Sherry A Tanumihardjo
University of Wisconsin, USA
Biography
Sherry A Tanumihardjo studies vitamin A and carotenoid metabolism, serves as Director of the Undergraduate Certificate in Global Health, and teaches at undergraduate and graduate levels including international field experiences. She is on the Executive Board for the UW Global Health Institute. She has more than 160 publications and chapters published. She has presented at more than 280 domestic and international venues. She has served as a reviewer for many journals and is the recipient of the following awards: Who’s Expert Advisory Panel, G Malcolm Trout Visiting Scholar at Michigan State University, Ruth Pike Lectureship at Pennsylvania State University, Alex Malaspina ILSI Future Leader, Dannon Creative Leadership Institute, Endowed Chair and Vilas Associate at UW
Abstract
Maize is a staple crop in many parts of the world and has been targeted for biofortification with provitamin A carotenoids to provide more vitamin A (VA) to consumers. VA assessment can be challenging because static serum retinol concentrations do not always reflect total body stores. Maize is a C4 plant, meaning that it is naturally enriched with 13C. For effectiveness studies with provitamin A carotenoids, changes in 13C natural enrichment of serum retinol can be determined as a measure of biofortified (orange) maize consumption. To show proof-of-concept, a study in Mongolian gerbils (n=55) investigated changes in the 13C/12C (δ13C) of serum retinol from feeding orange maize (C4) and carrots (C3) for 62 d. The design was a 2x2x2 maize (orange vs. white) by carrot (orange vs. white) by VA fortificant (VA+ vs. VA-). Liver and serum VA δ13C was analyzed by gas chromatography-combustionisotope ratio mass spectrometry. Serum and liver VA δ13C were significantly correlated (R2=0.92, P<0.0001). Serum retinol δ13C differentiated controls consuming white maize and white carrots (-27.1±1.2 δ13C‰) from groups consuming orange maize and white carrots (-21.6±1.4 δ13C‰, P<0.0001) and white maize and orange carrots (-30.6±0.7 δ13C‰, P<0.0001). Natural abundance measurements were applied to an efficacy study in Zambian children, in which orange or white maize was fed for 90 days. In these children, 13C natural abundance was higher
after two months in the orange maize group compared with the white maize group (P<0.05). Predictions made from equations developed in the gerbil study estimate that maize provided 11% (2-21%, 95% CI) of recent dietary VA in this group. Shifts in serum retinol δ13C can be used for maize and other biofortified C4 crop effectiveness studies. Advantages of this method in effectiveness trials include no extrinsic tracers, one blood sample, and high sensitivity compared with measuring serum retinol alone.
