Complementary feeding diet in developing countries cannot meet iron requirements of infants and young children. Iron supplementation is mostly used to treat iron deficiency whereas iron fortification is cost-effective strategy to control iron deficiency in developing countries. However, a recent study showed that iron fortification imposed negative impact on gut microbiota by increasing colonization of gut pathogen over beneficial bacteria. Gut microbiota plays essential roles in nutrient absorption, vitamin synthesis; intestinal mucosal barrier function and pathogen displacement. Iron is essential for growth and virulence of most gut pathogens and so iron supplementation might have similar negative impact on gut microbiota composition. Therefore, nutrition interventions would not be justified by assessing micronutrient status alone ignoring any possible deterioration of gut microbiota. The investigators hypothesized that optimizing the nutrient intake from locally available foods according to complementary feeding recommendation (CFR) can improve the iron status of these children while maintaining healthy gut microbiota composition.

A randomized, placebo-controlled, community-based, intervention trial will be conducted in Ayeyarwady division of Myanmar where childhood undernutrition is prevalent. The aim of this study is to compare the effect of optimized CFR to iron supplementation on iron status and gut microbiota composition of 1-2years old Myanmar children. Cluster randomization will be done at the village level to randomly allocate the villages into CFR or non-CFR villages. Individual randomization will be done to randomly assign each child into iron or placebo syrup so that individual children will receive one of 4 treatment groups (CFR, Fe, CFR + Fe, and Control) for a period of 24 weeks. Based on expected between-groups difference of hemoglobin 5g/L, at 80% power, 5% level of significance, 15% drop-out rate; after taking into account the cluster effect; required sample will be 109 per group (total = 436). A sub-sample of 15 children from each group will be randomly selected for gut microbiota assessment (total = 60). Blood samples for iron status and stool samples for gut microbiota assessment will be collected at baseline and endline. Anthropometric measurements, usual intake of iron and infectious disease morbidity will also be assessed.

Inclusion Criteria:

• Age between 12-18 months
• Apparently healthy
• Not consuming regular iron containing supplements during the last 4 months

Exclusion Criteria:

• With severe anemia (Hemoglobin < 50g/L)
• Malaria test positive with Immuno-chromatographic test (ICT)
• Mothers/ Caregivers are not willing to join the study
• Suffer from chronic diseases which can affect their dietary intake