Wednesday, September 26, 2012

The Sun Is Good For You: Part II, Vitamin D and The Vitamin A Synergy Issue

Part I of this series on the sun covered some of the surprising things that you might not yet know about sunlight, such as the fact that major diseases are more prevalent at higher latitudes, as the exposure to UV rays becomes less intense.1 This post covers some of the other issues surrounding vitamin D, which you biosynthesize in your skin from UVB rays, mainly its synergy with another important vitamin, A.

The crux of the issue is don't load up on too much supplemental vitamin A (or any at all), because an overabundance of A could prevent the proper metabolism of vitamin D. I'll let the informative book Primal Body, Primal Mind by Nora Gedgaudas explain the issue in more detail below, but the take away point is strive to get your vitamin A and D from the natural sources for which our bodies are designed.

This means beta carotene from carrots, mangos, and other colorful foods (our intestines convert beta carotene to the amount of preformed vitamin A, retinol, that our bodies need.2), vitamin A from pastured eggs (each one can contain up to a fifth of the RDA for vitamin A), as well as from seafood fats (albeit a smaller source).

Strive to get your vitamin D from the sun, since we biosynthesize it from UVB rays (for those outside the sun belt, like me, obviously we have to get some winter vitamin D from supplements, food like fish, or even small safe doses from a UVB lighting product). Your body will not generate a toxic level of vitamin A from the beta carotene you eat; and neither will your skin produce too much of the fat-soluble vitamin D from the sun.

Now from Primal Body, Primal Mind:

...For each and every receptor for vitamin D, there are two receptors for vitamin A on every cell...A relative balance of these two nutrients is vital to their healthy functioning in the body. An excess of one can create a relative deficiency of the other. For instance, if you take large amounts of vitamin D without vitamin A, you are potentially more likely to develop symptoms of vitamin A deficiency and experience an actual immunosuppressive effect...Recent research from Spain indicates that vitamin A is necessary for both vitamin D binding and vitamin D release to receptor sites. The two vitamins are synergistic and should always be balanced in the diet or in supplementation.3

So what's the blood level of vitamin D that you should strive for? Many people these days have already had their blood tested for vitamin D, or are at least aware of the test. The result is a number, here in the U.S., in nanograms per milliliter (ng/ml). Whereas less than 12 ng/ml is considered by the federal government to be "deficient" and < 20 inadequate for bone and overall health, the Vitamin D Council, among other researchers, given all the new research on the far-reaching health implications for vitamin D, advocates getting the level above 32 to as high as the 50s. Check out this bit of insight on maintaining a level in the 40s from Fitness For Geeks:

A recent study in the British Journal of Nutrition examined the vitamin-D levels of two traditional cultures that live near the equator and spend a lot of time outside— the Maasai and Hadzabe hunter-gatherers of Tanzania in East Africa. The mean vitamin-D level (25( OH) D) in the blood of about 60 study participants, men and women, was 115 nmol, or about 46 ng/ ml, all obtained naturally by exposure to sunlight. The people typically avoided the sun at its strongest, during midday. “Populations with traditional lifestyles having lifelong, year-round exposure to tropical sunlight might provide us with information on optimal vitamin D status from an evolutionary perspective,” according to the study.3

I can relate my own recent experience with vitamin D testing. I paid for a private test from ZRT Lab a few months ago. I had completely gone off my vitamin D supplement, a 4,000 IU soft gel from Carlson, for several months. I was trying to rely on the Spring and Summer sun (along with dietary vitamin D from whole milk, seafood, and whey protein powder), and my level was 33 ng/ml.

This isn't bad for my latitude in New England. I'd like to see it a little higher though, perhaps 40 or a tad above that level, (the test result also is not exact, putting the result somewhere in the range of 29-37 ng/ml, or the like). I went back to the soft gel once or twice a week, and am still getting some sun, then I'll re-test (and let you know what happens).

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

2 Perry, Bruce W. (2012-04-23). Fitness for Geeks: Real Science, Great Nutrition, and Good Health (Kindle Location 3055). OReilly Media - A. Kindle Edition.

3 Gedgaudas, Nora T. (2011-06-22). Primal Body, Primal Mind: Beyond the Paleo Diet for Total Health and a Longer Life (pp. 88-89). Inner Traditions Bear & Company. Kindle Edition.

4 Perry, Bruce W. (2012-04-23). Fitness for Geeks: Real Science, Great Nutrition, and Good Health (Kindle Locations 4795-4800). OReilly Media - A. Kindle Edition.

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