Technical considerations for maize flour and corn meal fortification in public health: consultation rationale and summary

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1 Ann. N.Y. Acad. Sci. ISSN ANNALS OF THE NEW YORK ACADEMY OF SCIENCES Issue: Technical Considerations for Maize Flour and Corn Meal Fortification in Public Health Technical considerations for maize flour and corn meal fortification in public health: consultation rationale and summary Juan Pablo Peña-Rosas, 1 Maria Nieves Garcia-Casal, 1 Helena Pachón, 2 Mireille Seneclauze Mclean, 3 and Mandana Arabi 3 1 Department of Nutrition for Health and Development, World Health Organization (WHO), Geneva, Switzerland. 2 Flour Fortification Initiative and Emory University, Atlanta, Georgia. 3 The Sackler Institute for Nutrition Science, The New York Academy of Sciences, New York, New York Address for correspondence: Juan Pablo Peña-Rosas, M.D., Ph.D., M.P.H., Evidence and Programme Guidance, Department of Nutrition for Health and Development, World Health Organization (WHO), Avenue Appia 20, Geneva GE 1211, Switzerland. [email protected] Fortification is the purposeful addition of vitamins and minerals to foods during their industrial processing, as a way to improve the nutrition and health of populations who consume these foods. Twelve countries have mandatory maize (Zea mays subsp. Mays) flour or meal fortification. The World Health Organization (WHO) is updating evidence-informed guidelines for the fortification of staple foods in public health, including the fortification of maize flour and corn meal with iron and other micronutrients. Although there is limited experience with fortification of maize, mass fortification of maize flour with at least iron has been practiced for many years in several countries in the Americas and Africa: Brazil, Costa Rica, El Salvador, Kenya, Mexico, Nigeria, Rwanda, South Africa, Tanzania, Uganda, the United States, and Venezuela. The WHO, in collaboration with the Sackler Institute for Nutrition Science and the Flour Fortification Initiative (FFI), convened a consultation on technical considerations for fortification of maize flour and corn meal in public health in New York, New York on April 8 9, 2013 to provide input into the guideline-development process and to discuss technical considerations of the fortification processes for maize flour and corn meal. Keywords: fortification; maize; flour; corn; micronutrients Background and consultation rationale Large-scale fortification is the purposeful addition of vitamins and minerals to foods and/or condiments during their industrial processing, as a way to improve the nutrition and health of populations who consume these foods. 1 Any fortification program should be based on a demonstrated need for increasing the intake of an essential nutrient in one or more population groups. There should be clinical or subclinical evidence of the need, studies indicating low levels of nutrient intake, or the possibility of developing a deficiency owing to food habits or socioeconomic or political conditions. Seventy-eight countries worldwide legislate mandatory fortification of wheat (Triticum spp.) flour with iron and/or folic acid, long regarded as an effective public health intervention, and 12 countries do so for flour or meal produced from maize or corn (Zea mays subsp. Mays). 2 To assist countries that have been fortifying wheat and/or maize flour for decades, and for those countries that are new to fortification, recent international efforts are moving toward updating wheat and maize flour fortification guidelines. 3,4 Fortification of maize flour and products produced from maize has been implemented in several settings around the world. Although there is less experience with fortification of maize flour than of wheat flour, industrial fortification of maize flour doi: /nyas

2 Maize flour and corn meal fortification Peña-Rosas et al. with at least iron has been practiced for many years in several countries in the Americas and Africa. Voluntary fortification has been introduced in Ghana, Malawi, and Mauritania, whereas Brazil, Costa Rica, El Salvador, Kenya, Mexico, Nigeria, Rwanda, South Africa, Tanzania, Uganda, the United States, and Venezuela have mandatory fortification. 2 The way in which corn is processed and consumed varies from country to country. There are two basic categories of industrial processing employed for transforming maize into products for human consumption. They are known as wet and dry milling. In the wet-milling process, maize is separated into relatively pure chemical compound classes of starch, protein, oil, and fiber. The wet milling of maize separates much of its nutrient content from the starch component, and thus this milling is not used for small-scale production or for direct consumption. 5 Industrial dry milling includes particle size reduction of clean whole maize with or without screening, retaining all or some of the original maize germ and fiber. 6,7 The main products obtained from dry milling of corn are meal, flour, precooked meal, dry masa, and hominy flour, differing essentially in particle size. 8 In many settings, maize kernels undergo a preprocessing step before milling. This process is called nixtamalization and refers to cooking maize kernels in a dilute alkali solution (traditionally, limewater, ash, or lye). 