Vitamin D and Bone Health

Winter 2006 • Vol. 1 – No. 3 ABSTRACT Despite the availability of a wide variety of foods and supplements, and a growing interest in nutrition, the incidence of Vitamin D defi ciency is on the rise in the United States. Because vitamin D enhances the availability of calcium for bone mineralization, disorders marked by a loss of bone strength are likewise becoming more common. The causes of this trend are myriad—from inadequate supplementation, sun, and exercise, to excessive smog, clothing, and medications. Diet plays a relatively minor role in vitamin D defi ciency because of the limited number of foods that contain substantial amounts. Aging is more important because of the loss of hormonal activity that normally inhibits bone resorption. Although laboratory tests can detect vitamin D metabolite levels with great accuracy, we unfortunately don’t know what serum levels indicate vitamin D insuffi ciency, so we lack the earliest warning of the need for intervention to maintain bone health. Nonetheless, because our understanding of the mechanism of action of this vitamin has advanced over the years, the recommendations for an adequate intake of vitamin D have changed, along with recommendations for supplementation with calcium. Research must continue, however, to identify the earliest point along the continuum of serum vitamin D levels that justifi es therapeutic intervention.