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Division of Radiobiology, School of Medicine, University of Utah, Salt Lake City, UT 84112
Lactose promotes the intestinal absorption of calcium independent of the vitamin D endocrine system. The purpose of this study was to determine the effect of lactose supplementation on endochondral bone growth, bone development and mineralization in weanling rats fed a vitamin Ddeficient diet. Rat pups were weaned from vitamin Ddeficient dams and fed a vitamin Ddeficient diet containing sucrose as the primary carbohydrate source or a similar diet but containing 20% lactose. After 4 wk, body weights, serum calcium levels and endochondral bone elongation rates in the lactose-fed animals were higher than in rats fed the sucrose diet. In addition, bone weights, bone calcium content, percent bone ash of bone dry weight, percent metaphyseal osseous tissues and bone osteoid content in the lactose-fed rats were different from those in the rats fed the sucrose diet. In all cases the changes in osseous tissues that were observed in the animals fed the lactose-supplemented diet were toward normal values as observed in age-matched animals fed a vitamin Dreplete diet. The improvements in bone growth and development due to lactose supplementation occurred independent of the vitamin D endocrine system and are likely the result of improved calcium absorption in the intestine.
KEY WORDS: lactose calcium vitamin D bone
1 Supported by a grant from the National Dairy Board administered in cooperation with the National Dairy Council, Public Health Service Grant No. DE-06007 from the National Institutes of Health and U.S. Department of Energy Contract No. DEAC0276EV00119.
Manuscript received 8 December 1986. Revision accepted 10 September 1987.