9 After washing, the grain/kernel is dehulled by removing pericarp, leaving the endosperm and germ. Precooking is another procedure that may be applied to maize before milling and is common in some South American countries. 10 Precooked maize flour is the product obtained from white or yellow corn, composed mainly of endosperm. The kernel has been sequentially dehulled, degermed, precooked, dried, flaked, and milled. It is now recognized that there is much more variability in processing maize flour than wheat flour and that the principles that apply to wheat flour fortification may not necessarily apply to maize flour fortification. Usually, although there are some exceptions to this scenario, for a fortification program to be manageable, it is desirable that milling is centralized in few mills, because it is more difficult to implement a qualitycontrol system where milling is done at small scale. People who mainly consume locally produced, unprocessed maize meal are less likely to benefit from an industrial, large-scale, maize-fortification program. The World Health Organization (WHO) is updating several evidence-informed guidelines for the fortification of staple foods as a public health intervention, including the fortification of maize flour and corn meal with iron and other micronutrients. 3 The WHO, in collaboration with the Sackler Institute for Nutrition Science and the Flour Fortification Initiative (FFI), convened a consultation on technical considerations for fortification of maize flour and corn meal in public health in New York, New York on April 8 9, The purpose was to provide input into the guideline-development process and to discuss technical considerations of the fortification processes for maize flour and corn meal. We proposed this consultation to foster a better understanding of the industrial and regulatory issues in maize flour and corn meal fortification. To accomplish this, background documents were commissioned to experts in food technology and nutrition science on several topics for a dialogue on the implications of this intervention for public health programs and priority setting for research, and the participants included representatives from WHO Member States as well as non-state actors. The commissioned reviews aimed at summarizing different aspects of maize flour and corn meal that would be useful to inform the upcoming recommendation on the use of this intervention as a public health strategy. The topics included global maize flour and corn meal consumption; a review of the different food technologies for processing industrially produced maize flour and corn meal in different parts of the world, describing the processes to obtain precooked refined maize flour, dehydrated nixtamalized flour, fermented maize flour, and other products; the different fortification industry technologies currently available to fortify products made from corn as maize flour or corn meal and their food processing technologies from kernel to final product; a review on common changes in the stability of key micronutrients added to different maize flour and corn meal products during their addition through food processing, packaging, storage, cooking, and meal preparation; a review on the bioavailability of iron, zinc, vitamin A, and folic acid fortificants for use in fortified maize flour and corn meal and the factors that affect bioavailability of key micronutrients; models for estimating nutrient 2

3 Peña-Rosas et al. Maize flour and corn meal fortification fortification levels in different maize flours and corn meals; a review on the legal framework for maize flour and corn meal production; the economic feasibility of industrially fortified maize flour and corn meal in different contexts; and a review of the factors that determine the differential availability, accessibility, acceptability, effective usage, consumption, and impact of fortified maize flour and corn meal across social groups. The consultation was structured to provide an overview on several topics of relevance to maize flour and corn meal fortification with micronutrients in public health. Twelve experts spoke on the specific objectives of the consultation and facilitated discussions, focusing on different aspects of maize flour and corn meal fortification in public health. For clarity, we have separated this paper in two sections: (1) summary of presentations and (2) research priorities and technical considerations. Summary of the presentations Public private civic partnerships for maize flour and corn meal fortification Public private partnerships are ongoing agreements between government and private sector organizations in which the private organization participates in the decision making and production of a public good or service that has traditionally been provided by the public sector, and for which the private sector shares the risk of that production. These agreements among partners need not be formal. They can be loose informal arrangements where all the partners agree to work together toward a common goal. The FFI, for example, has a role in stimulating the public, private, and civic sectors to work together to promote, implement, and monitor fortification programs in countries. The main reason to enter into public private partnerships is to combine skills, expertise, and other resources to achieve a common goal that is unattainable through independent action. Successful large-scale fortification requires such partnerships. Previous experiences, such as fortification of salt, oil, and wheat flour, have generated lessons learned that can be applied to accelerate maize flour and corn meal fortification. Partnerships established for these foods, such as the National Fortification Alliances, can be tapped and broadened to include relevant maize flour and corn meal partners. 