Can exposure to light make you feel good, boost your resistance to disease, and make you more alert during the day and better able to sleep soundly at night? Without a doubt. And like that image we see in cartoons, the light bulb is beginning to go on above heads everywhere as the truth becomes more and more apparent: Light plays a crucial role in helping the body function normally and produce the right amount of the essential hormone melatonin.
Certainly, nutrition, exercise, and lifestyle are extremely important ingredients needed for maintaining (or rebuilding) health, but what if I told you that, by making some simple changes in regard to your exposure to light, you could feel better, sleep better, and reduce the risk of some serious diseases? Would you do it?
Step into the light
Though the majority of people remain very much in the dark on this subject, scientists now know a great deal about the major effect light has on health. Truly, light rules the body, and different wavelengths of light affect us at different times of the day.
SAD, which stands for seasonal affective disorder, is a widely known acronym, probably because it fits the condition so well. Many people suffer from depression in the winter months due to a lack of sunlight. But the way light affects us -- physically, mentally, and emotionally -- is far more complicated than simply cheering us up and dispelling gloom.
Similar to the way processed food has interfered with the body's assimilation of essential nutrients, the introduction of artificial light into our daily environment has led to serious disruptions of the "light cycle," which refers to the biological need for alternating periods of light and darkness.
Human beings evolved around this principal. We are hard-wired to react to different types of light, which can affect our level of alertness or drowsiness by acting either to reinforce or to disrupt what biologists refer to as our "circadian rhythms."
Derived from the Latin term circa diem, meaning "about a day," circadian rhythms serve to regulate our daily sequence of metabolic and behavioral changes. As described in a study from Chicago's Rush University Medical Center, these intrinsic cadences "are coordinated by an internal biological clock" situated in a part of our brain's hypothalamus region
The unnatural manner in which we light up our lives and the resulting alterations in sleep patterns have taken a heavy toll. It's somewhat ironic that Thomas Edison, the man who refined the invention of the incandescent bulb into a commercially viable commodity, was a person who didn't believe in sleep, often quoted as saying that sleep is a "waste of time."
But Edison aside, as I've discussed in a number of blogs on my website, getting a good night's sleep is essential to overall health, and the lack of sleep, from which an estimated 70 percent of Americans suffer, can contribute significantly to our susceptibility to all manner of illness, including weight gain.
More recently, studies have increasingly pointed to the effect of exposure to different types of light on melatonin production, which is a key factor in determining not only how soundly we are able to sleep, but how "awake" we are at peak times of the day and in the long run, whether our health improves or deteriorates.
Melatonin, which is produced by the pineal gland, located near the center of the brain, is a highly light-sensitive hormone, which is to say that it can be "turned on or off" to a large degree by the presence or absence of light. In general terms, darkness or dim light stimulates melatonin production and its resultant drowsiness, which enables us to sleep, whereas bright light -- whether it is sunlight or artificial light -- stems the flow of this sleep-inducing substance, making us more alert. While our natural circadian rhythms are set to trigger our melatonin mechanism at certain preset times, you might say that light can be used to override it.
When it comes to influencing melatonin production and our resultant alertness or sleepiness, what researchers have been finding is that not all light is created equal. Like a rainbow, light comes in different colors, which are transmitted via the retina of the eye to a mechanism called the suprachiasmatic nucleus in the hypothalamus area of the brain that's responsible for regulating our circadian rhythm.
And though it might seem counter-intuitive, the color that keeps us awake is blue, while the ones more conducive to sleep are at the red end of the spectrum. And these days, the light to which we're exposed at the time our biological clocks should be getting ready to crank out melatonin tends to be bluer than ever, due primarily to the many computer-related activities that we tend to engage in just before bedtime, whether they involve work, fun and games, or communication and social media, as well as the phasing out of old-fashioned incandescent bulbs that had more of a reddish glow to them.
Blue wavelengths -- which are beneficial during daylight hours because they boost attention, reaction times, and mood -- seem to be the most disruptive at night. And the proliferation of electronics with screens, as well as energy-efficient lighting, is increasing our exposure to blue wavelengths, especially after sundown.
