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TalkingNutrition

Providing perspectives on recent research into vitamins and nutritionals

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Vitamin D Status, Heart Disease, Mortality and Ethnicity

By Michael McBurney

Using 15 years of NHANES data collected from 15,099 adults (≥20y), Sempos and colleagues report that having serum 25(OH)D levels <60 nmol/L significantly increases relative risk (RR) of all-cause mortality. The relationship was strongest in men, women, adults 20 to 64y, and non-Hispanic whites. The NHANES study was too small to evaluate the association in ethnic groups.

Using data collected from 6,436 participants in the Multi-Ethnic Study of Atherosclerosis (MESA), Robinson-Cohen and associates report that low serum 25(OH)D concentrations are associated with increased risk of incident coronary heart disease (CHD) in white [Hazard Ratio (HR) = 1.26 per 25 nmol/L decrement] and Chinese [HR = 1.67] but not black or Hispanic persons.  The median follow-up was 8.5y. Mean serum 25(OH)D concentrations varied by race/ethnicity: White (75.3 nmol/L), Chinese (66.8 nmol/L), black (48 nmol/L), and Hispanic (61.5 nmol/L). Since black individuals seem to have higher circulating 1,25(OH)D concentrations in the presence of lower 25(OH)D concentrations than whites, the authors hypothesize that differences in 25-hydroxyvitamin D-1-α-hdroxylase (CYP27B1) activity may impact vitamin D status in tissues which could explain these racial/ethnic differences.

In an accompanying editorial, Norris and Williams focus on 3 questions about the possible impact of racial/ethnic factors on the relationship between vitamin D status and CHD: 1) Could differences be explained by seasonal variability in 25(OH)D concentrations? 2) Could there be differential regulation of parathyroid hormone (PTH)? 3) Could differential expression of genetic polymorphisms in vitamin D-mediated cellular activation/metabolism explain these results? There is evidence that genetic variations in the vitamin D receptor (VDR) may explain differences in breast cancer risk but the results are inconsistent. Some scientists argue that genetic effects would be more profound in individuals with vitamin D deficiency.

Regardless of race or ethnicity, it makes nutritional sense to maintain sufficient serum 25(OH)D levels(> 50 nmol/L). -mm-

Citations

Sempos CT, Durazo-Arvizu RA, Dawson-Hughes B, Yetley EA, Looker AC, Scheicher RL, Cao G, Burt V, Kramer H, Bailey RL, Dwyer JT, Zhang Z, Gahche J, Coates PM, Picciano MF. Is there a reverse J-shaped association between 25-hydroxyvitamin D and all-cause mortality? Results from the US nationally representative NHANES. 2012 JCEM doi:10.1210/jc.2013-1333

Robinson-Cohen C, Hoofnagle AN, Ix JH, Sachs MC, Tracy RP, Siscovick DS, Kestenbaum BR, de Boer IH. Racial differences in the association of serum 23-hydroxyvitamin D concentration with coronary heart disease events. 2013 JAMA doi:10.1001/jama.2013.7228

Norris KC, Williams SF. Race/ethnicity, serum 25-hydroxyvitamin D, and heart disease. 2013 JAMA doi:10.1001/jama.2013.7229


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