[re-posted from the "Odds and Ends" forum; probably more appropriate here]
Does anyone know of studies that verify Dr Mercola's claim that soap and chlorine strip away and destroy Vitamin D production via sunlight on the skin? I like getting out in the pool/hot tub while I get my natural VitD, but I usually have a shower with soap afterwards to rinse off all the chlorine. When I simply sunbathe without getting in the pool I just shower off with water afterwards.
It'd be a shame if it's true that chlorine and soap "undo" the positives of sun exposure because as we all know, spending time in water is as primal as it gets, but not everyone happens to live near a nice clean river.
Google finds the article. Here 'tis:
Shocking Update Sunshine Can Actually Decrease Your Vitamin D Levels
Here's the nub of the argument:
It sounds plausible.vitamin D3 is an oil soluble steroid hormone. It’s formed when your skin is exposed to ultraviolet B (UVB) radiation from the sun (or a safe tanning bed). When UVB strikes the surface of your skin, your skin converts a cholesterol derivative in your skin into vitamin D3. [my emphasis]
The critical question then is: how long does it take the vitamin D3 to penetrate your skin and reach your bloodstream?
If you’re thinking about an hour or two, like I did until recently, you’re wrong. Because new evidence shows it takes up to 48 hours before you absorb the majority of the vitamin D that was generated by exposing your skin to the sun!
Therefore, if you shower with soap, you will simply wash away much of the vitamin D3 your skin generated ...
Where's Mercola getting this from? From personal communication by the sound of it. He says:
it sounds as though so far as (possible) support for this claim goes you'll have to wait till later this year. I took a quick look in pubmed:Dr. Cannell will actually be publishing a paper specifically detailing this position later this year.
Home - PubMed - NCBI
I tried "vitamin d skin chlorine". No returns. Nor can I see anything relevant when trying "vitamin d chlorine" as a search term. And "vitamin d soap" gets nothing relevant.
I guess no-one has thought to look into this before, and the team that has done so hasn't yet published.
I should think that in the meantime those who want to play safe could follow Mercola's advice:
But maybe if you've been in chlorinated water, you'd want to wash pretty thoroughly.However you really only need to use soap underneath your arms and your groin area. , so this is not a major hygiene issue. You’ll just want to avoid soaping up the larger areas of your body that were exposed to the sun.
I think anyone who's worried about their vitamin D status should, in any case, have a blood-spot test done.
Sorry, I should add: Soap is a surfactant (SURFace ACTive AgeNT). Oil and water don't mix, as you'll know. But the presence of the surfactant (soap) does allow that to happen: hence soap will help you wash off dirt. The relevant point here is that the D3 is "oil soluble" (which is why I emphasised those words in the original). Hence water on its own would not be a problem, but perhaps soap-and-water could be.
Last edited by Lewis; 10-15-2013 at 10:54 AM.