Analyzing vitamin D in foods and supplements: methodologic challenges.
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.
Byrdwell
W Craig
WC
Food Composition and Methods Development Laboratory, Beltsville Human Nutrition Research Center, Agriculture Research Service, US Department of Agriculture, Beltsville, USA.
Devries
Jon
J
Exler
Jacob
J
Harnly
James M
JM
Holden
Joanne M
JM
Holick
Michael F
MF
Hollis
Bruce W
BW
Horst
Ronald L
RL
Lada
Mark
M
Lemar
Linda E
LE
Patterson
Kristine Y
KY
Philips
Katherine M
KM
Tarrago-Trani
Maria T
MT
Wolf
Wayne R
WR
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*
D014807:Vitamin D