See the light

By Miranda

We really underestimate the impact that light has on our bodies. This time of year in the Northern hemisphere brings less exposure to daylight. It is cold/rainy/windy, so we avoid spending time outdoors in the daytime. Most people spend their waking day indoors in their workplace. And due to the shorter days, it is less likely that any of us really encounter much daylight outside before or after work.

But we get plenty of light inside from light bulbs, though. Or from computer screens, phones, e-books, and other electronic devices. This light is less bright than natural sunlight, but much brighter than moonlight. So, let's call this artificial light "medium light."

The body reacts to light all of the time.

Our body produces melatonin and cortisol to create our "circadian rhythm", our cycle of being asleep and being awake. High melatonin levels at night help induce sleep. High cortisol levels in the morning induce wakefulness.

If we lived outside as the animals we are, we would be exposed to much daylight during the day, and only moonlight at night. In our cozy buildings, however, we get this "medium" light consistently throughout the day. This means not enough daylight during the day and too much light in the evening.

During the day, when our cortisol levels are prone to be their highest, we should be exposed to a great amount of light. In particular, the blue spectrum of light (short wavelength), like those obnoxiously bright headlights you see on cars from time to time. If we are exposed to this spectrum of light from 7am to noon, we produce as much as 50% more of the "awake hormone" at this time than we would without this bright light exposure. (1)

Can you imagine being 50% more awake in the morning? Doesn't that sound great?

But exposure to light at night has a negative effect. Exposure to this blue spectrum light in the evening results in a dramatic drop in melatonin production, even in small amounts of light exposure. This means more difficulty getting to sleep, a hard time staying asleep, or lower quality of sleep. (1)

Interestingly, exposure to light in the red spectrum (long wavelength) does not suppress melatonin production like blue light does. According to the research, there is no statistical difference between red light and darkness when it comes to affecting our melatonin levels. (1)

For a wakeful, energetic morning:

• Exposure yourself to blue-spectrum light when you first wake up. Consider vanity lights in your bathroom that you only use during the day to help balance your circadian hormones. The type of light bulb you want for this is common, the "full-spectrum fluorescent." If the bulb has a recorded "color temperature", you want 5000 or higher. Standard CFL bulbs you can find at most any market are usually 5000, which is very effective. Harder to find and a little more costly are "sun lamps" used for treating seasonal affective disorder, which usually measure 5500 in color temperature. For reference, the light outside on a cloudy day is 6500. 

• If cloudy daylight is still 6500, and our best bulbs are only 5500, it is still most effective to get some exposure to real daylight in the morning. Consider challenging yourself with a walk outside first thing when you wake up (or as soon as it is light out). What a healthy habit for more than just your circadian rhythms! 

• Between 7am and noon, try to optimize your indoor light by sitting near a window or taking a walk outside on your lunch break. 

• Be sure to open your shades and blinds as the sun rises in the morning, if you are at home, in order to maximize your morning light.
  

For a deeper rest at night:

• As the evening wears on, try to turn off as many lights as possible to reduce your exposure to the wrong light at night. We begin producing sleep-inducing levels of melatonin around 8:00pm, and its production peaks at midnight. By 8:00, begin shutting off unnecessary lights and lamps so your body can prepare for bed internally. 

• Consider replacing a few key lights in the house (in places where you spend your time before bed) with red-spectrum bulbs that don't suppress the body's production of sleep hormone. A bulb with a color spectrum of 4000 or lower is best. Old incandescent yellow-tinged bulbs (that are mostly being replaced by the compact fluorescents) generally measure around 3000. A red incandescent light bulb will usually measure around 2700, and is a great choice for evening light if it is bright enough for you to see by. 

• If you use a night light, be sure that it is a red or amber colored light, and not the bright blue of a fluorescent bulb.
  

• Here's the hard one: television and electronic devices. Your best choice is to turn them off at 8pm and read a book by red light instead. Many people won't go for that. If you suffer at all from sleep disturbance or seasonal depression and are exposed to bright light in the evening, consider getting some blue-light-filtering glasses. Glasses like these will not only make you look pretty cool wearing your sunglasses at night, but are affordable and block out all of the melatonin-suppressing light. So you can still watch tv and play on your i-pad, hooray! Just be sure not to ever wear them during the day.
  

I have met very few people that don't have any difficulty with sleep AND also feel energetic in the morning. So please don't take light for granted. Some very simple changes in light exposure can make significant changes to your health, especially during the darker months.


1. Mariana G. Figueiro and Mark S. Rea. The Effects of Red and Blue Lights on Circadian Variations in Cortisol, Alpha Amylase, and Melatonin. 2 March 2010. http://www.hindawi.com/journals/ije/2010/829351/