Melatonin: the Sleep Hormone that Prevents Cancer

Melatonin is a hormone secreted by the pineal gland. When it gets dark at night, melatonin levels rise, making you sleepy, then fall in the morning when you are exposed to light. During the 1990s, mental health investigators found a link between seasonal depression and light exposure. People living in high latitudes which exposed them to less light during the winter had a higher incidence of depression, compared with those living closer to the Equator. It was hypothesized that persistent high melatonin levels from the night led to depression. As a treatment, patients were given light visors in the morning. It did not work so well, until it was discovered that actually only the shorter wavelengths of light -the blue and the blue-green (aqua)- were effective in signaling the pineal gland to turn off melatonin secretion.

The aviation medicine community picked up on this, rather quickly, and began studying different colors of light, in terms of effectiveness in telling the pineal gland to turn off in the morning. Meanwhile, epidemiological studies revealed a striking association between sleep and cancer. Women suffering from cortical blindness (unable to see anything) were shown to have half the breast cancer rate as sighted women. At the same time, women such as nurses, factory workers, and flight attendants, who worked "graveyard shifts", had double the risk of developing breast cancer, compared to women who did their sleeping at night. In epidemiology, such strong associations between a behavior and a disease are very rare. Only smoking, or having several first-degree relatives with breast cancer, put women at higher risk for breast cancer compared with exposure to light at night.

During the last decade, new studies have found associations between exposure to light during the night hours and cancers other than breast cancer, for women, men, and children. The working hypothesis, which I suspect will be proven correct within a few years, is that the advent of electric lighting at night is one of the major reasons why the cancer rate has increased substantially during the last 100 years. The reason for this is melatonin. This hormone, which puts us to sleep, is a powerful anti-oxidant and cancer preventive agent. Results of in vitro and in vivo studies, suggest that melatonin helps the immune system to eliminate neoplastic cells, before cancer takes root.

What can you do about this? First of all, sleeping in complete darkness is very important. If your bedroom is not dark, wearing a sleeping mask keeps your melatonin levels high throughout the night. Interrupting the darkness, however, for example by turning on a bathroom light, even for a few minutes, can turn off your melatonin for an hour or more! That’s why for many people it’s difficult to go back to sleep after getting up to go to the bathroom.

The good news is that the very same studies which taught investigators how to use blue and aqua light in the morning to turn off melatonin led to other studies teaching us which kind of light prevents melatonin from being turned on at night in the first place (or for that matter turning it off in the middle of the night, if you get up and turn on a light). It is not the entire visible light spectrum, but just the blue to aqua range, as illustrated in this picture. This means that  you don’t need to walk around in the dark in the name of health. You simply need to filter out the blue to green part of the light spectrum. Do this, you can go about your normal activities, even into the late hours of the night, without inhibiting your pineal gland from secreting the melatonin that helps you to sleep soundly, while helping to prevent cancer as well!

*source: http://factoidz.com/