Abstract
Summary
Total serum vit. B12 concentrations were determined in 528 individuals by the L. leichmannii method, and a justification for the choice of this method of assay is presented. The individuals studied were “normal” as far as physical health is concerned, and the major variable was age. In such persons there is a trend toward lower serum concentration of vit. B12 in the aged than in younger age groups. Although this difference is statistically significant, the biological importance of this finding is not apparent. There is wide individual difference of values in serum vit. B12 concentration at all age levels, but in this “normal” group values below 200 μμg/ml and above 1000 μμg/ml were uncommon. The average for the entire 528 individuals was 560 μμg/ml, the 95% confidence bands being 70 and 1060 μμg/ml respectively.
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