Scanning for new evidence to prioritize updates to the Dietary Reference Intakes: case studies for thiamin and phosphorus

Background: Dietary Reference Intakes (DRIs) are fundamental to inform national nutrition policy. However, a regular systematic review of the 51 nutrients that have DRIs has limited feasibility, and many DRIs have not been reviewed in >15 y. Objective: To address this issue, individuals (nutrient review group) who were members of the Food and Nutrition Board developed a streamlined, evidence-based methodology that could be used to identify nutrients potentially in need of a systematic review. Design: The proposed methodology, termed an evidence scan, comprises several steps. First, an analytic framework is developed to identify markers of associations between intake of a nutrient and a corresponding clinical outcome. Next, the framework is used to direct the identification of keywords for a scan of published research that is potentially relevant to intake requirements or upper intake levels for a nutrient. Last, a panel of content experts selects the abstracts that are likely to be relevant and reviews the full publications. The results may be used to determine whether a revision of the nutrient's DRI is an immediate priority but would not supplant a comprehensive systematic evidence review. Results: To illustrate the process, 2 nutrients were selected as case studies: thiamin and phosphorus (DRIs were last set in 1998 and 1997, respectively). Using the evidence scan for thiamin, we identified 70 potentially relevant abstracts, of which 9 full publications were reviewed. For phosphorus, 127 potentially relevant abstracts were identified, and 29 full publications were reviewed. Conclusions: From the review of these 2 nutrients, the nutrient review group concluded that there was insufficient new evidence to assign a high priority to a comprehensive systematic review for either thiamin or phosphorus. Evidence scanning is an efficient method of identifying DRI nutrients that are most in need of either a new or an updated systematic review.