1. What is complementary food? 4-6 months after the baby is born, breast milk or formula milk can no longer meet the baby\’s nutritional needs. At this time, complementary food needs to be introduced. Complementary foods refer to other foods added to your baby\’s diet in addition to breast milk or formula. 2. When to start adding complementary foods. Normally, babies start to gradually add complementary foods around 4-6 months after birth. But every baby develops differently, so it\’s best to start adding them with your pediatrician\’s advice. 3. Which foods are suitable for 5-month-old babies? 5-month-old babies