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Black seniors near equator: increased vitamin D decreases bone density – Sept 2011

The association of serum 25-hydroxyvitamin D with indicators of bone quality in men of Caucasian and African ancestry.

Osteoporos Int. 2011 Sep;22(9):2475-85. Epub 2010 Nov 23.
Barbour KE, Zmuda JM, Horwitz MJ, Strotmeyer ES, Boudreau R, Evans RW, Ensrud KE, Gordon CL, Petit MA, Patrick AL, Cauley JA; Osteoporotic Fractures in Men (MrOS) Research Group.
Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA, USA. barbourk at edc.pitt.edu

We examined the association of serum 25-hydroxyvitamin D 25(OH)D with indices of bone quality in older men. Positive associations for 25(OH)D and bone mineral density, content, cortical thickness, and axial and polar strength strain indices were observed among Caucasians; however, among men of African descent findings were either null or negative.

INTRODUCTION:

There are limited data on serum 25(OH)D and bone measures in men of African ancestry. To better understand racial differences in vitamin D status and bone health, a cross-sectional study among 446 Caucasian men in the US and 496 men of African ancestry in Tobago (age ? 65 years) was conducted.

(Note: Tobago is only 11 degrees away from Equator)

METHODS:

Serum 25(OH)D (liquid chromatography and tandem mass spectrometry) was measured, and peripheral quantitative computed tomography scans were administered. Bone measures estimated included trabecular and cortical volumetric bone mineral density (vBMD), bone mineral content (BMC), bone geometry (cross-sectional area and cortical thickness), and polar and axial strength strain indices (SSIp and SSIx).

RESULTS:

Men of African ancestry had higher 25(OH)D than Caucasians (34.7 vs. 27.6 ng/ml, p < 0.01).

Among Caucasians, 25(OH)D was positively (p trend < 0.05) associated with cortical vBMD, total BMC, cortical thickness, SSIp, and SSIx at the distal radius after adjustment for potential confounders. Similar patterns were observed at the distal tibia.

In contrast, in men of African ancestry, there was an inverse association (p trend < 0.05) between 25(OH)D and the cross-sectional area, and SSIx.

Race modified (p for interaction < 0.05) the association between 25(OH)D and total BMC, cross-sectional area, SSIp, SSIx, and trabecular vBMD of the radius.

In men of African ancestry, there was evidence of a threshold effect (at approximately 18 ng/ml) for 25(OH)D on tibial total BMC and cortical thickness.

CONCLUSIONS:

More studies are needed to better comprehend these race differences for 25(OH)D and bone density, geometry, and indices of bone strength.

PMID: 21104232
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Comment at VitaminDWiki: Strange, wonder if it has anything to do with being close to the equator

See also VitaminDWiki


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