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New Method Developed for Measuring Vitamin B12
By Rosalie Marion Bliss
September 16, 2003
A new method to measure quantities of vitamin B12, both in foods and in dietary supplements, has been developed by Agricultural Research Service scientists.
Vitamin B12 is an essential nutrient linked to human growth and cell development. The Food and Nutrition Board of the Institute of Medicine, which establishes reference values for nutrient intakes, advocates research related to absorption and bioavailability of this important nutrient.
Scientifically, vitamin B12 is a family of compounds called cobalamins. Each form has its own potential biological activity in terms of absorption and potency. Naturally occurring forms of B12 are found predominantly in meat and dairy products. A synthetic form, called cyanocobalamin, is used in the United States to fortify foods and to make dietary supplements.
A microbiological assay has commonly been used to analyze the amount of B12 in samples, but that method takes days and is expensive. Another drawback is that it measures the total amount of B12 in a sample, but not how much of each of the individual forms.
The newer method for quantifying cobalamins uses one of two separation techniques (one is capillary electrophoresis, or CE, and the other is micro-high-performance liquid chromatography, or HPLC) combined with a detection technique called inductively coupled plasma mass spectrometry, or ICP-MS.
This hybrid method allows scientists to quickly detect and measure levels of specific cobalamins, according to research chemist Nancy Miller-Ihli, who heads the trace element lab in the Food Composition Laboratory at the ARS Beltsville Human Nutrition Research Center in Beltsville, Md. ARS is the U.S. Department of Agriculture's chief scientific research agency.
The ARS lab is now testing various food and supplement samples using CE-ICP-MS to measure the various cobalamins. Preliminary results report important data findings in commercial vitamin supplements. Future projects will focus on human breast milk.
Accuracy in measuring the quantity of each of the cobalamins in foods and supplements is crucial for understanding absorption mechanisms, which will lead to health recommendations important to the public.