In my last post I discussed some of the evolutionary aspects of darkness and addressed humans’ psychological issues around it. Here I would like to shed some light on one tiny example of how altering our environment has a direct effect on our own health and longevity.
A large body of research demonstrates that the master hormone, melatonin, has a powerful influence on the development and growth of cancer cells. Melatonin, which is one of the few hormones that is present in all animals and some plants, is produced by the pineal gland in response to darkness. It plays an indispensible role in the regulation and coordination of circadian rhythms, hormone levels, reproductive cycles, feeding times and neurotransmitter levels in all animals. We’ve known for a long time that melatonin suppresses tumor growth by altering the cell’s use of fatty acids. The evidence also suggests that it alters estrogen sensitivity of cells helping to slow or arrest the growth of breast, prostate and uterine cancers. Small disruptions in the amount of light an organism is exposed to can result in significant drops in the production of melatonin. A study conducted by R.T. Dauchy et al. demonstrated that very small amounts of light (.2 Lux which is that of a full moon under clear conditions or that of a door cracked into a lighted hallway) suppressed melatonin production in cancerous rats by 87% with a corresponding increase in tumor growth. Rats that were exposed to 24 hours of light had only a slightly higher reduction in melatonin levels. Another well-done study demonstrated that melatonin levels were affected by light spectrum more than intensity (lux). Light emitted at shorter wavelengths, similar fluorescents and LEDs, resulted in almost a two-fold reduction in melatonin levels. Light emitted at shorter wavelengths similar compact fluorescent or sodium bulbs had a lesser effect.
There are literally thousands of studies showing the strong link between cancer rates and melatonin levels. A large study even showed a statistically significant reduction of hormone-sensitive cancers in blind men and women.
Everyday our bodies develop hundreds, if not thousands, of cancer cells. Along with our immune systems we have several lines of defense, like melatonin, that serve to slow growth and destroy these cells before they develop into tumors. Out of the illusion of safety, light pollution has become a pervasive force in the developed world and darkness is becoming a precious commodity. As we in the Northern Hemisphere approach the winter solstice, might I suggest that we take steps to bring the safe and lovely darkness back into our lives.
- Turn off unneccesary exterior lighting – is any of it really necessary?
- Keep indoor lighting to a minimum as darkness falls.
- Consider implementing one night per week with minimal light exposure and go to bed early.
- Draw your bedroom shades.
For more information on other things you can do including lighting that has a lesser effect on you and the ecosystem that you are a part of, please visit The International Dark Sky Association.by