Gene Expression

Vitamin D does a body good

I’ve spoken about Vitamin D a fair amount on this blog before. Not only have I presented it as a major selective pressure for light skin in the northern latitudes after the switch to agricultural lifestyles (and the concomitant nutrient deprivations due to reliance on a predominantly starch diet), but I recently found that I myself suffered from a lack. Though I eat a salad most days, and try to eat meats and fish, the fact that I have dark skin and live at a relatively high latitude and in a region characterized by cloudy winters was a combination which naturally led to low levels of synthesis. I’m taking supplements now, and plan on taking them for a long time.

After I found out about my own deficiency I looked up some side effects. You all know about Rickets, but it turned out there were a host of global low level ailments that might be correlated with a lack of this nutrient. Now more evidence, Vitamin D Supplements Appear To Be Associated With Lower Risk Of Death:

Past studies have suggested that deficiencies in vitamin D might be associated with a higher risk of death from cancer, heart disease and diabetes–illnesses that account for 60 percent to 70 percent of deaths in high-income nations, according to background information in the article. “If the associations made between vitamin D and these conditions were consistent, then interventions effectively strengthening vitamin D status should result in reduced total mortality,” the authors write.

Over an average follow-up period of 5.7 years, 4,777 of the participants died. Individuals who took vitamin D had a 7 percent lower risk of death than those who did not. In the nine trials that collected blood samples, those who took supplements had an average 1.4- to 5.2-fold higher blood level of vitamin D than those who did not.

Of course, many of the diseases above hit late in life; evolutionarily they might not have been particularly salient (though I doubt that matters to do you if you are 65 and looking at a few extra healthy years). But I suspect that increased morbidity is simply the margin here, it probably has a non-trivial effect on basal physiological fitness.

Comments

  1. #1 John Emerson
    September 14, 2007

    Vitamin D and A are the vitamins with toxic doses, however. Moderation!

  2. #2 Jill Sylvan
    September 14, 2007

    Would vitamin D deficiency in a young adult perhaps be one of the causes of acne?

  3. #3 Biff
    September 14, 2007

    More salient evolutionarily might be recent findings regarding pre-eclampsia. Also, there is thin but growing evidence that vitamin D confers resistance to tuberculosis and other infections such as influenza.

  4. #4 Pelican's Point
    September 15, 2007

    I spent a lot of time in the sun when I was young – surfing, mtn climbing, beach volleyball, etc. My doctor removed a basal cell carcinoma a few years ago. I go in for annual skin checkups now.

    Like for many older folks my doctor has recommended strict use of sun block, hats and caps, staying our of bright sun, etc. While perhaps saving me from melanoma could those things contribute to other cancers by contributing to Vit D deficiency maybe?

  5. #5 MarkH
    December 26, 2007

    I wouldn’t call that evidence thin biff. The role of vitamin D in tuberculosis was actually pretty well nailed by studies of immigrants in the UK which demonstrate that latent TB infections will reactivate in the sunless climate. The demonstration of the role of Vit D in making defensins seems the likely physiological explanation.

    I am wary though of some of the more hyperbolic claims I’ve seen about vitamin D lately. It’s fascinating stuff, sure. But until replicated in RCT rather than epidemiologically I think it’s too early to recommend universal supplementation with a vitamin that does have a toxic syndrome. Many vitamins have appeared similarly astounding in such studies and the benefits failed to pan out. This is likely due to certain epidemiologic biases that tend to show people who actively take care of themselves (take supplements, exercise, etc.) are generally wealthier, and healthier.

    Certainly deficiency is a problem though, and it’s really under-recognized. It’s also all the dermatologists fault, telling use to stay out of the sun, when we do need some sun in moderation. Just no burns.

  6. #6 Biff
    December 27, 2007

    “I wouldn’t call that evidence thin biff. The role of vitamin D in tuberculosis was actually pretty well nailed by studies of immigrants in the UK which demonstrate that latent TB infections will reactivate in the sunless climate.”

    “But until replicated in RCT rather than epidemiologically I think it’s too early to…”

    I’m having a hard time reconciling the two quotes above. First you seem to be claiming epidemiological studies provide strong evidence, then in the next paragraph you suggest that epidemiological studies shouldn’t be taken too seriously because they are a weak form of evidence. Methinks I detect a bit of confirmation bias.