Researchers identify racial differences in bone health markers
MedWire News: Results from the US National Health and Nutrition Examination Surveys (NHANES) show that the relationship between 25-hydroxyvitamin D (25[OH]D), bone mineral density (BMD), and parathyroid hormone (PTH) varies by race.
This suggests that "optimal ranges for vitamin D among Whites may not be the same as those among Blacks, at least with respect to optimizing bone and mineral metabolism," remark Orlando Gutiérrez (University of Miami Miller School of Medicine, Florida) and colleagues.
The researchers examined the relationship between 25(OH)D and PTH using data from 8415 adult participants (25% Black, 24% Mexican-American, 51% White) of NHANES 2003-2004 and 2005-2006. They also assessed the relationship between 25(OH)D and BMD among 4206 adult participants (24% Black, 24% Mexican-American, 52% White) in the 2003-2004 sample only.
The team found that Blacks and Mexican-Americans had significantly lower serum 25(OH)D concentrations than Whites, at 14.8 and 19.5 versus 25.6 ng/ml, respectively.
Both groups also had significantly higher PTH concentrations than Whites, at 46.5 and 44.4 versus 39.9 pg/ml, respectively.
BMD was significantly higher among Blacks, at 1.09 cm2, compared with Whites, at 1.02 cm2, but there was no difference in BMD between Mexican-Americans (1.02 cm2) and Whites.
Gutiérrez and team report that BMD significantly decreased with decreasing serum 25(OH)D levels and calcium intake among Whites and Mexican-Americans, but not among Blacks.
In addition, the impact of vitamin D on PTH levels was modified by race/ethnicity. Specifically, PTH was inversely related to 25(OH)D throughout the range of 25(OH)D values in Whites and Mexican-Americans.
In contrast, the inverse relationship between PTH and 25(OH)D in Blacks was only apparent when 25(OH)D values fell below 26 ng/ml. Furthermore, the slope of the relationship between 25(OH)D and PTH was essentially flat above this threshold in Black participants, "suggesting that PTH concentrations may be maximally suppressed at a lower 25(OH)D concentration among Blacks than among Whites or Mexican-Americans," say the authors.
Writing in the journal Osteoporosis International, they conclude that further studies are needed to determine "whether race- and/or ethnic-specific ranges of optimal 25(OH)D are required to appropriately evaluate the adequacy of vitamin D stores in diverse populations."
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By Laura Dean