Let There Be Dark

Posted on December 9th, 2008 by author  |  2 Comments »

When I’m not devouring the pages of a sports magazine, one of my other favorite light reading materials would be National Geographic. There’s never a lack of interesting stories about anything and everything related to our planet.

However, the story that caught my attention in last month’s issue wasn’t about the usual stuff of people, animals or the environment. The article was entitled Our Vanishing Night and it discusses the problem of light pollution.

The first time I’ve heard of light pollution, I just shook my head because I was surprised to learn that light can also be a pollutant. Light pollution is the excess light generated by human activities that shines outward and upward into the night sky and is enough to obscure many stars and other heavenly bodies.

When man-made light spills into the natural world, some aspect of life like migration, reproduction and  feeding will be affected. Because light is very powerful biological force, it draws many animals to it like a magnet. For example, migratory birds can collide with tall buildings with bright lights. Songbirds sing during unnatural hours in the presence of artificial lighting. Sea turtles, which lay their eggs on dark beaches, have difficulty finding their nesting spots.

Many nocturnal mammals also look for food more cautiously due to light pollution because they’ve become easier targets for predators.

Light Pollution and your Health

We humans also need darkness. I learned through the article that darkness is important for our biological welfare because the regular oscillation of waking and sleep is a biological expression of the regular oscillation of light on Earth.

A group of cells in your brain located in the hypothalamus called the Suprachiasmatic Nucleus (SCN) controls your biological clock because the cells that form the SCN react to light and dark signals. Light travels through your eyes’ optic nerves to your SCN where it tells your body that it’s time to wake up. Light also signals your SCN to start other activities associated with being awake, like increasing your body temperature and producing hormones like cortisol.

When your eyes signal to your SCN that it’s dark outside, your body will begin to secrete melatonin, the hormone that induces sleep. How much melatonin you produce is related to the amount of bright sun exposure you have had the previous day. The less bright light, the lower the production of melatonin.

Aside from inducing sleep, there are many studies that show that melatonin also decreases your risk of cancer. So if your sleep is disrupted by light pollution, your melatonin levels will go down, increasing your risk of cancer.

At least one new study has suggested a correlation between higher rates of breast cancer in women and the brightness of their neighborhoods at nighttime. One of the first studies linking cancer to light showed that blind women have a 36 percent lower risk of developing breast cancer compared to women with sight. Because blind women do not respond to light, they maintain high melatonin levels at night regardless of how much light is available to them.

Fortunately, among the earth’s pollution problems, light pollution is perhaps the easiest to remedy because it is not persistent. Simple changes in lighting design and installation will greatly reduce the amount of light spilled into the atmosphere and also save energy.

I was surprised to read in the article that one of the first efforts made to control light pollution was started 50 years ago in Flagstaff, Arizona, which is home to the Lowell Observatory, a National Historic Landmark and one of the oldest observatories in the country. In fact, Flagstaff was declared as the first International Dark Sky City in 2001.

When Dark is Good for You

When I was very young, I used to sleep with the lights on because I was afraid that a monster might pop out from under my bed or barge through the door and windows. I was only able to sleep with the lights off when accompanied by someone (preferably an adult) in my room. Of course, I’ve outgrown that silly habit by time I was a teenager and I have been sleeping soundly in the dark ever since.

Sleeping in a pitch-black bedroom may be one of the best and easiest things you could do for your health. Even the dimmest glow of light from a source like your clock radio could be interfering with your sleep, and ultimately, your long term health and risk of developing cancer.

Get your room as dark as possible by:
• Installing blackout drapes
• Closing your bedroom door and covering the base to prevent light from seeping in
• Getting rid of your electric clock radio or at least covering it during bedtime
• Avoiding all kinds of night lights
• Keeping all the lights off at night (including when you get up for a bathroom break)

You’re bound to notice a major improvement in your sleep once you eliminate the sources of light pollution in your room. Sweet dreams!

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Responses to “Let There Be Dark”

  1. Alison says on :

    Hi Dr. Mercola…just stumbled upon your blog. Thank you for providing such thorough information on this very important topic. I’ll visit again soon…. ~ Alison

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