An inulin-type fructan enhances calcium absorption in young adults throughout the GI tract with the largest effect occurring in the colon.

Background: Calcium absorption efficiency and bone mineral mass are increased in adolescents who receive inulin-type fructans (ITF). The mechanism of action is unknown but in animal models appears to be related to increased colonic calcium absorption. Methods: We conducted a calcium kinetic study in young adults after dosing 42Ca orally and also giving 46Ca IV. Kinetic measurements were performed before and after 6 weeks of supplementation with 8 g/d of a mixed short and long degree of polymerization (DP) ITF. Blood samples were collected over 26 hours and a 48-hour urine collection obtained. The area under the curve of the oral tracer in the blood was calculated and relative increased absorption throughout the sampling period determined. Results: Eight young adults (of 13 studied), with average calcium intake about 900 mg/d responded to the ITF with an increased calcium absorption of at least 3%. The average increase in absorption was 8.3% (72 mg/d). Colonic absorption, defined as absorption that occurred more than 7 hours after oral dosing, represented 60-67% of the increase, or about 45 mg/d calcium absorption in the colon. Discussion: These findings suggest that multiple mechanisms account for the increased calcium absorption associated with the ingestion of a mixed long and short DP ITF. These likely include increased solubility and increased absorptive surface area throughout the intestine. [ABSTRACT FROM AUTHOR]