Thiamine deficiency causes beriberi and is common in parts of rural Cambodia, where it appears to be a leading cause of infant death. The change in maternal and infant thiamine level after administration of thiamine to either Cambodian mothers or their infants is unknown. Normal human breast milk thiamine levels in thiamine-replete mothers are poorly characterized. The aim of this study is to determine if thiamine administered to nursing Cambodian mothers normalizes maternal and infant thiamine levels. Levels will also be obtained in nursing Caucasian mothers residing in the United States.

In this pharmacokinetic study, thiamine hydrochloride 100 mg will be administered to nursing Cambodian mothers and thiamine levels will be measured in their blood and breast milk before and after supplementation. Their infant's blood thiamine levels will also be measured. A control arm of American breast feeding mothers taking prenatal vitamins will also be enrolled, to allow comparison of maternal blood and breast milk levels between Cambodian and American mothers. Ethics committee approval was obtained in Cambodia (National Ethics Committee for Health Research #208, 2011) and in the United States (Mayo Clinic Rochester IRB #12-004047)for the Cambodian and American portions of the protocol, respectively.

Inclusion Criteria:

• Mother is at least 18 years of age
• Infant is between 1 and 12 months of age
• Cambodian infant is exclusively breast fed
• Cambodian mother has not taken vitamin supplements within the past month
• American mother has been taking prenatal vitamins throughout pregnancy and postpartum while breastfeeding
• Mother and infant do not have an acute illness at the time of enrollment
• Mother and infant are able to comply with study visits

Exclusion Criteria:

• Mother is not able to provide informed consent
• Cambodian infant has received thiamine injections within the past 2 months