2.2. Setting and Participants
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Eligible toddlers were healthy preschool-age children 12–30 months old of both sexes. Children who were taking a VD supplement and those who were clinically ill were excluded from the study. Children were recruited at eight public daycare centers in Cuernavaca, Mexico, affiliated with Secretaría de Desarrollo Social (SEDESOL).Once the principal of a daycare center agreed to participate, he or she made appointments with parents/caregivers at each daycare center. At these meetings, the project coordinator and a researcher gave the parents/caregivers a detailed explanation of the objective, methods, and risks posed by the study.