We propose a 6 month randomized placebo controlled trial of vitamin D (vitamin D3 1000 IU/day vs. placebo) initiated during October through March (during fall and winter) in 8 to 14 year old African American and Caucasian children. The results of the trial will help establish the cutoff threshold value of serum 25(OH)D for defining vitamin D insufficiency in preadolescent and adolescent children. Safety of vitamin D supplementation will be assessed by measuring serum calcium at 0, 2 and 6 months and by monitoring for adverse events. Currently recommended adequate intake for vitamin D of 200 IU daily may not meet the body's daily needs for vitamin D. Therefore, it is likely that a higher level of daily vitamin D intake may be needed to meet the body's skeletal and non-skeletal demands for vitamin D. Determining the dietary required intake of vitamin D for the prevention of vitamin D insufficiency during childhood has immense public health potential for addressing health disparities and ensuring better bone health during adulthood. The primary outcome measure will be serum 25(OH)D and parathyroid hormone (PTH). The secondary outcome measures will include: markers of bone formation (serum P1NP) and bone resorption (serum CTX).We will also examine differences in serum 25(OH)D, PTH, and markers of bone turnover in African American vs. Caucasian children.