Transition from Breast Milk: When and How?

Background: Breastfeeding is the cornerstone of infant and young child nutrition with implications for long-term health and well-being. However, despite having World Health Organization guidance on the transition from exclusive breastfeeding to complementary feeding, in practice it is often fraught with challenges. This review examines the biological and clinical foundations of breastfeeding, addresses the critical questions of when and how to introduce complementary foods and discusses the gaps that hinder optimal infant feeding practices across different geographies. Finally, it highlights the pivotal role of healthcare professionals in guiding safe and responsive feeding transitions. Summary: Human breast milk is an essential component of the factors that promote optimal child health, growth and neurodevelopment. Evidence supports exclusive breastfeeding for approximately 6 months. Readiness for complementary feeding should be judged by developmental cues rather than chronological age alone. Complementary feeding introduces new nutritional and immunological demands: texture progression supports oral-motor development, timely exposure to allergens may promote tolerance, and micronutrient status is critical. Global variation in infant feeding practices reflects socioeconomic, cultural, and structural barriers that often limit adherence to guidelines. When exclusive breastfeeding is not feasible despite an optimal healthcare provider and family, partial breastfeeding or formula feeding can support infant growth. However, such decisions ideally require guidance from healthcare providers, which may not be readily accessible to all mothers. Transitioning from exclusive breast milk should be viewed as a gradual layering of foods onto an existing nutritional foundation (often provided by breast milk) rather than abrupt weaning. For maternal and child health practitioners, the priority should be to provide person-centred care that is informed by the individual circumstances of the mother-infant dyad. This includes evidence-informed practical advice that is responsive to their needs, supporting exclusive breastfeeding whenever possible, while ensuring access to safe, nutritionally adequate and sustainable alternatives where needed. Aligning health systems, community support, and policy protections is essential to enable families globally to achieve optimal feeding practices. Key Messages: Exclusive breastfeeding for about 6 months provides significant nutritional, immunological, and developmental benefits, but readiness for complementary feeding should be guided by developmental cues, not chronological age alone. Complementary feeding should emphasise iron-rich, diverse foods introduced with appropriate texture progression, alongside continued breastfeeding for sustained child health and growth. Implementation gaps persist globally largely due to unaddressed maternal challenges of navigating breastfeeding and the transition to complementary feeding. An interdisciplinary approach with mothers at the core is important in translating global guidelines into context-specific, practical guidance for families.