Stable metal isotopes: are we what we eat?

When nutrients move through the food chain, they fractionate their stable isotopes. Several years of research on Mg, Si, Ca, Fe, and Zn stable isotopes has shown that this is the case for all metabolic processes in both higher plants and animals. The most detailed picture has emerged from stable iron isotopes, and I will review how these isotopes reflect the human diet. The main result is that each human bears a distinct stable Fe isotope signature in its blood, that is set during intestinal absorption. But the human diet's Fe isotope composition is not uniform: vegetable an animal products are enriched in light Fe iotopes, whereas crop products reflect unfractionated Fe taken up from soil. These signatures are set by reduction, oxidation, and complexation in higher plants.