were given their medication at night. Combine traditional treatments with melatonin, and the benefits increase dramatically. Let's take a look at some good studies on this subject.

A group of patients with advanced cancer were given 10 mg of melatonin at night for at least two months along with their other medications. They lost less weight and their disease progressed more slowly than those on the same therapy who didn’t take melatonin.

Melatonin added to prescribed medications was also associated with survival for more than a year in people with brain cancer, melanoma, lung cancer, and untreatable glioblastoma. The combination worked better than the medications alone.

But that's not all
Melatonin is an aromatase inhibitor. Aromatase means that it reduces the ability of male hormones (adrogens), such as testosterone, to turn into estrogens. This means that melatonin has anti-estrogenic effects. When you combine it with tamoxifen, it actually enhances tamoxifen’s effects. Melatonin also boosts the effectiveness of interferon on kidney cancers.

I'm particularly impressed with how this hormone protects healthy cells from toxins, such as chemotherapy, radiation, and other drugs. Perhaps this activity explains why it has proven to be so useful in people with untreatable cancers.

In several studies, there was less muscle wasting, less weakness, and a longer survival when patients were given 20 mg of melatonin at night along with either chemotherapy or supportive care.

What does this mean for you?
I'm not suggesting that you start taking high doses of melatonin even though there a number of supplement companies that sell it in 20 mg tablets. Melatonin is a hormone, and while I think that up to 3 mg a day is safe to take, I think that higher amounts should be monitored by your doctor, especially since there are interactions between melatonin and some pharmaceutical drugs. You don’t want the melatonin to increase the activity of other drugs without your doctor’s knowledge.

You might, however, show him or her this article and suggest they read some of the studies I've cited. Melatonin could be an appropriate nutrient to take for women who have hormone-related breast cancers, for people with inoperable cancers, and to protect you if you’re at a particularly high risk. This is a subject that's worth exploring.

Cos, S., et al. e-pub ahead of print, Int J Cancer, 2005 August 3.

Lissoni, P., "Is there a role for melatonin in supportive care?" Support Care Cancer, 2002 March; 10(2).

Mahmoud, F., et al. "The therapeutic application of melatonin in supportive care and palliative medicine," Am J Hosp Palliat Care, 2005 July-August; 22(4).