Novel Approaches in Mineral Fortification of Rice and Cereals

Abstract

Introduction Iron deficiency (ID) and anemia remain major public health problems affecting individuals worldwide, but particularly in low- and middle-income countries. Symptoms of ID are manifold and include fatigue, weakness and reduced work productivity. Women of child-bearing age and children are particularly prone to suffer from ID due to increased iron losses and requirements, respectively. This is the case especially in low-income countries where iron amounts provided from the diets often do not meet individuals’ needs. Food fortification is one approach to combat ID and many foods have shown to be promising vehicles for delivering iron. Rice is a major staple food for more than half the world’s population and a main source of energy in many countries, however, its micronutrient content is considerably low in its consumed form. Fortification of rice is challenging due to its white color and consumption as intact grain. Iron phosphates, particularly ferric pyrophosphate (FePP), are the most widely used iron compounds for rice fortification due to their inert sensory profile, however, iron bioavailability from those compounds is relatively low. Different technologies for rice fortification exist, but extrusion and coating have been suggested as most viable approaches. Objectives The objectives of this thesis were to a) Investigate, how iron absorption enhancers and inhibtors influence human iron absorption from rice meals containing FePP-fortified extruded rice; b) assess, whether observed inhibiting/enhancing effects from single meal administrations are also present upon multiple meal administrations; c) investigate, if the technology used for rice fortification impacts iron or zinc absorption. The generated results aim to contribute to the scientific evidence required to establish a fortification formulation that provides optimal iron supply from FePP-fortified rice. Design We conducted five different absorption studies in Swiss women of child bearing age and in Ghanaian school-age children. In study 1, we assessed the effects of citric acid in combination with trisodium citrate (CA+TSC) on iron absorption from FePP-fortified extruded rice in healthy Swiss women. Study 2 investigated the effects of the zinc co-fortificant (zinc as sulphate or oxide) on iron absorption from FePP-fortified extruded rice in iron-depleted, but otherwise healthy, Swiss women. Study 3 contained of two parts, in the first part, we investigated iron absorption in healthy Swiss women from FePP-fortified rice produced via hot or cold extrusion; in the second part we investigated iron and zinc absorption in healthy Swiss women from coated and hot extruded rice. In study 4, we investigated iron absorption from FePP-fortified rice in combination with different zinc co-fortificants (ZnO or ZnSO4) and absorption enhancers (CA+TSC, CA+EDTA) in Ghanaian school-age children, using a novel multiple-meal approach. All studies had a cross-over design, where participants acted as their own controls. Unfortified rice, where a solution of the highly bioavailable FeSO4 was added prior consumption served as a reference for fractional iron absorption (FAFe) in all, but one, studies. Furthermore, we supported our in vivo bioavailability findings with in vitro iron solubility assessments and conducted micronutrient retention tests from FePP-fortified rice manufactured via coating, hot and cold extrusion. Results Study 1 showed a significantly increased FAFe, when FePP-fortifified rice was also extruded with CA+TSC (3.2 % FAFe) compared to addition of a CA+TSC solution to the rice prior consumption (1.7 %; P < 0.05). Furthermore, FAFe in the participants did not significantly differ between the rice extruded with FePP, CA+TSC and the FeSO4-reference (1.7 %, n.s.). In study 2, we showed, that the choice of the zinc co-fortificant affects iron absorption. FAFe from FePP-fortified rice in combination with ZnO (2.7 %) was significantly lower than from ZnSO4 (4.5 %, P < 0.03). This was also reflected in iron bioavailability relative to FeSO4 (RBV) of 62 and 38 % when co-fortified with ZnSO4 and ZnO, respectively. Study 3 showed, that the extrusion conditions affect iron absorption, thus, consumption of cold extruded FePP-fortified (1.8 %) rice caused a significantly higher FAFe than of hot extruded rice (1.1 %, P < 0.05) of the same composition. No significant differences were found in FAFe from coated rice (4.0 %) versus hot extruded rice of a similar composition (5.1 %, n.s.). Similarly, no differences between fractional zinc absorption were found in coated (9.6 %) versus hot extruded rice (9.5 %, n.s.). In study 4, we found significant differences in FAFe from rice fortified with FePP co-fortified with ZnO (2.3 %) compared to co-fortification with ZnSO4 (3.5 %, P < 0.05). Addition of CA+TSC increased iron absorption in both conditions, however, absolute differences between ZnO (4.5 %) and ZnSO4 (6.3 %, P < 0.05) remained. Furthermore, we found that addition of CA+EDTA to FePP and ZnO co-fortified rice also enhanced FAFe (6.4 %). Iron absorption from FePP-fortified rice fortified with ZnO, CA+EDTA or ZnSO4, CA+TSC did not differ from the FeSO4-reference (6.4 %, n.s.). Within this study, we successfully tested a novel multiple-meal approach, in which each type of labelled test meal was given twice daily for five consecutive days providing the high precision of using stable iron isotopes, while integrating the fortified rice as a regular part of a daily consumed diet. Conclusions The results presented in this thesis, provide a solid base for future rice-fortification recommendations. The almost doubling effect on iron absorption upon addition of the absorption enhancers CA+TSC or CA+EDTA allows to reduce the quantities of fortification iron and thus to minimize the amount of unabsorbed iron. Based on the presented work, the use of such absorption inhibitors for FePP-fortified rice in combination with ZnSO4 as zinc co-fortificant is suggested. Further studies on storage stability, consumer acceptance as well as the performance of rice fortified with FePP, ZnSO4, CA and EDTA are highly recommended. Furthermore, optimal extrusion conditions regarding maximized iron absorption should be evaluated.