Vitamin D research and public health nutrition: a current perspective.

This 2017 special issue of Public Health Nutrition features nineteen research manuscripts all relevant to the role of vitamin D nutritional status in the risk and prevention of chronic diseases of public health importance. A useful barometer gauging the worldwide growing interest in vitamin D and health research is shown by over 13 000 studies abstracted in PubMed over the last 5 years alone, all with a focus on vitamin D. Vitamin D deficiency in Europe is associated with adverse health outcomes whose direct and indirect medical cost burdens have been estimated in the hundreds of billions of Euros, which underlines the importance of this work to public health. Dedicating a special issue to these recently accepted vitamin D studies provides Public Health Nutrition editors with an opportunity to set in perspective the diverse aspects of the continued growing interest in vitamin D nutritional status, its health importance, and the impact of the many recent innovations in analytical methods, assay standardization programmes and the underlying factors contributing to the controversy over serum cut-off values defining vitamin D nutritional status. Newer standardized analytical methods now enable research exploring the many gaps in our understanding of vitamin D nutritional status which many of these papers address, as well as the association with reduced risk of disease and other beneficial health effects. The common feature among all the papers in this special vitamin D issue is the measurement of vitamin D status or the circulating concentrations of 25-hydroxyvitamin D (25 (OH)D, nmol/l or ng/ml). There is a growing demand to assess vitamin D status in order to screen for deficiency, monitor efficacy of supplementation or fortification, or assess the association between vitamin D status and chronic diseases including osteoporosis, diabetes, cancer, CVD, infection and autoimmune or neurological disorders. To meet this demand, less labour-intense assay methods have been developed along with certified external standards and proposed criteria for defining vitamin D deficiency/sufficiency. The goal of this perspective is to inform researchers about the currently accepted assay methods and quality control procedures used to determine 25(OH)D concentrations and the most widely accepted criteria for establishing vitamin D status. We present some background information describing relevant new evidence in four areas defining important public health gaps in knowledge that are addressed by many of the studies in this issue. Our intent is to provide insight into how these studies contribute to these gaps in our understanding of vitamin D status and, more importantly, how the study findings may impact public health nutrition policy and practices.