Gene Expression

I got interested in vitamin D a few years ago because I was trying to figure out a plausible explanation for why many of the genetic variants implicated in lighter skin seem to have risen in frequency relatively recently, 10,000 years ago, when modern humans have been extant at higher latitudes on the order of 30,000 years. So I started mooting the speculative idea that the switch to agriculture might have reduced vitamin D levels. Initially I assumed that rickets was the main issue, but over the past few years there has been a veritable explosion in the medical literature pointing to correlations between ill health and low vitamin D levels. The proportion of these which are randomized controlled trials are low. Unfortunately, health related topics tend to go through fads, so I’ve not been posting much about vitamin D. But this report is interesting, Study Links Vitamin D, Race and Cardiac Deaths:

Lead author Kevin Fiscella, M.D., said a complex host of genetic and lifestyle factors among blacks may explain why this population group has lower vitamin D levels across the lifespan than other races.

People get vitamin D through their diets, sun exposure, and oral supplements. Genetic factors common to blacks sometimes preclude vitamin D absorption, such as a higher incidence of lactose intolerance, which can eliminate vitamin-D fortified milk from the diet, and darker skin pigment that significantly reduces vitamin D synthesis.

Overall, the analysis showed that, as expected, a vitamin D deficiency was associated with higher rates of death among all people in the sample. In fact, those adults with the worst deficiency had a 40 percent higher risk of death from cardiac illness. This suggests that vitamin D may be a modifiable, independent risk factor for heart disease, Fiscella said.

Most striking, however, was that when researchers adjusted the statistics to look at race, blacks had a 38 percent higher risk of death than whites. As vitamin D levels rose, however, the risk of death was reduced. The same was true when researchers analyzed the effect of poverty on cardiovascular death rates among blacks, which suggests that vitamin D deficiency and poverty each exert separate risk factors, the study said.

The abolition of poverty is going to be a herculean task, but vitamin D supplementation is doable. But even the lead author expresses caution about these sorts of supplementation silver bullets:

Fiscella cautions, however, that not all observational studies of vitamin deficiency are borne out by subsequent clinical trials. For example, previous observational studies of vitamin E and beta-carotene that were associated with poor heart health did not hold up in later clinical studies. The need to further assess the vitamin D connection to heart disease is convincing, however, particularly among blacks, he added.

Slate just published a piece on vitamin crazes. It concludes:

That’s not to say that vitamins aren’t important. Vitamins are critical to all sorts of bodily functions, and we have to get them through diet because our bodies can’t make them on their own. The Office of Dietary Supplements at the NIH recommends that we get certain levels of a variety of kinds of vitamins, and that recommendation is sound. But encouraging us to get a complete suite of vitamins is not the same as suggesting that we get them by popping a pill.

In fact, the reports littering the ODS site seem to converge upon the same point: There is some good news for supplements, but it’s extremely limited. The 2006 NIH panel, for instance, concluded that postmenopausal women should probably take calcium and vitamin D to safeguard their bones; that pregnant women should keep taking folate; and that adults with age-related macular degeneration, an eye disease, should take a combination of antioxidants and zinc. But beyond that, the panel’s strongest recommendation was that scientists conduct further research on the risks and benefits of vitamins. For every study that turns up disconcerting vitamin side effects, there seem to be two more that conclude that we simply don’t know enough yet about supplements to make evidence-based recommendations.

No one doubts the relationship between vitamin D deficiency and rickets at least.

Comments

  1. #1 agnostic
    January 7, 2010

    Vitamin D is fat-soluble, so you need to eat it with fat. And if you’re trying to make it in your skin, Vitamin D is a steroid hormone and so made from cholesterol, so you’ll need plenty of cholesterol. That means the harebrained paranoia against fat and cholesterol will hit dark-skinned people especially hard.

    Vitamins A, E, and K are also fat-soluble and need to be taken with fat. Some anti-oxidants are that way too. That’s one reason why vitamin supplement studies are so muddled. There’s one study showing almost no absorption of beta-carotene (a precursor of vitamin A) when you give people spinach only (spinach is rich in beta-carotene), or with non-fat dressing, but a quantum leap in absorption when you pair spinach with avocado (which is really fatty) or full-fat dressing.

    Vitamin A only comes from liver and animal fat products (like dairy), so most studies done on that are on the pre-cursor carotenoids. So poor results don’t tell us that vitamin A isn’t clearly crucial — it is, for the immune system, epithelial cells, and vision — but that you need to get it from where nature intended you to get it.

    If they’re poor and can’t afford organ meat or butter, they can at least take some cod liver oil. Rich in fat and vitamins A and D:

    http://www.cholesterol-and-health.com/Benefit-Of-Cod-Liver-Oil.html

  2. #2 Jeff
    January 7, 2010

    According to Dr. John Cannell of the Vitamin D Council whites make about 20,000 units of vitamin D within 30 minutes of full body exposure to the sun. He states blacks need 5-10 times longer in the sun to achieve similar vitamin D production.

