Complementary feeding should be started at 6 months of age because, by this time, an infant’s nutritional needs exceed what breast milk alone can provide, particularly in terms of iron and energy. Introducing solid foods at 6 months supports proper growth, development, and prevents nutritional deficiencies. Starting earlier (before 6 months) may increase the risk of infections and digestive immaturity, while delaying beyond 6 months can lead to nutrient gaps and growth faltering. Thus, 6 months is the optimal time to introduce complementary foods alongside continued breastfeeding.

Reference: Nelson Textbook of Pediatrics, Robert M. Kliegman, 21st Edition.