EFFECTS OF DAIRY-PRODUCTS ON BONE AND BODY-COMPOSITION IN PUBERTAL GIRLS

Objective: To study the effect of calcium supplementation with dairy p roducts on the bone and body composition of pubertal girls. Design: Ra ndomized control study with 12-month follow-up. Setting: General commu nity. 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 allowa nce of 1200 mg calcium daily. The other group ate their usual diet. Ma in outcome measures: Bone mineral content and density were measured at the radius, femoral neck, lumbar spine, and total body bone mineral b y single-photon and dual-energy x-ray absorptiometry at the start of t he 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 a t the same intervals. Serum calcium, phosphate, 25-hydroxyvitamin D, 1 ,25-dihydroxyvitamin D, alkaline phosphatase, magnesium, and albumin c oncentrations were determined at the start and end of the study. The u rinary calcium/creatinine ratio and hydroxyproline concentration were also determined. Results: The dairy group had higher intakes of calciu m, phosphate, vitamin D, and protein than control subjects. The dairy group had significantly greater increases during the 1-year study in b one 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, an d protein intakes were associated with the lumbar bone density and tot al body bone calcium. There were no differences in serum or urinary bi ochemical values between the two groups at the start or end of the stu dy. Conclusions: Young girls whose dietary calcium intake was provided primarily by dairy products at or above the recommended dietary allow ances had an increased rate of bone mineralization. Increased intake o f dairy foods did not increase overall total or saturated fat intake a nd was not associated with excessive weight gain or increased body fat .