  3. #3 Kevan Gelling
    January 7, 2010

    Here’s an economist take on the issue from the Political Calculations blog:

    “The Scope of Vitamin D Deficiency in African Americans”

    http://politicalcalculations.blogspot.com/2009/07/scope-of-vitamin-d-deficiency-in.html

  4. #4 omar
    January 7, 2010

    agnostic, while fat is important in getting Vitamin D into your system, intake of cholesterol is not a rate-limiting step in its synthesis in the skin. Microgram quantities are manufactured every day and our intake is in milligrams (as is endogenous synthesis of cholesterol, which is one reason people on low cholesterol diets dont easily lower their serum cholesterol).
    Even people on low cholesterol diets have enough cholesterol to supply the tiny amounts of precursors needed. Total body cholesterol and serum cholesterol are almost never low enough to cause any measurable change in synthesis rates.
    It does seem to have a much broader role in human physiology than was previously known, but I doubt if it is going to be the panacea it is being projected to be by some people.
    In fact, Vitamin D seems to be at some kind of tipping point in the media and I expect that we will soon see some downsides emerging as people jump on the bandwagon and everyone starts to choke on Vitamin D. Having said that, I dont doubt that its an important vitamin and dark skinned people and white people who have bought into the sunscreen hysteria are very likely to be deficient and would be well advised to get some supplements or some sun (in the case of black people, a good deal of sun).

  5. #5 Clark
    January 7, 2010

    I was kind of cautious about vit D as well given all the other past fads. But there really is starting to be a lot of robust literature on it as you say. Plus if you aren’t getting outside enough it can cause problems. Add in the problems of vit D production as you age and I think there’s a compelling case for supplements.

    But as Omar notes, the side effects of supplements haven’t been studied well (or at all). We ought remember some of the past fads.

  6. #6 Paul
    January 8, 2010

    There was an excellent medical article looking at vitamin D levels in relationship to seasonal influenza and a write-up about the article here
    http://healthjournalclub.blogspot.com/2010/01/intruiging-epidemiology-article-part-i.html
    for those interested.

  7. #7 Research
    January 8, 2010

    Hello,

    You really need to look into vitamin D deficiency, brain chemistry and violence/impulse control. Vitamin D affects much more than health, it can shape a culture and a species.

    The smoking gun is that increased serum vitamin D inspires higher levels of the powerful neurotrasmitter serotonin. Serotonin drives;

    …”synthesized in serotonergic neurons in the CNS where it has various functions, including the regulation of mood, appetite, sleep, muscle contraction, libido, impulse control, and some cognitive functions including memory and learning;”…

    What holds chimpanzees back? Impulse control.

    Then look into vitamin D and alopecia (body hair loss);

    …”Hence, alopecia in the VDR-null(cellular vitamin D receptor) mice is due to a defect in epithelial-mesenchymal communication that is required for normal hair cycling.”…

    Vitamin D also affects long bone length and calcium metabolism.

    So vitamin D is tied to all the things that put us ahead of the other great apes, and shape our various cultures. Making this Middle East News no surprise;

    “Burkas Cause Major Vitamin D Deficiency & Hence Breast Cancer”

    A severe case of impulse control would also be found in such cultures devoted to vitamin D deficiency.

    Vitamin D is much more than simply “health”.

  8. #8 toby
    January 9, 2010

    google vitaminD3world for a interesting site. It also has links to a tiny micro tablet formulation of vitamin D

  9. #9 AJohnson
    January 10, 2010

    Very interesting and helpful article. I’m gonna start paying attention how I take my vitamins from now on. Thanks for posting it!

  10. #10 Sandgroper
    January 10, 2010

    Lighter skin arose in modern humans within the last 10,000 years, but earlier in Neanderthals, who never did have agriculture, but a more varied diet than is often assumed.

    It’s puzzling.

  11. #11 Socioprof
    January 10, 2010

    I object to this Racist! article.

    There is nothing biological about race, it is a social construct. Blacks are not getting the Vitamin D they need because of Racist! nutritionists and pharmaceutical employees not educating them properly.

  12. #12 Hoosierville
    January 11, 2010

    The ignorance that abounds on vitamin d deficiency astounds me sometimes. Do the “science” people. The reasearch and results are out there. If you’d like some good info on vitamin d visit these two non-profits to start….oh, and vitamin D is really cheap, or even free…so there’s limited interest in researching it by big Pharma and the Docs.

    http://www.grassrootshealth.org
    and
    http://www.vitamindcouncil.org

  13. #13 Steve
    January 12, 2010

    I would very much like to hear more from and communicate with socioprof/comment #10 to understand his/her views on how nutritionists and drug companies are failing blacks. I can be reached at:
    sschwartz888@yahoo.com

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