11 Champions of fortification are critical to make maize flour and corn meal fortification successful. Global maize flour and corn meal consumption Fortification of maize flour and corn meal can be considered in any country where maize is an important food staple. The worldwide market of maize flour and corn meal and its characteristics and trends were described. A major distinction in the type of milled maize product is particle size. Another difference is the extraction rate, as both highand low-extraction products are made. As with all cereals, most micronutrients are concentrated in the outer layers of the grain; thus, removing these layers in the milling process results in the loss of most vitamins and minerals. These losses, however, can be replaced through fortification without affecting the quality or acceptability of foods made from maize flour or corn meal. High-extraction products include all or part of the germ, which give them a high fat content and a shorter shelf life. In Africa, the most common commercially milled products are of low extraction. Considerations about the wide range of maize products based on continental, regional, and national practices, such as porridges, fermented porridges, and tortillas of different types, and maize products that are currently fortified through mandatory or voluntary schemes, were discussed. 12 Maize flour and corn meal processing worldwide Food technologies for processing industrially produced maize flour and corn meal in different parts of the world were presented and discussed. There are several processes applied to maize before and after milling. These processes affect particle size, nutrient losses, and contents, which are relevant in the fortification process. Milling degermed maize has different processes than those for obtaining precooked refined maize flour, dehydrated nixtamalized flour, fermented maize flour, and other products. 13 Fortification technologies for maize flour and corn meal Technologies are available to fortify products made from maize, such as maize flour or corn meal. These are applied from the kernel to the final product. It should be noted that maize flour and corn meal products can be obtained from the most 3

4 Maize flour and corn meal fortification Peña-Rosas et al. rudimentary milling equipment up to the equivalent level of sophistication used in industrial wheat milling. Details about fortification technologies, types of milling, and mixing procedures were presented. Although wheat and maize fortification can use the same techniques for fortification, the maize milling sector is considerably different, in many countries, from the wheat sector. Maize flour or corn meal products are significantly less constrained, resulting in the ability to produce maize meal on milling equipment with different levels of sophistication. Fortification technologies fall into one of two broad classifications (with numerous variants) and are designed to add a known quantity of fortification premix to a known quantity of maize flour or corn meal: batch mixing or continuous mixing. A considerable amount of milling is, however, done at the village level or in small-scale milling operations using hammer mills. It has long been recognized that getting fortification into rural areas is one of the greatest challenges facing any fortification program. The number of small mills without fortification technology needs to be assessed to decide if fortification of maize flour is a feasible option for a particular country. Quality and stability of key micronutrients in fortified maize flour and corn meal The stability of key micronutrients added to maize flour and corn meal during manufacturing, packaging, distribution, storage, cooking, and as part of a whole meal were presented with special emphasis on iron, zinc, calcium, and vitamins B 1 (thiamin), B 2 (riboflavin), B 3 (niacin), B 6 (pyridoxine), B 9 (folic acid), B 12 (cobalamin), A, and D 3. Findings indicate significant losses in B vitamins (B 1,B 2,B 3,B 6,B 9, and B 12 ) during manufacturing, distribution, and cooking. Vitamins A and D 3 are recent additions to fortification premixes for maize and have not been well studied. 