It is uncertain whether fortifying maize flour with iron and other vitamins and minerals reduces the risk of iron deficiency. The evidence is also too uncertain to conclude whether iron-fortified maize flour, corn meal or fortified maize flour products have any effect on reducing the risk of anaemia or on improving haemoglobin concentration in the population. We do not know whether fortifying maize flour with iron reduces anaemia in the general population, as the evidence was very unreliable. No studies reported on any harmful effects. What was studied in the review? Approximately 496 million non-pregnant women, 32 million pregnant women, and 273 million children were thought to be anaemic as of 2011. Iron deficiency is considered to be the single most prevalent nutrient deficiency worldwide, but at least half this burden is considered responsive to interventions that involve providing people with iron. Fortification means adding vitamins and minerals to foods to increase their nutritional value. In public health, fortifying staple foods is considered one way of reducing micronutrient deficiencies without changing usual and culturally acceptable diets. Maize (corn) is one of the world's most important cereal grains. In sub-Saharan Africa, some parts of Southeast Asia and Latin America, where iron deficiency is endemic, maize is a dietary staple for more than 200 million people. Fortification of maize flour with iron (and in some cases, other nutrients) is mandatory in Brazil,