Effects of dairy products on bone and body composition in pubertal girls.

OBJECTIVE

To study the effect of calcium supplementation with dairy products on the bone and body composition of pubertal girls.

DESIGN

Randomized control study with 12-month follow-up.

SETTING

General community.

SUBJECTS

Forty-eight white girls whose mean age was 11 years and sexual development at Tanner stage 2.

INTERVENTION

One group's diet was supplemented with dairy products to the recommended dietary allowance of 1200 mg calcium daily. The other group ate their usual diet.

MAIN OUTCOME MEASURES

Bone mineral content and density were measured at the radius, femoral neck, lumbar spine, and total body bone mineral by single-photon and dual-energy x-ray absorptiometry at the start of the study and after 3, 6, 9, and 12 months. Body composition (lean body mass and body fat) was measured by dual-energy x-ray absorptiometry at the same intervals. Serum calcium, phosphate, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, alkaline phosphatase, magnesium, and albumin concentrations were determined at the start and end of the study. The urinary calcium/creatinine ratio and hydroxyproline concentration were also determined.

RESULTS

The dairy group had higher intakes of calcium, phosphate, vitamin D, and protein than control subjects. The dairy group had significantly greater increases during the 1-year study in bone mineral density at the lumbar spine bones (22.8% +/- 6.9% vs 12.9% +/- 8.3%) and in total body bone mineral (14.2% +/- 7.0% vs 7.6% +/- 6.0%) than control subjects. Dietary calcium, phosphate, vitamin D, and protein intakes were associated with the lumbar bone density and total body bone calcium. There were no differences in serum or urinary biochemical values between the two groups at the start or end of the study.

CONCLUSIONS

Young girls whose dietary calcium intake was provided primarily by dairy products at or above the recommended dietary allowances had an increased rate of bone mineralization. Increased intake of dairy foods did not increase overall total or saturated fat intake and was not associated with excessive weight gain or increased body fat.