Monday, September 10, 2012

The Sun Is Good For You, Imagine That: Part 1

As the sun fades ever so slowly here in the northern latitudes where I live, I'm still trying to get a reasonably healthy dose of natural sunlight, as in swimming, reading, and hiking/running around in the morning sun (prior to 10-11am), and maintaining a light tan. No sun burns! This is healthy in surprising ways that we usually don't think about, as in having "Aha" moments when you find out that sunlight can release beta endorphins and even lower blood pressure ("no wonder I always feel better after being out in the sun.").

Humans have used the sun for therapy for centuries (in ancient China, Greece, and Rome, for instance). Similar to fasting, however, the over-dependence on pharmaceutical solutions for dealing with the symptoms of ill health has pushed the simple preventive remedies such "getting enough sunlight" out of the picture (no pun intended). Of course, overexposure to sunlight can have some negative effects – so be judicious but not sun phobic.

How much is too much?

For most white people, a half-hour in the summer sun in a bathing suit can initiate the release of 50,000 IU (1.25 mg) vitamin D into the circulation within 24 hours of exposure; this same amount of exposure yields 20,000–30,000 IU in tanned individuals and 8,000–10,000 IU in dark-skinned people.1

Remember that sun exposure involves two types of UV rays based on their differing wavelengths; UVA (320-400 nm.) and UVB (290-320 nm.). UVC rays (100-290 nm.) are "completely absorbed by the ozone layer and atmosphere".

"UVB-induced tanning is located in the upper layers of the epidermis, while UVA-induced tanning is primary localized in the basal cell layer." (See the cited article below.)

It seems like everyone has at least heard about vitamin D and the sun connection. An April 2012 scientific review of the health benefits conferred by ultraviolet (UV) radiation – "Beneficial effects of UV radiation other than via vitamin D production" – pointed out a number of positive features of sunlight exposure that I find intuitive (because we evolved outside in the sunshine) and surprising. Here are some not all of them.

(1) Seemingly all the major diseases that befall humanity increase with latitude, meaning that there may be a link between disease incidence and getting a lower dose of UV radiation the farther north of the equator a person lives. Vitamin D deficiency, since we biosynthesize vitamin D from the sun, is the suspected culprit.

However "it is possible that the reported protective effect of sunlight on the mentioned types of cancer and other diseases are not mediated only through vitamin D but also through other and as yet unknown mechanisms...A few years ago Becklund et al. demonstrated that vitamin D supplementation is less efficient than UV radiation in suppressing multiple sclerosis in animals."

The risk and/or mortality of autoimmune diseases (multiple sclerosis, asthma and type 1 diabetes mellitus), cardiovascular diseases (hypertension and myocardial infarction), several cancers (bladder, breast, cervical, colon, endometrial, esophageal, gastric, lung, ovarian, pancreatic, rectal, renal and vulvar cancer) and other conditions increases with latitude (decreasing UV dose) of residence... Generally, it is believed that the increased risk of these diseases is due to lack of UVB radiation which leads to vitamin D deficiency. No mechanism other than vitamin D production has been proposed to explain the effects of UVB exposure on reducing these disease risk

(2) Sun exposure can lower blood pressure and may improve overall cardiovascular health. The skin includes a large reservoir of nitric oxide (NO), which is released by sun or UV exposure into the bloodstream. The liberated NO may dilate blood vessels and help lower blood pressure.

(3) Basking in the sunlight gives you the equivalent of a runner's high. Hey, it feels good, so what should be so shocking about that? Not all things that "feel good" temporarily are healthy, but in this case we may be able to draw that common-sense conclusion.

Exposure to sunlight has been linked to improved energy and elevated mood...exposure of keratinocytes to UV radiation leads to production of an opioid β-endorphin via stimulation of the POMC promoter. This β-endorphin released into the blood during UV exposure may reach the brain in sufficient concentrations to induce mood enhancement and relaxation

(4) Basking in the sun can help heal wounds.

It has been proposed that UVA-induced NO2 (a derivative of the nitric oxide) may also have antimicrobial effects, be involved in cutaneous wound healing as well as have antitumor activity.

As I'll point out in Part II of these posts, generating vitamin D from the sun is in many instances superior to getting vitamin D from supplements.

Source: "Beneficial effects of UV radiation other than via vitamin D production"; http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3427189/?tool=pmcentrez

And if you don't mind looking at scientific references and literature, here are a few other resources:

1"Benefits of Sunlight: A Bright Spot for Human Health"; http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2290997/

"Vitamin D: The “sunshine” vitamin"; http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3356951/?tool=pmcentrez

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