Sufficient vitamin D reduces the risk of uterine fibroids, a report in the May issue of Epidemiology suggests. Some 1,036 premenopausal women (620 black, 416 white) ages 35 to 49 years were enrolled in the National Institute of Environmental Health Sciences Uterine Fibroid Study. Fibroid status was determined through ultrasonography. Vitamin D status was measured using radioimmunoassay of 25-hydroxyvitamin D in stored plasma samples and questionnaires on sun exposure. Only 26% of study participants had sufficient plasma levels of vitamin D. Women with sufficient vitamin D had an estimated 32% lower odds of having fibroids than those with insufficient levels. Sun exposure of more than one hour per day was also associated with a lower risk of fibroids. The association was essentially the same in blacks and whites.