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Abstract
This prospective study assessed plasma 25(OH)D concentrations in 4-8-year-old black and white prepubertal girls. The primary finding was that vitamin D status declined with age for both black and white females, although, after correcting for fat-free soft tissue, there were no longer declines in vitamin D status with age. Participants who acquired greater lean mass (represented by fat-free soft tissue) displayed greater decreases in plasma 25(OH)D levels. Black subjects had lower plasma 25(OH)D levels throughout the study, and the difference between white and black plasma 25(OH)D levels depended on the season of blood collection. Despite living in the southern United States, we observed vitamin D insufficiency (defined as having at least one plasma 25(OH)D measurement fall below 50 nmol/L) in 18% of the participants. When a cutoff value of 80 nmol/L was employed, 75% were insufficient. It is plausible that the increased use of vitamin D in muscle tissue with growth may contribute to a decline in circulating 25(OH)D.