Calcium supplementation and bone mineral density in adolescent girls.

OBJECTIVE

To evaluate the effect of calcium supplementation on bone acquisition in adolescent white girls.

DESIGN

A randomized, double-blind, placebo-controlled trial of the effect of 18 months of calcium supplementation on bone density and bone mass.

SUBJECTS

Ninety-four girls with a mean age of 11.9 + 0.5 years at study entry.

SETTING

University hospital in a small town.

INTERVENTIONS

Calcium supplementation, 500 mg/d calcium as calcium citrate malate; controls received placebo pills.

MAIN OUTCOME MEASURES

Bone mineral density and bone mineral content of the lumbar spine and total body were measured by dual-energy x-ray absorptiometry and calcium excretion from 24-hour urine specimens.

RESULTS

Calcium intake from dietary sources averaged 960 mg/d for the entire study group. The supplemented group received, on average, an additional 354 mg/d of calcium. The supplemented group compared with the placebo group had greater increases of lumbar spine bone density (18.7% vs 15.8%; P = .03), lumbar spine bone mineral content (39.4% vs 34.7%; P = .06), total body bone mineral density (9.6% vs 8.3%; P = .05), and 24-hour urinary calcium excretion (90.4 vs 72.9 mg/d; P = .02), respectively.

CONCLUSIONS

Increasing daily calcium intake from 80% of the recommended daily allowance to 110% via supplementation with calcium citrate malate resulted in significant increases in total body and spinal bone density in adolescent girls. The increase of 24 g of bone gain per year among the supplemented group translates to an additional 1.3% skeletal mass per year during adolescent growth, which may provide protection against future osteoporotic fracture.