14 In terms of minerals, iron, zinc, and calcium are low in maize and maize/corn products, with small losses occurring during milling. Calcium increases with nixtamalization because of the calcium hydroxide added. Sieving and reconstituting mill fractions may also result in decreases in the mineral and vitamin content in the final flour. There are limited studies of maize flour and corn meal assessing the stability of micronutrients during storage, processing, preparation, and cooking, but the availability of studies on corn soy blends, wheat, and rice could be useful to gain insights into the importance of considering the stability of micronutrients in public health programs. Micronutrient bioavailability from fortified maize flour and corn meal: iron, zinc, folic acid, and vitamin A The bioavailability of micronutrients refers to the proportion of the micronutrient capable of being absorbed and available for use or storage in the body. The bioavailability of micronutrients in fortifiedmaizeflourandcornmealwasdiscussed.iron sodium ethylenediaminetetraacetic (NaFeEDTA), ferrous fumarate, and ferrous sulfate are used to fortify maize flour or corn meal. The choice of zinc fortificant appears to have a limited impact on zinc bioavailability. Added minerals (iron, zinc, calcium) are generally retained after industrial processing, although phytic acid in corn may affect bioavailability. Degermination at the mill will reduce not only phytic acid content, but also native mineral and vitamin content. Enzymatic phytate degradation may be a suitable home-based technique to enhance the bioavailability of iron and zinc from fortified maize flourandcornmeal.reductionofphytatecontent by endogenous or exogenous phytase can be an effective strategy to improve bioavailability. Folic acid and encapsulated retinyl ester offer satisfactory bioavailability, which is in large part independent of the food vehicle. Folic acid bioavailability from fortified maize flour and corn meal may be in the same range as in fortified wheat flour. The bioavailability of vitamin A as encapsulated retinyl esters is generally high and it is typically not influenced strongly by the food matrix, but this has not been investigated in maize. 15 Optimizing maize flour fortification standards for correcting micronutrient inadequacies in Sub-Saharan Africa and Latin American regions A model for estimating nutrient fortification levels proposes the use of average maize flour intake while considering the variation in food-consumption patterns among different population groups. A general procedure to design safe and efficacious food fortification programs was described using data from food consumption surveys from Uganda and Mexico. The model is based on approximating the magnitude of the nutritional inadequacy of the population and 4

5 Peña-Rosas et al. Maize flour and corn meal fortification the optimal use of the combination of various food vehicles, and assures that additional intake is below the tolerable upper intake level of the individuals with the highest combined intake of all food vehicles. The model has been developed to be applied when detailed food intake data are not available, but goes beyond the simple per capita food intake use. 16 Maize flour fortification standards and regulations: gaps and limitations in Sub-Saharan Africa and Latin American regions A model of fortification legislation (including standards) was presented based on the identification of gaps and limitations after reviewing a number of national standards and regulations of fortified corn flour and maize meal. In the model legislation (including standards), the additional nutrient content and the expected average nutrient content in the final product are recommended as the main parameters for quality control and enforcement. Variation in the micronutrient contents is checked to ensure homogeneity following clear procedures of sampling and testing, which are part of the standards and regulations. 17 Assessing the economic feasibility of maize flour and corn meal fortification: evidence from Zambia, Kenya, and Uganda There are various dietary, logistical, and economic issues involved in assessing the need for and feasibility of maize flour fortification. This was assessed in three African countries: Kenya, Uganda, and Zambia. Critical factors that must be evaluated to assess the feasibility and sustainability of maize flour fortification include the level of consumer demand andtypeofconsumption,quantityoflocalmaize production, existing mill technologies, coverage, and changes in price due to fortification. 18 Determinants of equity in access to fortified maize flour and corn meal The long-term sustainability of fortification programs is ensured when consumers are willing and able to bear the additional cost of fortified foods. In contexts of extreme and extended poverty and lack of opportunities, guaranteeing access to fortified foods requires addressing the factors that allow for the reproduction of exclusion and poverty, which are socially determined and thus modifiable. Equity aspects can be comprehended using a socialdeterminants-of-health perspective, through a conceptual framework of equity in access to fortified maize flour and corn meal with information on the different levels included in the framework. 