An inulin-type fructan enhances calcium absorption primarily via an effect on colonic absorption in humans
J Nutr.2007 Oct;137(10):2208-12.
Abrams SA, Hawthorne KM, Aliu O, Hicks PD, Chen Z, Griffin IJ.
Calciumabsorption efficiency and bone mineral mass are increased in adolescents who regularly consume inulin-typefructans (ITF). The mechanism of action in increasing absorption is unknown but may be related to increased coloniccalciumabsorption. We conducted a study in young adults designed to evaluate these mechanisms with a kinetic technique using (42)Ca orally and (46)Ca dosed i.v. Those who responded to 8 wk of supplementation with 8 g of a mixed short and long degree of polymerization ITF by increasing their calciumabsorption had kinetic measurements analyzed to evaluate the time course of absorption. The area under the curve of the oral tracer in the blood during the 26 h after dosing was calculated and the time dependence of increased absorption determined. Eight young adults (of 13 studied), with mean calcium intake approximately 900 mg/d, responded to the ITF with an increased calciumabsorption of at least 3%. In responders, absorption increased from 22.7 +/- 11.3% to 31.0 +/- 15.3%. Colonicabsorption, defined as absorption that occurred >7 h after oral dosing, represented 69.6 +/- 18.6% of the increase, or 49 +/- 28 mg/d. These findings suggest that, in those who respond to ITF, its effects on calciumabsorption occur principally in the colon. This benefit to ITF may be especially important when absorption in the small intestine is impaired for anatomic or physiological reasons.