Intestinal calcium absorption in patients after jejuno-ileal bypass or small intestinal resection and the effect of vitamin D.

A forearm counter and double-isotope technique were used to measure intestinal calcium absorption in 21 patients after jejuno-ileal bypass for obesity or small intestinal resection. In all but 2 patients calcium absorption was below the normal range for 10 male controls. 3 weeks treatment with 1-alpha-hydroxyvitamin D, 1 microgram b.d., or 1,25-dihydroxyvitamin D, 1 microgram b.d., was associated with significant increases in absorption whereas 3 weeks treatment with 24,25-dihydroxyvitamin D had no effect. This study demonstrates that oral 1,25-dihydroxyvitamin D or 1-alpha-hydroxyvitamin D are effective in increasing calcium absorption.