The World Health Organization recommends exclusive breastfeeding until 6 months followed by introduction of iron-rich complementary foods (CFs). The aim of this study was to determine the impact of different iron-rich CFs on infant gut inflammation and microbiota. Eighty-seven exclusively breastfed infants were randomly assigned to receive one of the following as their first CF: iron-fortified cereal (Cer), iron-fortified cereal with fruit (Cer + Fr), or meat (M). Urine and stool samples were collected to assess reactive oxygen species (ROS) generation, gut microbiota and inflammation. Fecal iron differed across feeding groups (p < 0.001); levels were highest in the Cer group and lowest in M group. A significant increase of fecal ROS formation (p < 0.002) after the introduction of CFs was observed, but did not differ across feeding groups. Fecal calprotectin increased within all groups after the introduction of CFs (p = 0.004). Gut microbiota richness increased after introduction of M or Cer + Fr. Regardless of feeding group, Coriobacteriaceae were positively correlated with ROS and Staphylococcaceae were negatively correlated with calprotectin. Choice of first CF may influence gut inflammation and microbiota, potentially due to variations in iron absorption from different foods. Further research is warranted to fully characterize these associations and to establish implications for infant health. This study was registered in the ClinicalTrial.gov registry (Identifier No. NCT01790542 ). This study was registered in the ClinicalTrial.gov registry under the name “Assessment of Complementary Feeding of Canadian Infants” (Identifier No. NCT01790542 ) February 6, 2013.

Despite a World Health Organization recommendation for exclusive breastfeeding of all full-term infants to 6 months of age, it is not clear what the health implications may be. Breast milk alone may not meet the nutrition needs for all growing infants, leaving them at risk for deficiencies. The objective of this study was to investigate the relationship between moderate (4 months) versus late (6 months) introduction of complementary foods to the full-term breastfed infant on iron status and growth. An electronic search of peer-reviewed and gray-literature was conducted for randomized control trials (RCTs) and observational studies related to the timing of introduction of complementary foods. Iron status and growth data from the relevant RCTs were analyzed using RevMan 5.2.11. Three RCTs and one observational study met the inclusion criteria. Meta-analysis showed significantly higher hemoglobin levels in infants fed solids at 4 months versus those fed solids at 6 months in developing countries [mean difference [MD]: 5.0 g/L; 95 % CI: 1.5, 8.5 g/L; P = 0.005]. Meta-anaysis also showed higher serum ferritin levels in the 4-month group in both developed and developing countries [MD: 26.0 μg/L; 95 % CI: -0.1, 52.1 μg/L, P = 0.050], [MD: 18.9 μg/L; 95 % CI: 0.7, 37.1 μg/L, P = 0.040]. Short follow-up periods and small sample sizes of the included studies were the major limitations. RCT evidence suggests the rate of iron deficiency anemia in breastfed infants could be positively altered by introduction of solids at 4 months.

The first 6 months of life is a crucial time in meeting iron needs. The purpose of this review is to examine iron in mother’s milk and whether or not it meets the physiological needs of the growing infant. Key issues include iron content and iron transport from the mammary gland as well as when and what foods should be added to the solely breastfed infant. We examine these topics in light of new molecular biology findings in the mammary gland.

Background: Iron is an essential nutrient for normal growth and neurodevelopment of infants. Iron deficiency (ID) remains the most common micronutrient deficiency worldwide. There are convincing data that ID is associated with negative effects on neurological and psychomotor development. Objectives: In this review, we provide an overview of current knowledge of the importance of iron in normal term breast-fed infants with a focus on recommendations, metabolism, and iron requirements. Conclusions: Health organizations around the world recommend the introduction of iron-rich foods or iron supplements for growing infants to prevent ID. However, there is no routine screening for ID in infancy. Multicenter trials with long-term follow-up are needed to investigate the association between iron fortification/supplementation and various health outcomes.