If this simply robbed us of sleep, it would be bad enough. But considerable evidence is emerging that melatonin is essential to good health and that suppressing it in this manner can lead to the onset of some serious diseases.
For example, a study involving 740 women conducted by researchers from the Harvard School of Public Health and the Department of Medicine of Brigham and Women's Hospital in Boston, and published in the April 2013 edition of the Journal of the American Medical Association, found that the lower the melatonin levels, the higher the risk of developing Type 2 diabetes.
"This is the first time that an independent association has been established between nocturnal melatonin secretion and Type 2 diabetes risk," noted the study's chief author, researcher Claran McMullan.
One reason for this lowered risk may be that melatonin production helps fight obesity, as was indicated by another recent study published in the Journal of Pineal Research and performed on laboratory rats by scientists from the University of Granada Institute for Neuroscience, the Hospital Carlos III, Madrid, and the University of Texas Health Science Center in San Antonio. The study found that melatonin stimulates a type of fat cell called beige fat that burns calories in living organisms instead of storing them, helping to regulate body weight and metabolism.
Melatonin is also a powerful antioxidant, which may help account for findings that shift workers tend to have higher rates of cancer -- so much so, in fact, that in 2007, the World Health Organization declared shift work to be a probable carcinogen. In a 2009 examination of sleep disturbances and cancer risk, Dr. David E. Blask of Tulane University maintained that such individuals who are exposed to light on a regular basis at night "are not only immune suppressed but they are also at an increased risk of developing a number of different types of cancer." He further noted that "mutual reinforcement of interacting circadian rhythms of melatonin production, the sleep/wake cycle and immune function, may indicate a new role for undisturbed, high-quality sleep, and perhaps even more importantly, uninterrupted darkness, as a previously unappreciated endogenous mechanism of cancer prevention."
Some tips to get your 'light right'
As the American Medical Association said in a 2012 policy statement, "the power to artificially override the natural cycle of light and dark is a recent event and represents a man-made self-experiment on the effects of exposure to increasing bright light during the night..."
While we certainly will never return to the time when sunset was the end of our work day and we pretty much had nothing else to do but to go to bed, there are ways to adjust our exposure to light that can help set our instinctive biological "clock" back to a more normal rhythm and allow our bodies to function more on the "time zone" nature intended:
- Don't go to sleep "blue." Stop going to bed with your tablet, smart phone, or e-reader. Not only do they all emit blue light, but the manner they are used -- right up close to your face -- makes the effects of this "alert" light even more powerful.
- "Words with Friends" can wait. Get off your computer -- another device that emits blue light-- two to three hours before bedtime. It has an “off” switch for a reason.
- Keep the television out of your bedroom. Not only does it emit blue light but watching scary or intense shows (especially the nightly news report) won't do anything to add to a decent night's sleep.
- Sleep in the dark. That may sound like simplistic advice, but look around your bedroom. Do you have a clock radio, CD player, or iPhone dock by your bed? Do they give off any light? If so, cover them up, or better yet, remove them.
- Get at least 20 minutes exposure to daylight regularly. This will help you sleep better at night, enhance melatonin production, and put you in a better mood and more alert state during the day.
To your good health,
Mark Hyman, MD
Mark Hyman, MD is a practicing physician, founder of The UltraWellness Center, a six-time New York Times bestselling author, and an international leader in the field of Functional Medicine. You can follow him on Twitter, connect with him on LinkedIn, watch his videos on YouTube, become a fan on Facebook, and subscribe to his newsletter.
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1. Smith, Fogg and Eastman, "A Compromise Circadian Phase Position for Permanent Night Work Improves Mood, Fatigue, and Performance ," Sleep, Vol. 32, No. 11, 2009.
2. "Blue light has a dark side," Harvard Health Letter, May 2012.
3. "Diabetes Risk Linked to Melatonin Secretion During Sleep," Medical News Today, April 19, 2013.
4. Melatonin Helps Control Weight Gain as It Stimulates the Appearance of ‘beige Fat’ That Can Burn Calories Instead of Storing Them, Study Suggests," Science Daily, Sept. 25, 2013.
5. Blask, David E.," Melatonin, sleep disturbance and cancer risk," Elsevier, Sleep Medicine Reviews 13, 2009.