Iron bioavailability of Ferric Pyrophosphate in fortified, extruded rice increased by pre-treatment with a citrate buffer

By Rob Winwood

Deficiency of iron in the diet is considered the most common cause of anaemia in both developing and industrialised countries (2).  Anaemia due to iron deficiency is of particular concern in children and women of childbearing age as it adversely affects the child’s development and immunological status.

Rice is a widely consumed staple food throughout the world. Hence, rice fortification with iron is an effective approach in the prevention of anaemia in at-risk populations (3).

Ferrous sulphate solution can be easily added to ground rice prior to extrusion and while the iron in the final rice product is highly bioavailable, it also causes an unsightly brown discoloration which severely limits its acceptability. As an alternative, ferric pyrophosphate (FPP) addition provides a stable, organoleptically acceptable rice, but suffers from poor bioavailability. It is not possible simply to increase the dose, as higher levels of iron reaching the colon cause adverse effects on the gut.

A new study from the Swiss Federal Institute of Technology in Zürich (1) has demonstrated how the bioavailability can be dramatically improved by the addition of an inexpensive citrate buffer. The trisodium citrate/citric acid buffer enables the FPP to be brought into solution during the extrusion cooking. Previously an attempt to achieve this with an ethylene-diamine-tetraacetic acid (EDTA) buffer has failed (4).

In the Swiss study, the bioavailability of the citrate buffer treated FPP extruded rice (in an isotope form) was verified by measuring the blood iron status of 20 young women subjected to three test rice meals over a total of 44 days and comparing it with baseline measurements. The citrate buffer nearly doubled the fractional iron absorption – from 1.7% to 3.2% - and made it closely comparable to the reference ferrous sulphate treatment (3.4%).

Hence, the authors recommend the widespread use of these inexpensive citrate buffers in the production of iron-fortified rice.

1. Hackl L, Cercamondi CI, Zeder C et al.; “Cofortification of ferric pyrophosphate and citric acid/trisodium citrate into extruded rice grains doubles iron bioavailability through in situ generation of soluble ferric pyrophosphate citrate complexes”; The American Journal of Clinical Nutrition 2016, (C), 1–8. http://doi.org/10.3945/ajcn.115.128173
2. Kassebaum NJ, Jasrasaria R, Naghavi M et al.; “A systematic analysis of global anemia burden from 1990 to 2010”; Blood 2014; 123: 615-24.
3. Gera T, Sachdev HS, Boy E; “Effect of iron-fortified foods on hematologic and biological outcomes: systematic review of randomized controlled trial”; Am J Clin Nutr 2012; 96: 309-24.
4. Hurrell RF, Reddy MB, Burri J et al.; “an evaluation of EDTA compounds for iron fortification of cereal-based foods”; Br J Nutr 2000; 84: 903-10.