Are you washing your vitamin D down the drain ?

Steve is an engineer, he spends a significant portion of his day on site.  When he is not working, Steve is on his bicycle.  Craig is a card carrying computer geek,vitamin D being washed off spending his days indoors, locked behind his computer.  Craig spends his down time playing with gizmos at home.   Both men live in sunny South Africa.  Both are unpigmented i.e. they are white.   

Both have their vitamin D levels tested as part of a routine medical checkup.  

Who do you expect to fail the test ?  

You probably guessed it would be Craig, because he never sees the sun.  You assumed Steve would be okay.    


The truth is even if you spend time in the sun you could still have low vitamin D

How come ?  

Steve is making the following two “mistakes”.  

  • He smothers himself in sunscreen every time he ventures outside
  • He scrubs himself down every time he comes inside. 

Vitamin D is manufactured in your skin

The outer layer of skin takes cholesterol and converts it to 7-dehydrocholesterol.  The 7-dehydrocholesterol is then secreted into the oil on the skin’s surface.  There it is exposed to ultraviolet light, which provides the energy for a chemical reaction to take place, ending in the formation of cholecalciferol (previtamin D).   

Sunscreen blocks the vitamin D reaction

Smearing a layer of sunblock on your skin, will protect you from turning into a tomatoe, by “blocking” the UV rays which burn the skin.  Unfortunately, the sunscreen also acts as a barrier  for the rays that fuel the vitamin D reaction.  

Soaping up washes vitamin D down the drain

Dipping yourself in water won’t cause the oil + vitamin D combo to wash away, because neither of these chemicals dissolve in water.  But when you reach for the soap, the story changes.  Soaps are fat based which means that fats will dissolve in them, because of the chemistry principle “like dissolves in like”. So as you rub and scrub all over your body, you are washing more than just the dirt  off.  The oil and vitamin D are soluble in fat,  so they will be dissolving in the soap and ultimately running off your body and into the drain. 

 So what should you do ? 

Don’t bath – no, just kidding.   It is no good living a longer happy life, but with no friends, because no one can stand the smell of you.   But lets face it,  “soaping up” is not really a pre-requisite for washing most dirt away.  If you don’t believe me, think about taking a dip in a swimming pool – you emerge pretty clean and odorless.  

So next time you hop in the bath or shower,  think twice before lathering up every nook and cranny.    Judicious use of the soap, could save you a few bucks on the soap bill and improve your vitamin D status.  

Genetic and environmental determinants of vitamin D status. Lancet (2010) 376(9736):148-149. R Bouillon.

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Further reading

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Did you learn something new or do you have a different perspective ? I’d love to hear from you so post me a comment below…..

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  1. By Let the Sunshine vitamin in! « thelittleescape on September 4, 2012 at 7:48 pm

    [...] of oily fish in the diet and its actually hard to imagine that we could get enough!  I also read somewhere that Vitamin D could be washed off your skin before it gets to the deeper layers- yet another [...]

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