Determination of Optimum Vitamin D Nutrition in Young Women

The main objective of this proposal was to study the effect of increasing doses of vitamin D3 in a group of young Caucasian and African American women with vitamin D insufficiency, that is with a serum 25OHD 20 ngml and an adequate calcium intake of 1200 -1400mgday. African American women generally have lower levels 25-vitamin D. This was a double blind randomized placebo controlled study. There were 5 treatment arms, four vitamins D3 dose groups - 400, 800, 1600, 2400 IUday and a placebo. Calcium citrate tablets were given to maintain the calcium intake between 1200-1400mgd. The study plan was to recruit up to 100 Caucasian and 100 African America women subjects between ages 25 to 45 years. The primary outcomes were the changes in serum 25-hydroxyvitamin D and serum Parathyroid hormone. Secondary outcomes were calcium absorption and for safety measurements of serum calcium and 24 hour urine calcium. 198 women 119 Caucasian, 78 African Americanwere randomized and 128 completed the study one year later. The final results show the response to oral vitamin D is the same in both Caucasian and African American young women. The implication is that vitamin D metabolism is the same and that lower vitamins D levels in African Americans are due to increased skin melanin filtering out the ultraviolet light. This is the first study to estimate the Recommended Dietary Allowance RDA in young people and shows that the RDA for vitamin D is 400-800 IU daily.