• Myrtle Thierry-Palmer, Veronica M Henderson, Rafiq El Hammali, Stacy Cephas, Cristina Palacios, Berdine R Martin, and Connie M Weaver.
• Department of Biochemistry, Morehouse School of Medicine, 720 Westview Drive SW, Atlanta, GA 30310-1495, USA. mthierry-palmer@msm.edu
• Am. J. Med. Sci. 2008 Apr 1; 335 (4): 278283278-83.

BackgroundThe black American population has a higher prevalence of salt sensitivity compared with the white American population. Dahl salt-sensitive rats, models of salt-induced hypertension, excrete protein-bound vitamin D metabolites into urine, a process that is accelerated during high salt intake. We tested the hypothesis that urinary vitamin D metabolite content and 25-hydroxyvitamin D (25-OHD) binding activity of black female adolescents would be greater than that of white female adolescents.MethodsFemale adolescents (11-15 years old, 11 black and 10 white) were fed low (1.3 g, 56 mmol/24 hours sodium) and high salt (3.86 g, 168 mmol/24 hours sodium) diets for 3 weeks in a randomized order cross-over study design.ResultsWhite and black adolescents had similar mean urinary vitamin D metabolite content (low salt, black versus white: 50 +/- 10 versus 58 +/- 17 pmol/24 hours; high salt, black versus white: 47 +/- 7 versus 79 +/- 16 pmol/24 hours). Mean urinary 25-OHD binding activities of the black and white adolescents did not significantly differ. Urinary 25-OHD binding activity of 10/11 black adolescents and 7/10 white adolescents was greater at week 3 of high salt intake than at week 3 of low salt intake (r = 0.50, P = 0.002, n = 17). Plasma 24,25-dihydroxyvitamin D concentrations of the white female adolescents were significantly higher than that of the black female adolescents (P < 0.001).ConclusionUrinary loss of vitamin D metabolites may be one cause of low vitamin D status, in addition to low dietary intake and reduced skin synthesis.

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