July 18, 2008 Blogs by: Tim Jennings, M.D.

Many people recognize sunlight as one of God’s “natural remedies.” Sunlight kills many germs, stimulates photosynthesis in plants, affects circadian rhythms (our biological clock and such things as the sleep/wake cycle), and impacts mood.

Many people are aware that too much sun exposure increases the risk for skin cancer and because of this risk have begun avoiding sunlight. But should we be avoiding all sunlight? Or is there a healthy balance? Do we actually need sunlight exposure for optimal health? Science has recently discovered two surprising benefits to sunlight which document its beneficial effects.

There is evidence now emerging that sunlight in moderate amounts, enough to pink the skin but not enough to cause sun burn, actually reduces the rate of cancers. Sunlight stimulates the production of the active form of Vitamin D which has been demonstrated to reduce the rate of cell proliferation and thus inhibit cancer growth. Vitamin D has been shown in the lab to slow the growth of cancers of the colon, breast, prostate, lung, skin and leukemia. Epidemiological evidence supports this idea with evidence suggesting those with the greater sun exposure have the lowest rates of these cancers. Additionally, Vitamin D is essential for developing and maintaining strong bones and evidence is emerging that rickets (weak bones) is on the rise as more children are being kept out of regular sunlight. 1

As a psychiatrist I am particularly intrigued with a recent study evaluating the impact of sunlight on patients with dementia. It is a well known fact that patients with dementia have alterations of their sleep/wake cycle, suffer from confusion, agitation, mood problems, and organizational difficulties. To explore the potential impact sunlight may have on these symptoms researchers evaluated 189 residents of 12 Dutch assisted care facilities. The residents were randomized to experience daily bright sunlight (1000 lux) or dim light (300 lux) and patients were evaluated for changes in cognition, mood, and function. Amazingly, sunlight reduced cognitive decline by 5%, depression by 19%, and physical functional decline by 59%. The improvements were comparable to what is seen with medication. 2

God has provided many natural resources that when used in moderation provide health to our minds and bodies.  Ssunlight, it appears, is one of those genuine “natural remedies.”

1. New Scientist, 09 August 2003, 2407.

2. JAMA 2008 Jun 11; 299:2642.

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Tim Jennings, M.D. Timothy R. Jennings, M.D., is a board-certified psychiatrist, master psychopharmacologist, Distinguished Life Fellow of the American Psychiatric Association, Fellow of the Southern Psychiatric Association, and an international speaker. He served as president of the Southern and Tennessee Psychiatric Associations and is president and founder of Come and Reason Ministries. Dr. Jennings has authored many books, including The God-Shaped Brain, The God-Shaped Heart, and The Aging Brain.
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