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J Clin Endocrinol Metab. 2014 Sep;99(9):3373-81. doi: 10.1210/jc.2014-1714. Epub 2014 Jun 2.

25(OH)D2 half-life is shorter than 25(OH)D3 half-life and is influenced by DBP concentration and genotype.

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Medical Research Council Human Nutrition Research (K.S.J., S.A., D.H., A.P., I.S.), Cambridge CB1 9NL, United Kingdom; Medical Research Council Keneba (K.S.J., A.P.), The Gambia; Clinic and Laboratory of Experimental Medicine and Endocrinology (R.B.) and Laboratory for Translational Genetics (D.L.), Katholieke Universiteit, B-3000 Leuven, Belgium; and Vesalius Research Center (D.L.), VIB, Katholieke Universiteit, B-3000, Leuven, Belgium.



There is uncertainty over the equivalence of vitamins D2 and D3 to maintain plasma 25-hydroxyvitamin D (25(OH)D).


The objective of the study was to compare the plasma half-lives of 25(OH)D2 and 25(OH)D3 in two distinct populations with different dietary calcium intake and 25(OH)D status.


Healthy men (aged 24 and 39 y), resident in The Gambia (n = 18) or the United Kingdom (n = 18) participated in the study.


The intervention included an oral tracer dose of deuterated-25(OH)D2 and deuterated-25(OH)D3 (both 40 nmol). Blood samples were collected over 33 days.


25(OH)D2 and 25(OH)D3 plasma half-lives, concentrations of 25(OH)D, and vitamin D binding protein (DBP) and DBP genotypes were measured.


25(OH)D2 half-life [mean (SD)] [13.9 (2.6) d] was shorter than 25(OH)D3 half-life [15.1 (3.1) d; P = .001] for countries combined, and in Gambians [12.8 (2.3) d vs 14.7 (3.5) d; P < .001], but not in the United Kingdom [15.1 (2.4) d vs 15.6 (2.5) d; P = .3]. 25(OH)D concentration was 69 (13) and 29 (11) nmol/L (P < .0001), and the DBP concentration was 259 (33) and 269 (23) mg/L (P = .4) in The Gambia and United Kingdom, respectively. Half-lives were positively associated with plasma DBP concentration for countries combined [25(OH)D2 half-life: regression coefficient (SE) 0.03 (0.01) d per 1 mg/L DBP, P = .03; 25(OH)D3 half-life: 0.04 (0.02) d, P = .02] and in Gambians [25(OH)D2 half-life: 0.04 (0.01) d; P = .02; 25(OH)D3 half-life: 0.06 (0.02) d, P = .01] but not in UK participants. The DBP concentration × country interactions were not significant. DBP Gc1f/1f homozygotes had shorter 25(OH)D2 half-lives compared with other combined genotypes (P = .007) after correction for country.


25(OH)D2 half-life was shorter than 25(OH)D3 half-life, and half-lives were affected by DBP concentration and genotype. The stable isotope 25(OH)D half-life measurements provide a novel tool to investigate vitamin D metabolism and vitamin D expenditure and aid in the assessment of vitamin D requirements.

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