title: Zn and Fe biofortification: the right chemical environment for human bioavailability.
abstract: A considerable fraction of global disease burden and child mortality is attributed to Fe and Zn deficiencies. Biofortification, i.e. the development of plants with more bioavailable Zn and Fe, is widely seen as the most sustainable solution, provided suitable crops can be generated. In a cereal-dominated diet availability of Fe and Zn for absorption by the human gut is generally low and influenced by a highly complex chemistry. This complexity has mostly been attributed to the inhibitory effect of Fe and Zn binding by phytate, the principal phosphorus storage compound in cereal and legume seeds. However, phytate is only part of the answer to the multifaceted bioavailability question, albeit an important one. Recent analyses addressing elemental distribution and micronutrient speciation in seeds strongly suggest the existence of different Fe and Zn pools. Exploration of natural variation in maize showed partial separation of phytate levels and Fe bioavailability. Observations made with transgenic plants engineered for biofortification lend further support to this view. From a series of studies the metal chelator nicotianamine is emerging as a key molecule. Importantly, nicotianamine levels have been found to not only increase the loading of Fe and Zn into grains. Bioavailability assays indicate a strong activity of nicotianamine also as an enhancer of intestinal Fe and Zn absorption.
authors.affiliation: University of Bayreuth, Department of Plant Physiology and Research Center of Food Quality, Universitätsstrasse 30, 95440 Bayreuth, Germany. Electronic address: stephan.clemens@uni-bayreuth.de.
authors.forename: Stephan
authors.initials: S
authors.lastname: Clemens
mesh_terms: D001383:Azetidinecarboxylic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D001682:Biological Availability; D004032:Diet; D002523:Edible Grain / Q000737:chemistry*; D005527:Food, Fortified; D006801:Humans; D007408:Intestinal Absorption / Q000187:drug effects; D007501:Iron / Q000378:metabolism*; D010833:Phytic Acid / Q000009:adverse effects; D012639:Seeds / Q000737:chemistry; D014131:Trace Elements / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism*
chemical_list: D014131:Trace Elements; C082893:nicotianamine; D001383:Azetidinecarboxylic Acid; D010833:Phytic Acid; D007501:Iron; D015032:Zinc
keywords: Elemental mapping; Intestinal absorption; Malnutrition; Metal homeostasis; Metal speciation; Nicotianamine