title: Analyzing vitamin D in foods and supplements: methodologic challenges.
abstract: This report briefly reviews existing methods for analyzing the vitamin D content of fortified and unfortified foods. The existing chemical methods are similar; all are time consuming, require experienced technicians, and have only been validated for a few materials (eg, dairy products or animal feed materials). 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 analytic methods. Recently, the US Department of Agriculture, as part of a project to update the vitamin D values in the National Nutrient Database of Standard Reference, established an analytic methods committee to compare several existing vitamin D methods and to characterize 5 control materials (skim milk, processed cheese, cereal, orange juice, and salmon). Initial relative SDs for the 5 materials ranged from 35% to 50%. Elimination of systematic biases related to the methods and the standards yielded much more satisfactory relative SDs of 7% to 12%. This research has shown that existing methods for analyzing the 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 need certified reference materials for foods.
authors.affiliation: Food Composition and Methods Development Laboratory, Beltsville Human Nutrition Research Center, Agriculture Research Service, US Department of Agriculture, Beltsville, USA.
authors.forename: W Craig
authors.initials: WC
authors.lastname: Byrdwell
authors.forename: Jon
authors.initials: J
authors.lastname: Devries
authors.forename: Jacob
authors.initials: J
authors.lastname: Exler
authors.forename: James M
authors.initials: JM
authors.lastname: Harnly
authors.forename: Joanne M
authors.initials: JM
authors.lastname: Holden
authors.forename: Michael F
authors.initials: MF
authors.lastname: Holick
authors.forename: Bruce W
authors.initials: BW
authors.lastname: Hollis
authors.forename: Ronald L
authors.initials: RL
authors.lastname: Horst
authors.forename: Mark
authors.initials: M
authors.lastname: Lada
authors.forename: Linda E
authors.initials: LE
authors.lastname: Lemar
authors.forename: Kristine Y
authors.initials: KY
authors.lastname: Patterson
authors.forename: Katherine M
authors.initials: KM
authors.lastname: Philips
authors.forename: Maria T
authors.initials: MT
authors.lastname: Tarrago-Trani
authors.forename: Wayne R
authors.initials: WR
authors.lastname: Wolf
mesh_terms: D019411:Clinical Laboratory Techniques / Q000592:standards*; D005504:Food Analysis / Q000379:methods*; D005527:Food, Fortified / Q000032:analysis*; D006801:Humans; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014481:United States; D014807:Vitamin D / Q000031:analogs & derivatives / Q000032:analysis*
chemical_list: D014807:Vitamin D