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Am J Clin Nutr. 2010 Mar;91(3):571-7. doi: 10.3945/ajcn.2009.28082. Epub 2010 Jan 13.

Daily intake of 4 to 7 microg dietary vitamin B-12 is associated with steady concentrations of vitamin B-12-related biomarkers in a healthy young population.

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Department of Clinical Biochemistry, AS Aarhus University Hospital, Aarhus, Denmark.



Studies have questioned whether the current Recommended Dietary Allowance (RDA) of 2.4 microg vitamin B-12/d is adequate.


We examined the association between dietary vitamin B-12 intake and biomarkers of vitamin B-12 status.


Dietary vitamin B-12 intake was estimated, and biomarkers of vitamin B-12 status were measured, in healthy men and women (n = 299; age range: 18-50 y) who were recruited from a Florida community. The National Cancer Institute Diet History Questionnaire was used. Plasma cobalamin, total transcobalamin, holo-transcobalamin, methylmalonic acid (MMA), total homocysteine (tHcy), and autoantibodies against intrinsic factor (IF) and Helicobacter pylori were analyzed in blood samples.


Antibodies to H. pylori were detected in 12% of subjects (35/299), and negative results for IF antibodies were obtained for all subjects. The intake of vitamin B-12 correlated significantly with cobalamin, holo-transcobalamin, MMA, and tHcy. Subjects were divided into quintiles on the basis of their dietary vitamin B-12 intake (range: 0.42-22.7 microg/d), and biomarkers of vitamin B-12 status were plotted against estimated dietary vitamin B-12 intake. All biomarkers appeared to level off at a daily dietary vitamin B-12 intake between 4.2 and 7.0 microg.


In persons with normal absorption, our data indicate that an intake of 4-7 microg vitamin B-12/d is associated with an adequate vitamin B-12 status, which suggests that the current RDA of 2.4 microg vitamin B-12/d might be inadequate for optimal biomarker status even in a healthy population between 18 and 50 y of age.

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