Human body have been exposed to roughly equal amounts of sunlight and darkness, throughout its evolution. So our bodies have evolved to synchronize with this switching of night and day. When Thomas Alva Edison invented the light bulb, it changed everything. We started enjoying more light. But our bodies couldn't catch up with this sudden change brightness.
Our bodies produce the hormone melatonin in response to darkness. The photosensitive cells of the retina of our eyes send signals to the brain which then produces melatonin, releasing it into the blood stream. It is an important hormone in controlling our circadian rhythm or the biological clock. Melatonin is also a potent antioxidant.
A research done using mice revealed that when exposed to light during the night, increased the chances of developing cancer. And the researches believe that the results can be applied to humans.
Studies have shown that blind women have 50 percent less breast cancer incidence compared to women with intact eye sight. It is interesting to note that blind people (as far as their photosensitive cells were concerned) were exposed to twice the amount of darkness than usual.
This benefit in reduced cancer risk may well be due to the antioxidant properties of melatonin. Antioxidants prevent the oxidation of DNA leading to mutation. The mutations can trigger uncontrolled proliferation and cancer of those cells.
So the next time you fall asleep, remind yourselves that switching off those lights can help you fight cancer better.