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


METHODS
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 micromol*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.
Zittermann
A
A
Department of Nutrition Science, University of Bonn, Germany. a.zittermann@uni-bonn.de
Bock
P
P
Drummer
C
C
Scheld
K
K
Heer
M
M
Stehle
P
P
D000328:Adult; D001682:Biological Availability; D001786:Blood Glucose / Q000378:metabolism; D002136:Calcium, Dietary / Q000008:administration & dosage / Q000493:pharmacokinetics*; D018592:Cross-Over Studies; D005260:Female; D005690:Galactose / Q000008:administration & dosage; D005947:Glucose / Q000008:administration & dosage; D006801:Humans; D007408:Intestinal Absorption / Q000187:drug effects; D007700:Kinetics; D007785:Lactose / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D016226:Phosphorus, Dietary / Q000008:administration & dosage; D010919:Placebos; D013324:Strontium / Q000097:blood / Q000493:pharmacokinetics / Q000652:urine
D001786:Blood Glucose; D002136:Calcium, Dietary; D016226:Phosphorus, Dietary; D010919:Placebos; D005947:Glucose; D007785:Lactose; D005690:Galactose; D013324:Strontium