RESUMEN
OBJECTIVES: We examined breast milk of mothers and urine of infants before and after introduction of supplementary foods for aflatoxin M1 (AFM1) and the association between AFM1 with maternal and infant diet. METHODS: A prospective cohort study was conducted among mothers and infants ages 0-6 months and 7-12 months from June-October 2014. Sociodemographic, dietary, birth, and health data were collected. A breast milk sample was collected from each mother and a urine sample from each infant at baseline (time point 1) and monthly for 2 time points thereafter; samples collected at baseline and time point 3 were tested for AFM1. RESULTS: Almost 5% of breast milk and 15.7% of urine samples tested AFM1-positive. The median AFM1 in breast milk was 0.020 ng/mL and in urine 0.077 ng/mg creatinine. At time point 3, infants of 5 of the 6 mothers in each group who were AFM1-positive in breast milk were also AFM1-positive in urine. Mothers' consumption of cooked maize/maize dough ≥ 3 days per week (OR 2.96, 95% CI = 1.19-7.34) and mothers' consumption of tamales made from maize ≥ 3 days per week (OR 0.28, 95% CI = 0.10-0.73) were significantly associated with AFM1 in infant urine. CONCLUSION: This is the first study in Guatemala documenting aflatoxin exposure in both breast milk of lactating mothers and infants´ urine during the first year of life. This may have important implications in understanding the multicausality of the high rates of stunting among children < 5 years old in Guatemala.