Effect of milk and lactose on zinc absorption in lactose-intolerant postmenopausal women.

We evaluated the effect of lactose intolerance on intestinal zinc absorption under various test conditions in a group of postmenopausal women. Fractional zinc absorption was studied with a dual-isotope technique using 65Zn and 51Cr (as nonabsorbable fecal markers). We performed four absorption tests on sixteen subjects with water (control), whole cow milk, lactose-free cow milk and lactose alone. Mean (+/- SEM) fractional zinc absorption was 0.558 +/- 0.032 with water, 0.276 +/- 0.031 with milk, 0.246 +/- 0.028 with lactose-free milk and 0.564 +/- 0.051 with lactose. No significant differences in zinc absorption were found under any of the test conditions between lactose-tolerant and lactose-intolerant subjects. Milk and lactose-free milk significantly reduced zinc absorption in both groups.