Wednesday, August 24, 2016

"Sunlight and Vitamin D: Necessary for Public Health" An Academic Review

And now for something completely different, I'm going to nerd out and share an academic article with you. Don't worry, though, I'll make it painless; you really do need to know about this.

(Note for readers: if you want to reference the study I'm writing about, there are quotes in italics throughout and a link in the next paragraph.  If you just want my summary and opinion, that's in plain text.)

Writing in the recent Journal of the American College of Nutrition, a group of authors have published "Sunlight and Vitamin D: Necessary for PublicHealth."  Head on over if you'd like to geek out on the whole thing, but I'm going to give you the most important points.

Basically, the authors examine the fact that many recommendations from the American Cancer Society, the World Health Organization, and the like, focus on encouraging sun avoidance and sunscreen use during the very hours of the day that our bodies are most primed to make use of the sun:

"Though these recommendations, all focused on reduction of skin cancer, are accompanied by brief acknowledgement of the importance of vitamin D for health, they persist in urging avoidance of the sun at the precise times when vitamin D can be synthesized in the skin—the hours between 10 am and 3 pm—and suggest that all necessary vitamin D can be obtained through food and dietary supplements."

And yet, there are compelling reasons to get your Vitamin D from the sun. Take a look at this introductory paragraph:

"These recommendations are understandable from the viewpoint of preventing the 3.5 million new cases of and 2000 deaths from nonmelanoma skin cancer in the United States each year, but they neglect the fact that we have a long cultural history of appreciation of the sun and use of UV radiation for healing purposes. Moreover, they neglect that we have evolved with physiological adaptations to help protect the skin from the sun when we are mindful of our exposure and do not burn. They neglect the fact that increased sun exposure, based on latitude, has been associated with protection from several different types of cancer, type 1 diabetes, multiple sclerosis, and other diseases. They also neglect the fact that exposure to the sun induces beneficial physiological changes beyond the production of vitamin D. Though adherence to the current sun-protective recommendations would likely result in the reduction of nonmelanoma skin cancer, that reduction would likely be overshadowed by the potential reduction in deaths from other cancers and from cardiovascular disease, which could be achieved by doubling average blood concentrations of 25-hydroxyvitamin D (25(OH)D) to 40 ng/mL through a combination of sun exposure and supplements."

Let's break that down a bit.  Basically, we're saying that, in our zeal to protect ourselves from approximately 2000 nonmelanoma skin cancer deaths a year, we are turning our backs (no pun intended) on our cultural and biological adaptations that allow us to appreciate the sun and use it for healing. Additionally, we are increasing our risk of other types of cancer, type 1 diabetes, multiple sclerosis, and other conditions.

For example, look at these benefits:

"When the skin is stimulated with UVA radiation, nitric oxide is released, stimulating vasodilation and lowering of blood pressure. During active exposure to UVA, diastolic blood pressure in one study fell by roughly 5 mmHg and remained lower for 30 minutes after exposure. A reduction of diastolic blood pressure by 5 mmHg decreases risk for stroke by 34% and coronary heart disease by 21%."

"Additionally, human skin produces beta-endorphin in response to UVB exposure; these opioid peptides have the result of increasing a feeling of well-being, boosting the immune system, relieving pain, promoting relaxation, wound healing, and cellular differentiation. Light signals received through the eye regulate production of melatonin and serotonin for circadian rhythm control and also play a role in seasonal affective disorder."

Short form: sunlight contains both UVA and UVB radiation.  The UVA radiation can lower blood pressure enough to decrease risk for stroke and coronary heart disease. UVB radiation can improve mood, help with certain depressive conditions, improve the immune system, relieve pain, and help with healing.

Are we sure we want to keep avoiding the sun?

Look, no one is going to tell you to go try to get a sunburn. And if vitamin D supplements make sense to you, go for it.  But the sun has been getting a bad rap lately.

And, there are reasons for seeking the sun:

"The full solar spectrum is essential to optimal health and well-being. Humans are physiologically adapted to produce vitamin D in response to sun exposure, specifically UVB radiation; other regions of the spectrum seem to confer benefit as well. Though some vitamin D comes from our diet (and more recently from supplements), we should not ignore the natural capacity that we possess to produce our own. We are of the opinion that moderate sun exposure (less than the time required to burn) to the arms, shoulders, trunk, and legs should be sought rather than avoided."

I agree with the authors.  Bottom line, the full spectrum of sunlight seems to confer many health benefits, and our bodies are designed to make vitamin D from this exposure. So go outside wearing a tank top and shorts. Mow the lawn, hang the laundry, take a bike ride. Do so between the hours of 10 am and 3 pm for maximum formation of vitamin D.  As long as you don't allow yourself to burn, you will very likely be helping your health far more than you might possibly harm it.

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