Our study will be done in a subgroup (n=160) of a larger double-blind controlled feeding trial in which 330 infants will be randomized to receive a micronutrient powder containing either 2.5 mg iron or no iron for 1 year. In our substudy, the infants will be studied only over the first 6 months of the 1 year intervention. Blood samples, taken at baseline and after 6 months will be used to define the iron status and the anemia level of the infants. Stool samples (2 at baseline before intervention, 6 throughout the study and additional samples in case of diarrhea) will be obtained for analysis of the gut microbiota. In the entire study (n=330), we will measure changes in iron status over 1 year.