Title

Effects of substituting milk for other sugar-containing beverages on nutrient adequacy, body composition and bone health in adolescent girls

Date of Completion

January 2005

Keywords

Biology, Animal Physiology|Health Sciences, Nutrition|Health Sciences, Public Health|Health Sciences, Human Development

Degree

Ph.D.

Abstract

Changing beverage consumption patterns characterized by declining milk intake and increasing soft-drink consumption has contributed to poor calcium intake with 90% of adolescent girls consuming less than the RDA for calcium. Inadequate calcium and low levels of activity, particularly weight-bearing exercise, during adolescent growth can compromise development of peak bone mass, risk of fracture later in life and may also contribute to accumulation of excess body fat. Therefore this study examined the independent and additive effects of two interventions (milk supplementation and resistance training) on nutrient adequacy, body composition, and bone health in adolescent girls. Sixty-six adolescent girls (13--17 y) were placed into one of four groups: Milk only 0, Resistance training only [RT, n = 15]; Milk + resistance training [MRT, n = 15]; or Control [CON, n = 16]. Girls in the milk groups were provided 3 servings of milk/d for 12 wk. Girls in the training groups performed a supervised, progressive resistance training program for 12 wk. Compliance to the training and milk supplementation was exceptional (>97%). Differences in nutrient intakes between groups generally reflected the nutrient composition of milk with greater intakes of protein and improved nutrient adequacy for several B vitamins, vitamin A, vitamin D, calcium, magnesium, phosphorus, potassium, and zinc. Mean calcium intake was 758 and 1581 mg/d, in the non-milk and milk groups, respectively, with 100% of girls in the milk groups consuming >RDA of 1300 mg/d. There were no effects of milk on body composition or muscle performance, but resistance training had a main effect on body mass, lean body mass, muscle strength, and muscle endurance. There was a main effect of milk and resistance training on several measures of BMD. Changes in whole body BMD in the M, RT, MRT, and CON were 0.45, 0.52, 1.32, and -0.19%, respectively (P<0.01). In summary, improving nutrient status with milk supplementation or resistance training were both equally effective at improving BMD in adolescent girls. The additive nature of milk and resistance training on BMD highlights the need to combine interventions that utilize different mechanisms to optimize bone health. ^