Sunlight: Good For the Eyes as well as the Brain

By April 29, 2015Exercise

Seeing the natural light of the sun helps the brain work better. No, not staring into the sun, but allowing the eyes to be exposed to natural outdoor light—contact lenses, eyeglasses, sunglasses and windows block the helpful sun rays.

Of course, the sun is important because it offers us vitamin D for free, and is the major source of this important nutrient that has powerful effects throughout the body. Vitamin D allows one to more effectively use calcium, improves the immune system, helps prevents cancer, and is important for brain function. Yet, millions of people have insufficient levels of vitamin D, and rickets—a once common condition of brittle bones in children caused by vitamin D deficiency that was very rare—has made a big comeback. Much of the information about vitamin D can be found in my books and articles.

In addition to the healthy affect on your skin, sunlight also provides another positive benefit. The human eye contains photosensitive cells in its retina, with connections directly to the pituitary gland in the brain. Stimulation of these important cells comes from sunlight, in particular, the blue unseen spectrum. A study by Dr.’s Turner and Mainster of the University of Kansas School of Medicine, published in the British Journal of Opthamology in 2008 states that, “these photoreceptors play a vital role in human physiology and health.” The effects are not only in the brain, but the whole body.

Photosensitive cells in the eye also directly affect the brain’s hypothalamus region, which controls our biological clock. This influences our circadian rhythm, not just important for jet lag but for normal sleep patterns, hormone regulation, increased reaction time, and behavior. Most cells in the body have an important cyclic pattern when working optimally, so potentially, just about any area of the body can falter without adequate sun stimulation. Turner and Mainster state that, “ensuing circadian disturbances can have significant physiological and psychological consequences.” This also includes “increasing risk of disease” as the authors state, and as numerous other studies show, including cancer, diabetes, and heart disease.

The hypothalamus also regulates the combined actions of the nervous and hormonal systems.

The brain’s pineal gland benefits directly from the sun stimulation. The pineal produces melatonin, an important hormone made during dark hours that protects our skin. In addition, melatonin is a powerful antioxidant for body-wide use, is important for proper sleep and intestinal function, and can help prevent depression. (Aspirin, however, reduces melatonin production.)

Among the specific affects of the eye’s photosensitive cells are helping you get out of bed each morning. The transition from sleep to waking up requires the effects of the body’s adrenal glands, influenced by the brain’s hypothalamus and pituitary. Exposure to morning sunlight also helps raise body temperature to normal (after a slight reduction during sleep), and numerous brain activities including increased alertness and better cognition—helping mood and vitality. These changes are often not experienced in many people until their morning coffee kicks in. Taking a peek outside at the dawn’s first sunlight is a habit worth implementing.

Aging reduces the ability to benefit from sun stimulation through the eyes, mostly due to eye-related disease development, especially problems such as glaucoma, and cataracts. Chronic inflammation and carbohydrate intolerance are two common problems associated with these and other eye illnesses.

Up to 70 percent of those 65 years and older have chronic sleep disturbances, with potentially any of the other health problems mentioned above. Turner and Mainster conclude that, “Light deficiency, whether due to improper timing, suboptimal spectrum or insufficient intensity, may contribute to medical conditions commonly assumed to be age-related inevitabilities.”

Inside lighting may provide some eye stimulation if your light bulbs are the full spectrum type. But it won’t take the place of a regular habit of getting morning sun into unshielded eyes. This routine is even more important with age.

The bottom line: The sun can help brain function, which can improve the nervous system, hormonal regulation, muscle function, immune health, and carries many other benefits.

Join the discussion 5 Comments

  • Thomas Sanocki, PhD says:

    This means we (who wear glasses) should be outside with our glasses off. An easy experiment to try! It also means people without glasses should be healthier? A fairly easy experiment to do.

    • Thomas:

      People who wear glasses can be healthier or unhealthier than people who don’t for a formidable array of reasons. My guess is that if you do a univariate epidemiological study on the health of glasses-wearers as compared to non-glasses-wearers, I’d be surprised if you find any effect at all. What I would expect, however, is that if you produce the effects of not wearing glasses for a glass wearer (within-subjects comparison), you might see a difference if the effect is strong enough.

      However, I would expect the effect of not wearing glasses vs. wearing glasses to be much smaller than the effect of not getting enough sunlight (amount X) vs. getting enough sunlight (amount Y), on the same dependent variable. So, glasses-wearers may be healthier than non-glasses-wearers in a strictly subclinical sense, where you’d expect clear clinical implications only when wearing glasses (or not) stacks together with an array of correlated or uncorrelated variables. But even supposing that wearing glasses only has subclinical effects over not wearing them (i.e. it doesn’t make you measurably unhealthier), that wouldn’t mean that wearing glasses isn’t pressing down slightly on the “unhealthy” end of the scale.

  • glasseson says:

    The effect of getting run over by a car because of not wearing glasses would have severe consequences for your health.

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