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The Illuminating Tale of Sunlight's Impact on Health

Sunlight may be today's most overlooked (and cheapest!) wellness essential.

Source: Kentoh/Fotolia

Could your kids be mal-illuminated?

Today's post is by Ken Cedar of Science of Light, a non-profit focused on photobiology--the study of light on living cells. Science of Light's mission is to improve children's scholastic performance by applying scientific principles of light to enhance cognition, well-being, and self-regulation. Grasping this information is crucial to appreciating how our electronically saturated world makes us ill!

SUNLIGHT — nature’s full-spectrum light — is the most overlooked wellness essential. Without the sun, there would be no life on this planet. Research shows that our genes are programmed to respond to exposure to full spectrum light now believed to be critical for the healthy development, growth and maintenance of your child’s body and mind.

Just like a green plant, our bodies require the full-spectrum of light exposure to thrive similar to the process of photosynthesis; a process used by plants and other organisms to convert light energy into chemical energy. Light striking the skin manufactures essential vitamin D (actually a hormone rather than a vitamin). Vitamin D has a major impact on our bodies and increases activation in more than 2000 genes that allows the body to combat disease. Light entering the body though the eyes regulates circadian rhythms (internal time clock), which are calibrated by exposure to natural light and darkness. Vital circadian rhythms control appetite, energy, mood, sleep, libido and other body-mind functions.

Our bodies are adapted to very specific lighting conditions: bright, balanced, full-spectrum light during the day and low level light in the evening followed by darkness. This rhythm of light and dark is what drives our circadian clock. Disregarding the biological adaptation to sunlight is a recipe for poor health because so much of our biology is regulated and influenced by the full-spectrum of light. Unfortunately for millions of people, including our children, the advent of the computer age has created an indoor lifestyle of ‘contemporary cave dwellers’ that are unwittingly starving for light! Weight gain, poor sleep, depression, fatigue and student learning disabilities are some of the negative side effects associated with being out of sync with the natural rhythm and radiant energy of sunlight.

The natural hours of light and dark each day regulate hormones like insulin, serotonin and dopamine. Light curbs melatonin production at the pre-optic site connecting to the pineal gland. Research on rats showed that light, even less than that of a candle, in the dark phase (night), disrupts the production of the antioxidant melatonin (the sleep hormone) and increases tumor growth. On the other hand, long dark nights change the metabolism from sugar burning to fat burning.

Artificially long hours of light—every day, all year long—eliminate seasons, as far as the body can tell. Some people get depressed in the winter. They may go for months with little or no exposure to natural sunlight. This can be countered by getting adequate sunlight or balanced, ‘sunlight quality’ full-spectrum light when indoors during the day, especially early morning light and by reducing the amount of artificial light in one’s environment at night. When using night-lights, use a soft/dim red (red does not interfere with melatonin production at night). When children get adequate light during the day and a good night’s sleep, they are better able to think, learn, and heal from illness, and the same is true for their parents.

In short, the full blend of light wavelengths in sunlight enables our bodies to react in a balanced and beneficial way, which is one of the reasons why regular sun exposure is such a critical component of a healthy lifestyle. Absorbing daily sunlight or balanced, full-spectrum light when indoors is an all-year ideal for optimum wellness and disease prevention. Additionally, it’s also important to reduce indoor environmental lighting (half hour to an hour) prior to bedtime, especially blue light emitted from cell phones, computers and TV, which inhibits the production of melatonin.

Since the beginning of human history, people have lived and worked outdoors during the light of day, absorbing light energy from the sky. An average of 10 hours outdoors each day, 70 hours weekly, was common. Pioneering photo biologist Dr. John Ott coined the term mal-illumination; a condition that he likened to malnutrition. “Mal-illumination is to light as malnutrition is to food.” Today, most people, young and old alike, suffer greatly from mal-illumination. Is it any wonder we experience many of the symptoms of being out of rhythm? Weight gain, fatigue, depression, headaches, pain, hormonal imbalances, sleep disorders, PMS, lowered immune responses, vitamin deficiencies and lack of vitality are but a few of the many health problems associated with mal-illumination.

Dr Dunckley's note: Science of Light offers a free e-Book, MAL-ILLUMINATION: The Silent Epidemic that I highly recommend, particularly with regard to explaining how light impacts hormone function. The "asynchronization" article in the reference section below is also good in explaining how light at night blunts serotonin. Increasingly I am seeing a variety of treatment refractory conditions that do not improve unless and until the nervous system is resynchronized, so awareness regarding light's impact on health has become critical. You simply can't fool Mother Nature!

For more help on how screen-time and screen light impacts children's physiology and functioning at home and school, see Reset Your Child's Brain: A Four Week Plan to End Meltdowns, Raise Grades and Boost Social Skills by Reversing the Effects of Electronic Screen-Time.


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Hollwich, F., and B. Dieckhues. “[Effect of light on the eye on metabolism and hormones].” Klinische Monatsblätter Für Augenheilkunde 195, no. 5 (November 1989): 284–90. doi:10.1055/s-2008-1050040.

Kohyama, Jun. “Neurochemical and Neuropharmacological Aspects of Circadian Disruptions: An Introduction to Asynchronization.” Current Neuropharmacology 9, no. 2 (2011): 330.

Lewy, A. J., R. L. Sack, and C. M. Singer. “Melatonin, Light and Chronobiological Disorders.” Ciba Foundation Symposium 117 (1985): 231–52.

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Smolders, Karin C.H.J., and Yvonne A.W. de Kort. “Bright Light and Mental Fatigue: Effects on Alertness, Vitality, Performance and Physiological Arousal.” Light, Lighting, and Human Behaviour 39 (September 2014): 77–91. doi:10.1016/j.jenvp.2013.12.010.