|Thacher, Tom -|
|Obadofin, Michael -|
|O'Brien, Kimberly -|
|Abrams, Steven -|
Submitted to: Journal of Clinical Endocrinology and Metabolism
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 18, 2009
Publication Date: September 5, 2009
Citation: Thacher, T.D., Obadofin, M.O., O'Brien, K.O., Abrams, S.A. 2009. The effect of vitamin D2 and vitamin D3 on intestinal calcium absorption in Nigerian children with rickets. Journal of Clinical Endocrinology and Metabolism. 94(9):3314-3321. Interpretive Summary: We were interested in seeing whether vitamin D would increase calcium absorption in children in Africa with rickets. We measured vitamin D levels and gave supplemental vitamin D to 17 children with rickets. We then used non-radioactive calcium isotopes to measure how much of the mineral was absorbed into the body. We found that there was no change in calcium absorption with the extra vitamin D. These results demonstrate that rickets in these children was not related to vitamin D deficiency primarily, and adding additional vitamin D did not provide more calcium for the body.
Technical Abstract: Children with calcium-deficiency rickets have high 1,25-dihydroxyvitamin D values. The objective of the study was to determine whether vitamin D increased calcium absorption. This was an experimental study. The study was conducted at a teaching hospital. Participants included 17 children with nutritional rickets. The participants were randomized to 1.25 mg oral vitamin D3 (n = 8) or vitamin D2 (n = 9). Fractional calcium absorption 3 da after vitamin D administration was measured. Mean baseline 25-hydroxyvitamin D concentrations were 20 ng/ml (range 5–31 ng/ml). The increase in 25-hydroxyvitamin D was equivalent after vitamin D3 (29 +/- 10 ng/ml) or vitamin D2 (29 +/- 17 ng/ml). Mean 1,25-dihydroxyvitamin D values increased from 143 +/- 76 pg/ml to 243 +/- 102 pg/ml (P = 0.001), and the increase in 1,25-dihydroxyvitamin D did not differ between vitamin D2 and vitamin D3 (107 +/- 110 and 91 +/- 102 ng/ml, respectively). The increment in 1,25-dihydroxyvitamin D was explained almost entirely by the baseline 25-hydroxyvitamin D concentration (r2 = 0.72; P < 0.001). Mean fractional calcium absorption did not differ before (52.6 +/- 21.4%) or after (53.2 +/- 23.5%) vitamin D, and effects of vitamin D2 and vitamin D3 on calcium absorption were not significantly different. Fractional calcium absorption was not closely related to concentrations of 25-hydroxyvitamin D (r = 0.01, P = 0.93) or 1,25-dihydroxyvitamin D (r = 0.21, P = 0.24). The effect of vitamin D on calcium absorption did not vary with baseline 25-hydroxyvitamin D values or with the absolute increase in 25-hydroxyvitamin D or 1,25-dihydroxyvitamin D values. Despite similar increases in 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D with vitamin D2 or vitamin D3, fractional calcium absorption did not increase, indicating that rickets in Nigerian children is not primarily due to vitamin D-deficient calcium malabsorption.