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Washing away vitamin D

Posted on: January 31, 2012   by  John Cannell, MD


The recent Netherlands paper on “natural” vitamin D levels in Africa immediately brought to my mind another paper, a similar attempt to gather this vital information. If we don’t know what our vitamin D levels were during the two million years our species was evolving, then how do we know what level to achieve while we wait for science to complete its work?

Binkley N, et al. Low vitamin D status despite abundant sun exposure. J Clin Endocrinol Metab. 2007 Jun;92(6):2130-5. Epub 2007 Apr 10.

Professor Binkley and his colleagues found that surfers and skate-boarders in Hawaii had levels around 30 ng/ml with the highest level being 60 ng/ml. Why would light-skinned sun-drenched outdoor sport enthusiasts in Hawaii have an average level of 30 ng/ml, while very dark-skinned hunter-gatherers in Africa have levels of 50 ng/ml?

Sunscreen is one possibility, but 40% of Binkley et al’s subjects reported never using sunscreen, and the rest were not obsessive about using it. Essentially, all of Binkley et als’ subjects had evidence of abundant sun-exposure, indicating that the author’s calculation that they obtained the equivalent of 11 hours of full-body sun exposure per week with no sunscreen was correct. If not sunscreen, then what could explain the difference between Hawaii and Africa? Genetics is a possibility, as about 40% of vitamin D levels are heritable, but if genetics was the answer, why would the highest levels be in subjects living on the equator, where sun can so easily do the job?

What about latitude? The Africans were at latitude 3 degrees while the “A’ala Park Board Shop” in Hawaii is at latitude 21 degrees. That may explain some of it, although the sun in Hawaii gets very high in the sky, even in March. Anyway, the hunter-gatherers in Africa regularly avoided activity during midday, planning their foraging and hunting trips in the morning or evening.

The only other possibility I can think of is an obscure paper from 1937, a paper that continues to be ignored. The authors obtained surface oils from young men, sebum. In the first experiment, they irradiated the oils and in a second experiment irradiated the young men. They collected the sebum and showed that irradiated sebum cured rickets in rats (showing effective treatment of rachitic rats was the only way of measuring vitamin D activity in 1937). The authors concluded, “The evidence presented in the two groups of experiments indicates that washing the human skin by the usual methods removes vitamin D and its precursors from the outer layer of the skin.”

Helmer AC, Jensen CH: Vitamin D precursors removed from the skin by washing. Studies Inst Divi Thomae 1937, 1:207-216.

Even more upsetting, they concluded, “There is definitive evidence that the secretions from the skin contains precursors of vitamin D, which after irradiation are to be reabsorbed by the body, and the removal of which tends to produce a dearth of the vitamin unless it be supplied in some other form.” I could not see evidence that they supported this statement with their research. What they showed was simple.

Humans make some vitamin D on the surface of their skin, which water washes off. How much humans make on the surface and how much inside the skin, no one knows. However, the vitamin D levels of the African tribesmen support (but do not prove) the proposition that humans living in a natural state make a significant proportion of vitamin D on the surface of their skin for later absorption. Assuming the African hunter-gatherers do not take  showers twice a day that so many cosmetically brainwashed Americans do, then simple water, especially soapy water, routinely washes off oils containing vitamin D in modern humans. This means we must add soap and frequent showering to the list of things that explain why modern vitamin D levels continue to decline, decade after decade.

12 Responses to Washing away vitamin D

  1. [email protected]

    This blog post is cut off with an ominous warning “Sorry but you do not have access to this post/page. Please review your membership here No access.”. I’m sure my membership is up to date, and I can access every other blog post. Please clarify.

    • Brant Cebulla

      Issue is fixed, thanks Roger.

  2. [email protected]

    Thanks for fixing your technical problem. It works fine now.

  3. cwnielson

    Is it possible surfing itself washes off the relevant oils?

    • Brant Cebulla

      This is a question of mine as well, cwnielson.

  4. Frederica Huxley

    This begs the question – how long does it take for the skin to absorb the precursor to Vitamin D? 12 hrs, 24hrs, or days?

  5. Brant Cebulla


    Skin first produces previtamin D3 in plasma membranes of skin cells, and about 50% of this previtamin D3 is converted to vitamin D3 within 2 hours.

    Holick M. “Photobiology of Vitamin D” Vitamin D: Second Edition, Chapter 3. 2005.

    Body begins converting vitamin D3 from the skin to 25(OH)D at 10 hours, with 25(OH)D levels peaking at 24 hours.


    This second paper is a great read, highly recommend, and it is open access.

  6. donnafickel

    Thanks Brant for clarifying the time period. Perhaps a 24 wait before taking a shower after a therapeutic sun bath is ok?

  7. [email protected]

    Being a dogowner all my life, I have to ask; when I´ve been out in the sun all day, (remember that Sweden has too little of summermonths with sun) … the sun is shining, it´s just fantastic, you really feel “sun-kissed” and blessed, and the skin has a film of sweat, what happens? the dogs always came and licked the sweat away. I thought it was about the salt, for many years, but now I think it might be the vitamin D. What do you say?

  8. sebrooks66690200

    Interesting. So this conclusion is based on the hypothesis that we can wash vitamin D off our skin because dark-skinned African hunters have the optimal levels of vitamin D (50ng/ml) while light-skinned sport enthusiast “only” have “sufficient” levels of vitamin D (30ng/ml)??? Rational… In 1937 researchers concluded that you can wash vitamin D off your skin because they were able to abstract surface oils from the skin which cured rickets in rats. Interesting. They didn’t test to see if the vitamin D was both absorbed and also available on the skin. Today we know that vitamin D is immediately adsorbed in the living cells of our skin mainly the epidermis (A leading Guru on vitamin D, Michael Holick). We also know that we need UVB rays to make the vitamin D in the skin (exposure at the right time). We also know that you cannot become toxic from the sun… Because your body knows when to stop making the D. What was not discussed was whether or not the African hunters who are exposed to the sun also eat a high rich diet of oily fish which would increase their levels (through supplementation).
    If you are out in the sun “a lot” it does not mean you are going to get your vitamin D. What we need to know is the time that the UVB rays are coming through. There are certain times of the year where you could lay outside 24/7 with no clothing and no clouds and get “0” vitamin D.
    My best, Stephanie

  9. rittertempel

    This is the most proffesional men of the world. He checked the sebum on the skin but I don’t checked if the water which was used for the shower contains sebum. Very good!

  10. Vannie

    I’m curious. If vitamin D is formed on the surface of the skin, in the sebum, how does the colour of the skin make any difference to that? Surely the sebum is colourless and can therefore react with the UVB rays whether or not the person has dark or light skin?

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