Lactose does not enhance calcium bioavailability in lactose-tolerant, healthy adults

Abstract

Background: There is evidence from animal studies that lactose has a beneficial effect on intestinal calcium absorption. However, data concerning the effect of lactose on calcium absorption in lactose-tolerant adults are inconclusive. Objective: Our objective was to investigate the effect of lactose on calcium bioavailability in humans by the use of a stable-strontium test under controlled metabolic conditions. Design: Eleven healthy, lactose- tolerant subjects (8 women, 3 men) randomly received a bolus of 2.27 mmol strontium alone (load A), the bolus with 35 g lactose (load B), or the bolus with 17.5 g glucose and 17.5 g galactose (load C). Blood samples were drawn at 0, 15, 30, 60, 90, 180, 240, and 300 min. Urine specimens were collected during the time intervals -2 to 0, 0-2, 2-4, 4-6, and 6-24 h. Results: Pharmacokinetic parameters of strontium bioavailability were comparable for all 3 loads. In detail, fractional absorption at 240 min for loads A, B, and C was 12.1 ± 0.7%, 13.0 ± 1.1%, and 12.2 ± 0.7%, respectively. Areas under the curve for 0-240 min were 70.8 ± 6.3, 69.6 ± 3.5, and 65.8 ± 5.1 μmol·h/L for loads A, B, and C, respectively (NS). Moreover, fractional strontium excretion values of 5.1 ± 0.8% (load A), 5.8 ± 0.4% (load B), and 5.2 ± 0.8% (load C) were not significantly different. Conclusions: Lactose does not have a beneficial effect on calcium bioavailability in lactose- tolerant adults.