Smith LM, et al. - Via two randomized clinical trials of healthy Caucasian and African American women who had vitamin D deficiency, the researchers assessed serum 25 hydroxyvitamin D (T25D), free 25hydroxyvitamin D (F25D), and serum parathyroid hormone (PTH) and evaluated the impact of vitamin D to see if there were any differences by race or age. A lower value of serum F25D and T25D in younger African American women was observed. However, because dietary vitamin D was comparable in the groups (African American and Caucasian groups), reduced UV exposure and reduced skin production of vitamin D were ascertained as the possible cause of low serum 25OHD in African American women.