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The toenail was examined as a biological monitor of Mg, Zn, and Cu intake using an observational case control model. The One Source Cohort matched 63 individuals in Columbia Missouri who took the One Source multivitamin with 63 control individuals. The matching criteria were based on age, sex, ethnicity, smoking status, and body mass index. The multivitamin contained supra-nutritional levels of Se, Mg, Cu, and Zn. The toenail clippings were examined for these elements using instrumental neutron activation analysis (INAA). A statistical analysis did not indicate a significant difference for Mg, Cu, or Zn between the nails of One Source supplement users and control subjects ( p<0.76, 0.55, and 0.85, respectively). The trace nutrient Se was used as an internal control. Previous studies have consistently demonstrated that toenail Se is positively correlated with Se supplement use and the analysis did result in a significant correlation in the toenails of One Source users and control subjects ( p<1·10−4). This internal Se control suggests that the One Source Cohort is largely free from misclassification errors that could interfere with the biomonitor response for the supranutritional intake of Mg, Cu, and Zn. [ABSTRACT FROM AUTHOR]

Numerous studies have demonstrated that the human toenail is a reliable biomonitor for the intake of Se and other elements. The objective of this study was to evaluate the use of the toenail as a biomonitor for Mn. Toenail specimens from One Source™ multivitamin users and matched controls were selected. Se was measured using established NAA methods, then Mn was measured via a new procedure. The Se results confirmed the accurate classification of the cohort. However, the nail did not show significant, positive response to Mn supplementation. We hypothesize that the persistence of exogenous Mn confounded the results. [ABSTRACT FROM AUTHOR]