Authors' recommendations: The published literature on vitamin A is large and its extent is likely similar to that of most other nutrients for which reference values have been or have yet to be established. The lesson learned from this exercise, focused on vitamin A, suggests that evidence-based methods, including systematic reviews, are applicable to the development of nutrient reference values, with appropriate nutrient specific modifications. When the volume of literature is large, rational and well-defined eligibility criteria must be applied in conducting a systematic review to manage the workload. Appropriate questions must be formulated so that the answers to those questions can be used to inform the derivation of a set of reference values and help to ensure transparency and reproducibility, and form the foundation for future updates as new data emerge.In the past, the process to derive a set of reference values for a particular nutrient has been, to a large degree, dependent on the make up of the expert panel. Using this new approach, it would be not only important that the members of the expert panel represent a balanced range of scientific views but that they also are familiarized with the process of conducting a systematic review and interpreting its results.It became apparent from this exercise that it would be desirable if nutrient reference values could be linked to specific health outcome(s). Although this issue presents challenges it should be considered in the future. The process in selecting specific health outcomes and intermediate outcomes (e.g., biomarkers, indicators) when specific health outcomes are not available for deriving of a reference value should be defined prior to starting systematic reviews.Some of the issues in the existing literature that will need to be addressed directly when applying systematic reviews to the process of establishing nutrient reference values include: generalizability of well-controlled experiments but with few subjects (e.g., <10) or subjects selected from limited spectrum of the general population; applicability of findings of animal studies to humans; generalizability of early studies that employed methodologies that are not state of the art or directly comparable to contemporaneous data; and appropriate interpretation and integration of scientific evidence from observational studies. Contemporary issues such as the role of genomics, and en masse nutrient fortification will also need to be factored in when undertaking this process.

Project Status: Completed

URL for project: http://www.ahrq.gov/downloads/pub/evidence/pdf/nutrition/nutrtp2.pdf

Year Published: 2009

URL for published report: http://www.ahrq.gov/clinic/tp/nutritn2tp.htm

English language abstract: An English language summary is available

Publication Type: Not Assigned

Country: United States

Organisation Name: Agency for Healthcare Research and Quality

Contact Address: Center for Outcomes and Evidence Technology Assessment Program, 540 Gaither Road, Rockville, MD 20850, USA. Tel: +1 301 427 1610; Fax: +1 301 427 1639;

Contact Name: martin.erlichman@ahrq.hhs.gov

Contact Email: martin.erlichman@ahrq.hhs.gov

Copyright: Agency for Healthcare Research and Quality (AHRQ)