13C Natural Abundance of Serum Retinol Is a Novel Biomarker for Evaluating Provitamin A Carotenoid-Biofortified Maize Consumption in Male Mongolian Gerbils uri icon


  • Background: Crops such as maize, sorghum, and millet are being biofortified with provitamin A carotenoids to ensure adequate vitamin A (VA) intakes. VA assessment can be challenging because serum retinol concentrations are homeostatically controlled and more sensitive techniques are resource-intensive.
  • Conclusions: Provitamin A efficacy and quantitative estimation of the relative contribution to dietary VA were demonstrated with the use of serum retinol delta C-13. This method could be used for maize efficacy or effectiveness studies and with other C-4 crops biofortified with provitamin A carotenoids (e.g., millet, sorghum). Advantages include no extrinsic tracer dose, 1 blood sample, and higher sensitivity than serum retinol concentrations alone.
  • Methods: The design was a 2 x 2 x 2 maize (orange compared with white) by carrot (orange compared with white) by a VA fortificant (VA+ compared with VA-) in weanling male Mongolian gerbils (n = 55), which included a 14-d VA depletion period and a 62-d treatment period (1 baseline and 8 treatment groups; n = 5-7/group). Liver VA and serum retinol were quantified, purified by HPLC, and analyzed by GC combustion isotope ratio mass spectrometry for C-13.
  • Objectives: We investigated changes in serum retinol relative differences of isotope amount ratios of C-13/C-12 (delta C-13) caused by natural C-13 fractionation in C-3 compared with C-4 plants as a biomarker to detect provitamin A efficacy from biofortified (orange) maize and high-carotene carrots.
  • Results: Treatments affected liver VA concentrations (0.048 +/- 0.039 to 0.79 +/- 0.24 mu mol/g; P < 0.0001) but not overall serum retinol concentrations (1.38 0.22 mu mol/L). Serum retinol and liver VA delta C-13 were significantly correlated (R-2 = 0.92; P < 0.0001). Serum retinol delta C-13 differentiated control groups that consumed white maize and white carrots (-27.1 +/- 1.2 delta C-13 parts per thousand) from treated groups that consumed orange maize and white carrots (-21.6 +/- 1.4 delta C-13 parts per thousand; P < 0.0001) and white maize and orange carrots (-30.6 +/- 0.7 delta C-13 parts per thousand; P < 0.0001). A prediction model demonstrated the relative contribution of orange maize to total dietary VA for groups that consumed VA from mixed sources.

publication date

  • 2016
  • 2016