Part Three – The Importance of Bright Light

Many of the important systems in our body like sleep, body temperature, cortisol (stress hormone) and growth hormone go through a 24 hour cycle or Circadian Rhythm. How alert and effective we are is largely determined by where we are in our cycle. Where we are in the cycle is determined by when we are exposed to bright light (usually meaning outside during the day).

Light intensity is measured in lux and during the day the typical intensity is around 10,000 lux. Indoors in our offices the intensity is only about 500 lux or 1/20th that of the outdoors. Our homes are frequently even less. Light intensity is reduced by going through glass like in your car and by sunglasses. You don’t have to be in direct sunlight to get an adequate intensity level – it can be reflected light.

Bright light means, time to be productive, crank up the energy, and get motivated. Decreasing light means time to start shutting it down. Bright light raises serotonin. Low light decreases serotonin. Low serotonin increases carbohydrate craving. Studies are finding that during the shorter, less bright winter months our serotonin levels are lower (in all of us) and we are inclined to eat more carbs. People who are susceptible to certain kinds of depression will actually feel depressed when their serotonin levels are low. Eating carbs raises serotonin.

For many of us it’s not practical to be outside much, especially in the morning. If you go outside at noon and spend an hour or so you may be setting the sleep clock in your brain for 16 hours later, which would be 4 am.  This is probably one of the causes of insomnia for many people. However, there are lamps you can buy that provide adequate light intensity and though they are somewhat costly at about $150, they have come down some since originating. There is some debate as to whether you need full spectrum light including ultraviolet (tanning rays) and infrared (heat rays) or just intense bright (white) light. White light is probably all we need. These lights can be put by the bed to read the morning paper, or on our desks, and the one I have is about the size of a loaf of bread.

These lights may improve energy, mood, and sleep, and bright light can even decrease bingeing in some bulimics. They may replace or lower the dose of antidepressants for some people, and many antidepressants make it hard to lose weight since they can make the brain act as though they have genetic obesity.  Increasing bright light can help with weight control by increasing energy and metabolism and by reducing the need for meds that cause weight gain.

 See Part Four – Genetic Obesity

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