Effect of dietary calcium on bone density in growing rabbits

Abstract

Reductions in peak bone mass at skeletal maturity may increase the risk for the subsequent development of osteoporosis. Although changes in calcium intake can modify the rate of decline in bone density in the mature skeleton, longitudinal assessments of the effect of dietary calcium supplementation during skeletal growth on peak bone mass have not been done in humans or experimental animals. Thus quantitative computed tomography (QCT) was used to monitor changes in vertebral bone density at 6-wk intervals during growth from 8 wk of age until skeletal maturity at 35 wk in male New Zealand White rabbits maintained on diets containing 0.15% (low Ca), 0.45% (normal Ca), or 1.35% (high Ca) calcium. Serum parathyroid hormone (PTH) and calcitriol levels increased, and renal calcium excretion decreased in low Ca compared with normal Ca; in contrast, serum calcitriol levels decreased and renal calcium excretion increased from control values in high Ca. Vertebral bone density by QCT did not differ during growth between high Ca and normal Ca, and peak values at epiphyseal closure also did not differ in these two groups. Vertebral bone density was lower, however, throughout the study in low Ca, and peak values at epiphyseal closure remained below those in either normal Ca or high Ca. Quantitative bone histology revealed decreases in cortical thickness in the third lumbar vertebra in low Ca, whereas trabecular bone area did not differ among groups; there was no histological evidence of osteomalacia in low Ca. Thus dietary calcium restriction during growth reduces peak bone mass at skeletal maturity, but raising dietary calcium intake above normal levels does not increase peak bone mass in this experimental model.

Calcium-enriched foods and bone mass growth in prepubertal girls: a randomized, double-blind, placebo-controlled trial.

“…Similarly, in a study undertaken in prepubertal Chinese girls, calcium supplements were associated with a higher radial BMD gain (30). Taken together, these results (as well as other studies in experimental animals [36] and human subjects [37,38]) suggest that the appendicular skeleton, (particularly regions predominantly composed of compact bone) appear to be more sensitive than the axial skeleton to the effect of calcium supplementation above RDA. Importantly, however, calcium supplementation appears also to have an effect on BMC and bone size at the level of the lumbar spine.…”

Rabbit dental disease and calcium metabolism – the science behind divided opinions

“…In those rabbits fed a high‐calcium diet serum calcitriol concentrations decreased and renal calcium excretion increased (Gilsanz et al . ).…”

Changes in bone mineral density in survivors of childhood acute lymphoblastic leukemia

“…Cure rates for children with ALL now approach 80% 1, and survivors of childhood ALL remain at risk of low BMD long after they have completed therapy 5–16. Factors that contribute to deficient BMD in ALL survivors include the disease process itself, chemotherapy 5–23, irradiation of endocrine organs that control bone accretion 5,24–33, poor nutrition 16,34–38, genetic predisposition 9,38–44, inactivity 35,45–48, and pubertal status 49–52. After completion of therapy, these bone mineral deficits may predispose survivors to osteoporosis of greater severity and earlier onset.…”