The effect of vitamin D2 and vitamin D3 on intestinal calcium absorption in Nigerian children with rickets.
BACKGROUND
Children with calcium-deficiency rickets have high 1,25-dihydroxyvitamin D values.


OBJECTIVE
The objective of the study was to determine whether vitamin D increased calcium absorption.


METHODS
This was an experimental study.


METHODS
The study was conducted at a teaching hospital.


METHODS
Participants included 17 children with nutritional rickets.


METHODS
The participants were randomized to 1.25 mg oral vitamin D(3) (n = 8) or vitamin D(2) (n = 9).


METHODS
Fractional calcium absorption 3 da after vitamin D administration was measured.


RESULTS
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 D(3) (29 +/- 10 ng/ml) or vitamin D(2) (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 D(2) and vitamin D(3) (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 (r(2) = 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 D(2) and vitamin D(3) 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.


CONCLUSIONS
Despite similar increases in 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D with vitamin D(2) or vitamin D(3), fractional calcium absorption did not increase, indicating that rickets in Nigerian children is not primarily due to vitamin D-deficient calcium malabsorption.
Thacher
Tom D
TD
Department of Family Medicine, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905, USA. thacher.thomas@mayo.edu
Obadofin
Michael O
MO
O'Brien
Kimberly O
KO
Abrams
Steven A
SA
D002118:Calcium / Q000378:metabolism*; D002648:Child; D002675:Child, Preschool; D002762:Cholecalciferol / Q000494:pharmacology*; D004872:Ergocalciferols / Q000494:pharmacology*; D005260:Female; D006801:Humans; D007408:Intestinal Absorption; D008297:Male; D009549:Nigeria; D012279:Rickets / Q000378:metabolism*; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood
D004872:Ergocalciferols; D014807:Vitamin D; D002762:Cholecalciferol; C097949:1,25-dihydroxyvitamin D; C104450:25-hydroxyvitamin D; D002118:Calcium