19 Cochrane protocol: fortification of maize flour with iron for preventing anemia and iron deficiency in populations A systematic review of evidence is underway to determine the benefits and harm of iron-fortified maize flour and corn meal and foods made from these (i.e., fortified maize flour products) for anemia and iron status among the general population. Fortification of maize flour is an intervention that aims to reach the entire population of a country or large sections of the population and is frequently delivered through the market system. This review includes randomized controlled trials and, in addition, plans to examine data from other study designs. The interventions to be included in this review are those in which maize flour, corn meal, and/or maize subproducts have been fortified with iron alone or iron plus other vitamins and minerals. Composite flour that contains more than 50% maize will be included within the definition of flour in this review. Maize flour products include all products derived from fortified corn meal and flour (i.e., breads, cereals, polenta, porridges, grits, arepas). Four comparisons will be made: (1) maize flour, corn meal, or maize flour products fortified with iron alone versus no intervention; (2) maize flour, corn meal, or maize flour products fortified with iron plus other vitamins and minerals versus no intervention; (3) maize flour, corn meal, or maize-flour products fortified with iron alone versus unfortified maize flour, corn meal, or maize flour products (not containing iron or any other vitamin and mineral); and (4) maize flour, corn meal, or maize flour products fortified with iron plus other vitamins and minerals versus unfortified maize flour, corn meal, or maize flour products (not containing iron or any other vitamin and mineral). 20 Maize flour fortification with folic acid: the U.S. experience Cornmasaflour,usedtomakeproductssuchascorn tortillas, is a staple food in Hispanic populations residing in the United States, particularly those from Mexico and Central America. Corn masa flour has been suggested as a potential food vehicle for folic acid in the United States to reduce the disparity in 5

6 Maize flour and corn meal fortification Peña-Rosas et al. folic acid intake in the Hispanic population. This policy-level intervention would require a change in federal regulations but could potentially reduce the number of neural tube defects among Hispanic women and increase total folic acid intake among this at-risk population. 21 Research priorities and technical considerations for maize flour and corn meal fortification Research priorities for maize flour and corn meal fortification There are barriers and opportunities for the inclusion and use of fortified maize flour and corn meal in public health and social development programs. Some of the barriers include weak or nonexistent enforcement of regulations, inadequate nutrient levels or compounds, low consumption of foods to be fortified, poor manufacturing techniques and standards, weak or nonexistent quality-control systems, lack of continuity of efforts (sustainability), and changes in policies. Discussion among participants highlighted the limited evidence available in some areas, meriting further research on maize flour and corn meal fortification. These areas include the bioavailability of iron compound mixes for use in the fortification of maize flour and corn meal produced with different technological processing, the bioavailability and stability of folic acid and vitamin A in maize flour and corn meal with different maize flour processing methods (i.e., nixtamalization), the impact of maize for biofuel production on food security and for sustainability of a maize flour and corn meal fortification program, and the feasibility of small-scale fortification of maize flour and corn meal for public health programs. Technical considerations for maize flour and corn meal fortification in public health On the last day of the meeting, five multisectoral working groups met to discuss technical considerations for maize flour and corn meal fortification in public health programs. Several considerations were made for program implementers and maize flour and corn meal stakeholders in relation to the use of this intervention. The main considerations from those working groups are summarized below. Maize flour and corn meal have different characteristics in relation to extraction rate, particle size, fat, protein, and fiber content. For example, the characterization of grits, meal, fine meal, and flour differ from country to country. Thus, terminology is not uniform, nor are the extraction rates in different countries. In addition, a variety of products are made from maize, some of which go through dry milling or undergo some processing before consumption at the household level. Maize flour and corn meal are processed into several different products, including degermed flour (the most similar to refined wheat flour), precooked maize flour, whole flour, and lime-treated (nixtamalized) flour. Technological issues specific to fortification of maize flour and corn meal must be fully resolved, especially with regard to appropriate levels of nutrients, nutrient interactions, and physical properties. In addition, it is important to assure food product acceptability by consumers. Decisions about which nutrients to add and the appropriate amounts to add to fortified maize flour and corn meal must be guided by the nutritional needs of the population, the usual consumption profile of maize flour or corn meal that can be realistically fortified, sensory and physical effects of the nutrient compounds on maize flour or corn meal products, fortification of other food vehicles, population consumption of vitamin and mineral supplements, and costs and equity considerations. The selection of the type and quantity of vitamins and minerals to add to maize flour and corn meal, either as a voluntary standard or a mandatory requirement, lies with national decision makers in each country, and therefore the choice of compounds as well as quantities should be viewed in the context of each country s situation. Maize flour and corn meal fortification must be designed in the context of fortification (both voluntary and mandatory) of other food vehicles (i.e., salt, wheat flour, rice) so as to improve efficiencies while assuring safety. Fortification of maize flour and corn meal in countries where these are staples andarewidelydistributedandconsumedcouldpotentially improve the nutritional status of a large proportion of the population, and guidelines for its use in public health are required. Fortification programs that involve maize flour and corn meal could be expected to be most effective in achieving a public health impact if mandated at the national level in countries where these are staples consumed by large segments of the population. 6

