Friday, December 24, 2010

Everything We Thought We Knew About Vitamin D And Latitude Might Be Wrong!

by Chris Masterjohn

New blog post over at WestonAPrice.Org on why everything we thought we knew about vitamin D and latitude might be wrong:

Vitamin D -- Problems With the Latitude Hypothesis

Read more about the author, Chris Masterjohn, PhD, here.

5 comments:

  1. It seems to me that one extremely important factor is left out from the latitude studies. For example, if you compare middle-class Brazilians with middle class Germans, the latitude effect might be greatly diminished by the Brazilians similar propensity to work and live indoors and travel by closed vehicles (and wear clothing & use sunscreen). The total amount of UV one receives could be well much more correlated with total time spent outdoors. If this was indeed the case, then that would explain why Caucasians with lighter skins have better vitD status. Obviously hominid ancestors have often sought refuge from the sun (just like basically all tropical and subtropical mammals!), but their total UV exposure still had to be enormously greater than that of contemporary folk living in somewhat civilized condition, e.g. with no need to hunt for game or forage in the wilderness.

    I will be more eager to update beliefs on a VitD serum study if it controlled for time spent outdoors and/or included tropical hunter-gatherer subjects or detailed anthropological considerations for ancestral sun exposure.

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  2. Andras, I agree. My point is not that these data provide a definitive demonstration that latitude is not important, but that they provide reasons to question it, and highlight just how tenuous our beliefs about vitamin D and latitude are.

    "Enormously greater"? I doubt it. As I pointed out in the first 2/3 of the post, newer evidence suggests that even in the article circle tropical levels of vitamin D production are available for eight months of the year. Not with clothing, obviously, but like you say, our ancestors likely took refuge from the sun like all mammals.

    Chris

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  3. Water was a critical factor why people covered themselves. Conservation of body fluid is the reason herders, farmers and hunters who weren't under tree cover draped themselves. Versatility was inherent in a swath that could be shifted around to match day's effect on skin.

    1 gallon of water weighs 8 pounds and isn't always "on tap" for outdoors activity. Haitian tropical field laborers swinging a pick all day still prefer long sleeves and to ration water carried. Rice planting women cover up because they won't drink paddy water more than vanity.

    Modesty (as an explanation of clothing) doesn't account for some tribal woman who lifted their "dress" to cover their face from strangers. Trade in textile/cloth/hide was important to primitive cultures for body fluid conservation not originally aesthetics.

    Color was important; the Berbers kept it dark. White clothing, lack of color, is a settled community indulgence people used to identify themselves as "beyond" grunt labor.

    Freezing latitudes change the reason for clothing. Incredibly those indigenous Tasmanians and Tierra del Fuegoans still showed a lot of cold skin.

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  4. Tropical islanders don't always inhabit one with unlimited fresh water. The Polynesians were adventurers who knew they needed water. The original voyagers didn't have 5 gallon buckets to stow; a squall is only good if it's falling on top of you.

    Coconut greased skin filled your pores and they don't evaporate off fluid as quickly. It would have been empirical knowledge to Polynesians. When they got to a new island they used what worked to get them there.

    On land in tropical storms I see adults take cover and laugh at the kids stomping puddles out in the rain. W. Price probably was being teased as gullible when told oiled skin was important for quick drying off. Native people everywhere always think we outsiders ask dumb questions, are denser than them and are less fun.

    The clothing optional lifestyle also left more skin surface to be scratched. The anti-infective effect of the coco oil would have become part of folk medicine. They rejected cloth covering because in the humidity it propogates mildew, smells and chaffes; the old way worked fine.

    Skin anatomy is fairly simple in how it responds to sun. The hydration from coco grease was directly observable for avoiding skin roughening. Polynesians were not keen on sucking tongue, but they knew the pleasure of bumping the uglies with a smooth partner.

    Scientificly there aren't a lot of native descriptive nuances. By avoiding dehydration inside and out they functioned better. The oil "fed" them - if you didn't know, and had to ask.

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  5. From a non-scientific point of view - I really like the vision of our skin performing a photosynthesis type activity to create what seems to be a previously "unknown" powerful healing hormone in Vit D.
    Whether the latitude theory holds true or not, I look forward to more detail about how Vit D really is created. And your challenging the conclusions made by scientific studies out there, certainly makes for interesting debate!

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