While a large percentage of children have low blood vitamin D levels, the significance of these low levels and the impact on health is unclear. The purpose of this project is to determine the effects of varying doses of vitamin D supplementation over 12 weeks on blood indicators of health in white and black children, aged 9 to 13 years, from both the northern and southern US.

Vitamin D intakes in children do not meet current US Dietary Reference Intake recommendations and emerging evidence suggests that a significant number of children, particularly those with darker skin pigmentation, have inadequate levels of serum 25-hydroxyvitamin D [25(OH)D]. The optimum level of circulating 25(OH)D has not been clearly defined in children, nor is it known what functional outcome measures are ideal for defining this level, or if these requirements would differ by race. Graded doses of vitamin D3 supplementation will be used in this dual-site, 12-week trial. The investigators hypothesize that a dose-response relationship will be observed between vitamin D supplementation and intermediate endpoints of skeletal health, and that race will modify these responses.

Inclusion Criteria:

• Healthy
• Non-Hispanic
• Male, 10-13 years of age or female 9-11 years of age
• Within genitalia or breast stage 2/3
• Willing to provide blood/urine samples
• Free from taking vitamin, mineral or herbal supplements
• Able to swallow tablets

Exclusion Criteria:

• Menarche (females)
• Known bone diseases or disease known to influence bone metabolism (e.g. cerebral palsy, intestinal malabsorption, juvenile rheumatoid arthritis)
• Known growth disorder
• The use of medications that influence bone metabolism (e.g. corticosteroids, Attention Deficit Hyperactivity Disorder (ADHD) medications).