Calcium Absorptive Effects of Vitamin D and Its Major Metabolites

R. P. Heaney
1997 Journal of Clinical Endocrinology and Metabolism  
The absorptive response to graded doses of vitamin D 3 , 25(OH)D, and 1,25(OH) 2 D was measured in healthy adult men after treatment periods of eight, four, and two weeks, respectively. While no relationship was found between baseline absorption and serum vitamin D metabolite levels, all three vitamin D compounds significantly elevated 45 Ca absorption from a 300 mg calcium load given as part of a standard test meal. 1,25(OH) 2 D was active even at the lowest dose (0.5 g/day), and the slope was
more » ... , and the slope was such that doubling of absorption would occur at an oral dose of approximately 3 g/day. 25(OH)D was also active in elevating absorption and did so without raising total 1,25(OH) 2 D levels. On the basis of the dose response curves for 1 equivalent to 1 000, 10 000, and 50 000 IU/day, and 0.065, 0.65, and 3.25 mmol/day, respectively. 2 equivalent to 0.025, 0.05, and 0.125 mmol/day. 3 equivalent to 1.2, 2.4, and 4.8 nmol/day.
doi:10.1210/jc.82.12.4111 pmid:9398723 fatcat:3ubnpsdrvrhnvmtw6tinct5olq