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Bioavailable Vitamin D is the same blacks and whites, but measured vit D is not – Oct 2014

Total Vitamin D (standard measure) = 1+2+3

  1. bio-available D
  2. D tied up with albumin D
  3. D tied up with D binding protein
VitaminDWiki Summary

Currently total vitamin D is measured, and the bio-available vitamin D is estimated
Estimation of bio-available is based on Vitamin D binding protein (VDB) and albumiN32
VDB varies with race and other factors
Bio-available vitamin D is currently difficult to measure, but there are some possibilities
See also VitaminDWiki

The articles in Vikamin D Binding Protein and Darker Skin are here:

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24,25-Dihydroxyvitamin d3 and vitamin D status of community-dwelling black and white Americans.
Clin Chem. 2015 Jun;61(6):877-84. doi: 10.1373/clinchem.2015.240051. Epub 2015 Apr 28.
Berg AH1, Powe CE2, Evans MK3, Wenger J4, Ortiz G4, Zonderman AB3, Suntharalingam P5, Lucchesi K4, Powe NR6, Karumanchi SA7, Thadhani RI8.

24,25-Dihydroxyvitamin D [24,25(OH)2D] is a metabolite of 25-hydroxyvitamin D (25D). Blacks frequently have low total 25D without manifestations of vitamin D deficiency, suggesting that total serum 25D may incorrectly reflect vitamin D status in different racial groups. The ratio of serum 24,25(OH)2D to 25D [vitamin D metabolite ratio (VMR)] represents a new candidate biomarker for vitamin D status.

We measured 24,25(OH)2D3 and 25D3 by mass spectrometry in a random community cohort of black (n = 212) and white (n = 164) Americans to evaluate VMR as a marker for vitamin D status. We measured parathyroid hormone concentrations by immunoassay to compare VMR and 25D3 against a physiological indicator of vitamin D deficiency.

Serum 24,25(OH)2D3 strongly correlated with 25D3 in both black and white study participants (r = 0.90, P < 0.001 and r = 0.86, P < 0.001 respectively). Blacks had lower mean 25D3 than whites [17.0 (7.8) vs 27.5 (11.3) ng/mL; 42.4 (19.5) vs 68.6 (28.2) nmol/L, P < 0.001] and lower mean 24,25(OH)2D3 [2.1 (1.3) vs 3.6 (2.0) ng/mL; 5.1 (3.1) vs 8.7 (4.8) nmol/L, P < 0.001]. In contrast to total 25D3 concentrations, mean VMR values were similar in blacks and whites [11.9 (4.0) vs 12.5 (3.4), P = 0.16, respectively] and were negatively correlated with parathyroid hormone concentrations in both races (rs = -0.26, P < 0.001, and rs = -0.25, P < 0.001, respectively).

Our results provide further evidence that measurement of total 25D for assessment of vitamin D status in patients of African descent deserves reevaluation and suggest that alternative measures such as VMR should be considered.

© 2015 American Association for Clinical Chemistry.

PMID: 25922442
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Berg website

http://www.sph.umn.edu/lutsey-finds-flaw-in-vitamin-d-test-debunks-previous-study/ Fall 2015?

  • "The issue is binding proteins come in different genetic variations, and the test Powe used doesn’t measure well for a type of protein that is common in blacks. The test’s poor sensitivity to this type of protein led to the erroneously low results."

Attached files

ID Name Comment Uploaded Size Downloads
5791 2015-Berg-ClinicalChemistry-61-877.pdf admin 13 Aug, 2015 1.97 Mb 1322
5790 Bio56.jpg admin 13 Aug, 2015 67.47 Kb 1169
5789 Bio55.jpg admin 13 Aug, 2015 58.08 Kb 1120
5788 Bio45.jpg admin 13 Aug, 2015 66.31 Kb 1040
5787 Bio35.jpg admin 13 Aug, 2015 32.83 Kb 1132
5786 Bio33.jpg admin 13 Aug, 2015 68.66 Kb 1150
5785 Bio31.jpg admin 13 Aug, 2015 56.95 Kb 1119
5784 Bio30.jpg admin 13 Aug, 2015 48.55 Kb 1067
5783 Bio29.jpg admin 13 Aug, 2015 38.22 Kb 1072
5782 Bio1.jpg admin 13 Aug, 2015 50.43 Kb 1307
5781 Total D, not just bioavailable.pdf admin 13 Aug, 2015 3.80 Mb 1643