Title: Analyzing vitamin D in foods and supplements: methodological challenges Authors
|Byrdwell, W Craig|
|Devries, Jon - MEDALLION LABS|
|Holick, Michael - BOSTON UN MED CNTR|
|Hollis, Bruce - MED UN SOUTH CAROLINA|
|Horst, Ronald - HEARTLAND ASSAYS|
|Lada, Mark - COCA-COLA CO|
|Phillips, Katherine - VPI|
|Tarrago-Trani, Maria - VPI|
Submitted to: American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 21, 2008
Publication Date: August 1, 2008
Citation: Byrdwell, W.C., Devries, J., Exler, J., Harnly, J.M., Holden, J.M., Holick, M., Hollis, B., Horst, R., Lada, M., Lemar, L.E., Patterson, K.K., Phillips, K., Tarrago-Trani, M., Wolf, W.R. 2008. Analyzing vitamin D in foods and supplements: Methodological challenges. American Journal of Clinical Nutrition. 88:554S-557S. Interpretive Summary: This report summarizes the analytical work over the past year to characterize the existing methods for vitamin D and to establish and develop control materials that will allow analytical labs to evaluate the accuracy of their results. The first part of the paper is a brief review of existing validated methods for analyzing the vitamin D content of fortified and non-fortified foods and available reference standards from metrological institutions. Existing methods can be summarized as tedious, time consuming, and demanding of an extreme attention to detail. Existing standards are generally unavailable and unsuited to the expanding list of foods now fortified with vitamin D. The second part of the paper describes the efforts of the Analytical Methods Committee (organized by USDA) to reach a consensus on the concentration of vitamin D in 5 control materials (skim milk, processed cheese, cereal, orange juice, and salmon). The Committee concludes that although existing methods are very difficult and time-consuming they can provide accurate results. The Committee also stressed the need for new food reference materials and simpler, more robust analytical methods for vitamin D.
Technical Abstract: This report briefly reviews existing methods for analyzing the vitamin D content of fortified and non-fortified foods. The existing chemical methods are similar; all are time consuming; require experienced technicians; have only been validated for dairy products or animal feed materials; and have only been validated for vitamin D3, not vitamin D2. This report also describes the lack of standard reference materials with certified values for vitamin D that laboratories need to guarantee the accuracy of existing analytical methods. Recently, the U.S. Department of Agriculture, as part of a project to update the vitamin D values in the National Nutrient Database of Standard Reference, established an analytical methods committee to compare several existing vitamin D methods and to characterize five control materials (skim milk, processed cheese, cereal, orange juice, and salmon). Initial relative standard deviations (RSDs) for the five materials ranged from 35% to 50%. Elimination of systematic biases related to the methods and the standards yielded much more satisfactory RSDs of 7% to 12%. This research demonstrated that existing methods for analyzing vitamin D content in foods can produce accurate results. A new, simpler, and faster method, however, would greatly benefit the field. To guarantee accuracy, we desperately need certified reference materials for foods.