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Information on the latest vitamin D news and research.

Find out more information on deficiency, supplementation, sun exposure, and how vitamin D relates to your health.

New study suggests vitamin D deficiency linked to increased stroke risk

On February 2nd, researchers at the University of Alabama announced that sunlight is inversely associated with stroke: the more sunlight the fewer strokes. The authors also commented on the poor wisdom of avoiding all sunlight; that is, they implied the dermatologists have done us harm.

Lack of Sunlight May Raise Stroke Risk

Strokes are the third leading cause of death in the USA, but the leading cause of disability. High blood pressure is the single most important modifiable medical risk factor, but inflammation (as measured by CRP) and diabetes are major medical risk factors as well. Blacks are twice as likely as Whites to suffer a stroke, even after scientists account for all the socioeconomic and medical risk factors. Why do so many more Blacks die from strokes as Whites?

It is not vitamin D, according to Dr. Erin Michos and colleagues in a paper just published in the journal Nutrition. However, the researchers found that vitamin D levels were a major risk factor for Whites but not for Blacks. Whites with low vitamin D levels (<15 ng/ml) had a threefold higher risk for stroke compared to Whites with higher levels. This is one of those studies where they collected blood in the late 1980s and early 1990s, froze it, and then waited to see who died of what and when over the next 14 years.

Michos ED, et al. 25-Hydroxyvitamin D deficiency is associated with fatal stroke among whites but not blacks: The NHANES-III linked mortality files. Nutrition. 2012 Jan 18. [Epub ahead of print]

For Whites, all the traditional risk factors were strongly influenced by 25(OH)D levels (p= <0.0001) including, you guessed it, CRP. For Whites in the highest quartile of vitamin D levels (mean = 44 ng/ml), they had much lower CRP (.35 vs. .48), less diabetes (4.1 % vs. 8.9%), less hypertension (22% vs. 35%) and less cholesterol problems (22% vs. 31%) than the Whites in the lowest quartile of vitamin D (mean=17 ng/ml). They could not find similar robust finding for Blacks, and they hypothesized that perhaps Blacks can get along with less vitamin D than Whites can. That certainly does not appear to be the case in equatorial Africa.

I suspect they couldn’t find the relationship here because American Blacks have such low vitamin D levels, that the range in blood levels is not large enough to show clinical or statistical significance. That is, so many American Blacks are deficient and at risk of stroke, the number with vitamin D levels high enough to help prevent stroke are negligible. As I said, the authors note another possibility, that vitamin D metabolism is different in Blacks. Although possible, I think it’s best to treat the massive deficiency in the Black community first. I suspect researchers will find that deficiency is deficiency, no matter the skin color.

  About: John Cannell, MD

Dr. John Cannell is founder of the Vitamin D Council. He has written many peer-reviewed papers on vitamin D and speaks frequently across the United States on the subject. Dr. Cannell holds an M.D. and has served the medical field as a general practitioner, emergency physician, and psychiatrist.

3 Responses to New study suggests vitamin D deficiency linked to increased stroke risk

  1. Ian says:

    My German is not too good so this abstract from Eurekalert will do.

    Contact: Dr. med. Stefan Schilling
    Deutsches Aerzteblatt International
    Vitamin D deficiency in geriatric patients

    The great majority of geriatric patients in a German rehabilitation hospital were found to have vitamin D deficiency. Stefan Schilling presents his study results in this week’s issue of Deutsches Ärzteblatt International (Dtsch Arztebl Int 2012; 109[3]: 33-8).

    In order to establish the vitamin D status in geriatric patients in Germany, the researchers measured 25-OH vitamin D in 1578 patients in the geriatric rehabilitation hospital in Trier after they had been examined on admission.

    Insufficiently high concentrations were found in 89% of patients, and 67% had severe vitamin D deficiency. Vitamin D affects the calcium and bone metabolism, and it is also attributed with numerous other effects. A sufficiently high concentration of vitamin D, and its effects on the muscles, seems to help reduce the risk of falls and thus of fractures.

    Older people seek exposure to the sun less often than young people; the risk of skin cancer is another reason for restricting sun exposure. In contrast to the fluctuations in vitamin D levels between the summer and winter halves of the year that is observed in young people, the old patients in this study (average age 82) did not display any seasonal fluctuations.

    According to the recommendations of the Institute of Medicine, daily supplementation with 800 IU of vitamin D is therefore advisable in people older than 70.

  2. Dan says:

    What about the effect of diet on acid generation causing acidosis? It would seem that Vitamin D and good diet go hand in hand.

  3. Brant Cebulla says:

    Dan, can you elaborate a little further? What do you mean by “it would seem that vitamin D and good diet go hand in hand”?