- Plasma hepcidin is a modest predictor of dietary iron bioavailability in humans, whereas oral iron loading, measured by stable-isotope appearance curves, increases plasma hepcidin. Zimmermann, M.B., Troesch, B., Biebinger, R., Egli, I., Zeder, C., Hurrell, R.F. Am. J. Clin. Nutr. (2009)