7 Peña-Rosas et al. Maize flour and corn meal fortification Finally and importantly, monitoring and evaluation are essential components of any fortification program, including maize flour and corn meal fortification. The program evaluation has to go beyond biomarker assessment and include coverage and change in nutrient intake. Conflicts of interest Helena Pachón works as a senior nutrition scientist for the FFI, an international partnership working to improve health by advocating for fortification in industrial mills, specializing in wheat flour, maize products, and rice. She oversees the scientific evidence on the benefits of flour fortification and evaluating the public health impact of flour fortification. The other authors declare no conflicts of interest. Acknowledgments All authors have read and approved the final manuscript.helenapachón s time was supported by an appointment to the Research Participation Program at the U.S. Centers for Disease Control and Prevention (CDC), administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the U.S. Department of Energy and the CDC. Juan Pablo Peña-Rosas is a staff member of the WHO. The authors alone are responsible for the views expressed in this article and they do not necessarily represent the decisions, policy, or views of the WHO. References 1. Allen, L. et al., Eds Guidelines on Food Fortification with Micronutrients. Geneva: World Health Organization and Food and Agricultural Organization of the United Nations. 2. Flour Fortification Initiative (FFI). Global progress. April index.php. Accessed April 2, WHO, FAO, UNICEF, GAIN, MI, & FFI Recommendations on Wheat and Maize Flour Fortification. Meeting Report: Interim Consensus Statement. Geneva: World Health Organization. lications/micronutrients/wheat_maize_fortification/en/. Accessed April 2, Peña-Rosas, J.P., L.M. De-Regil, L.M. Rogers, et al Translating research into action: WHO evidence-informed guidelines for safe and effective micronutrient interventions. J. Nutr. 142: 197S 204S. 5. USDA. United States Department of Agriculture. Grain inspection, packers & stockyards administration. United States standards for corn. April 1, gipsa.usda.gov/fgis/standards/810corn.pdf. 6. Rooney, L. & S. Serna-Saldavar Food Uses of Whole Corn and Dry-Milled Fractions in Corn: Chemistry and Technology. S.A. Watson & P.E. Ramstad, Eds. St. Paul, MN: American Association of Cereal Chemists. 7. Brubacher, T Dry corn milling: an introduction. Technical Bulletins. International Association of Operative Millers. pp Dale, E. & F.F. Niernberger Economic models of dry corn milling: part I-model design and system specifications. Assoc. Oper. Millers Tech. Bull. Dec Bressani, R., J.C. Turcios, A.S. Colmenares de Ruiz & P.P. de Palomo Effect of processing conditions on phytic acid, calcium, iron, and zinc contents of lime-cooked maize. J. Agric. Food Chem. 52: Gould, M.R., L.P. Carroll & C. Ralph Process for preparing a pre-cooked corn flour. United States Quaker Oats Co Pachon, H. Public-private-civic partnerships for maizeflour and corn-meal fortification. February 25, Flour Fortification website org/about/calendar/2013/documents/maize_partnerships. pdf. Accessed April 2, Ranum, P., J.P. Peña-Rosas & M.N. Garcia-Casal Global maize production, utilization, and consumption. Ann. N.Y. Acad. Sci. 1312: Gwirtz, J.A. & M.N. Garcia-Casal Processing maize flour and corn meal food products. Ann. N.Y. Acad. Sci. 1312: Dunn, M.L., V. Jain & B.P. Klein Stability of key micronutrients added to fortified maize flours and corn meal. Ann. N.Y. Acad. Sci. 1312: Moretti, D., R. Biebinger, M.J. Bruins, et al Bioavailability of iron, zinc, folic acid, and vitamin A from fortified maize. Ann. N.Y. Acad. Sci. 1312: Guamuch, M., O. Dary, Z. Rambelson, et al Model for estimating nutrient addition contents to staple foods fortified simultaneously: Mexico and Kampala data. Ann. N.Y. Acad. Sci. 1312: Makhumula, P., O. Dary, M. Guamuch, et al Legislative frameworks for corn flour and maize meal fortification. Ann. N.Y. Acad. Sci. 1312: Fiedler, J.L., R. Afidra, G. Mugambi, et al Maize flour fortification in Africa: markets, feasibility, coverage, and costs. Ann. N.Y. Acad. Sci. 1312: Zamora, G. & L.M. De-Regil Equity in access to fortified maize flour and corn meal. Ann. N.Y. Acad. Sci. 1312: Pasricha, S.-R., L.M. De-Regil, M.N. Garcia-Casal, et al Fortification of maize flour with iron for preventing anaemia and iron deficiency in populations. Cochrane Database Syst. Rev. 11 doi: / CD Hamner, H.C. & S.C. Tinker Fortification of corn masa flour with folic acid in the United States: an overview of the evidence. Ann. N.Y. Acad. Sci. 1312: