Complementary Feeding: What Makes It Important

Complementary Feeding: What Makes It Important? 

Raanan Shamir 

Institute for Gastroenterology, Nutrition and Liver Diseases, Schneider Children’s medical center, Gray Faculty of Medical and Health Sciences, Tel Aviv University, Tel Aviv, Israel 

Complementary feeding (CF) is “the process starting when breast milk alone is no longer sufficient to meet the nutritional requirements of infants” so that “other foods and liquids are needed, along with breast milk CF marks a critical transition in infant nutrition, beginning when breast milk alone no longer meets the nutritional demands of growing infants. This typically occurs around six months of age, though physiological readiness—such as gastrointestinal and renal maturity—can begin as early as four months. Despite global recommendations, many infants, especially those who are formula-fed, are introduced to solids earlier than advised, often before four months. This trend is evident across various countries, including the US, Europe and Australia, raising concerns about nutritional adequacy and long-term health outcomes. 

Physiologically, infants’ gastrointestinal and renal systems are capable of handling solids by four months, but developmental readiness—such as head control, ability to sit, loss of the extrusion reflex, and interest in food, typically emerges between four and six months. Nutritionally, breast milk begins to fall short in calories, protein, iron, zinc, and vitamins A and D around six months. This is particularly critical for exclusively breastfed infants, who are at greater risk of iron deficiency 

Evidence from randomized trials suggests that introducing CF at four months does not significantly impact growth or iron status compared to exclusive breastfeeding until six months. However, the type and quality of complementary foods is important. Also, dietary diversity is a cornerstone of adequate CF The World Health Organization identified seven essential food groups that should be incorporated to ensure micronutrient sufficiency. Studies from various regions—including Africa, Asia, and Latin America—highlight the importance of diverse diets in meeting the nutritional needs of infants and young children. However, the evidence on long-term health effects of early nutritional differences remains inconclusive. 

Beyond nutrition adequacy, CF has behavioral and health benefits including, positive effect on the gut microbiome, influences the development of the gut microbiome, the development of taste and feeding preferences, learning family eating skills, allergy and obesity prevention and possibly prevention of celiac disease if gluten is introduced gradually starting with small amounts. Early and regular exposure to family foods and allergens—such as eggs and peanuts, can reduce the risk of allergic diseases. Conversely, irregular or delayed introduction may increase susceptibility, particularly in the case of cow’s milk allergy. 

Obesity prevention is another consideration. Introducing solids before four months has been associated with higher BMI in childhood. Feeding methods, such as baby-led weaning, and parental practices—especially responsiveness to satiety cues—may influence obesity risk, though current findings are mixed. Socioeconomic factors also play a role in shaping feeding behaviors and outcomes. 

In resource-limited settings, CF poses additional challenges. Poor hygiene and low-quality foods can increase morbidity from gastrointestinal infections and compromise nutritional status. WHO guidelines for children aged 6–23 months emphasize the need for hygienically safe, nutrient-dense foods, though they may lack specificity regarding allergen introduction and developmental readiness. 

Optimizing CF involves timing, content, and approach. It should begin no earlier than 17 weeks and no later than 26 weeks, with gluten introduced between four and twelve months. Breastfeeding should continue alongside CF. Foods should be rich in iron and zinc, and feeding should be guided by developmental cues and responsive parenting. Repeated exposure to new foods enhances acceptance, and healthy CF should prioritize whole, minimally processed, plant-based options without added salt or sugar. 

Ultimately, CF is not merely a nutritional milestone—it is a developmental and preventive health strategy. When thoughtfully implemented, it supports growth, immune health, taste development, and long-term dietary patterns, laying the foundation for lifelong well-being. 

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