The goal of this observational study is to learn how certain natural sugar components in breast milk may be linked with vitamin D level, healthy gut bacteria, and immune markers in healthy breastfed infants. The study will include exclusively breastfeeding mothers and their healthy infants aged 1 to 2 months.
The main questions it aims to answer are:
* Is this natural sugar in breast milk linked with the baby's vitamin D level?
* Is this natural sugar in breast milk linked with healthy gut bacteria?
* Is this baby's vitamin D level linked with healthy gut bacteria?
* Is this natural sugar linked with immune factors in breast milk? Participants will answer health questions from questionnaire, undergo a brief physical examination, allow breast milk and a small baby blood sample to be collected, and provide an baby stool sample.
Researchers will test these samples in the laboratory and analyze the results to answer the research questions.