What kind of complementary food should a one year and three month old baby eat? Nutrition is the basis for infant growth, especially during the period when the baby is being fed complementary foods. When your baby is one year and three months old, he has already begun to try a variety of foods. In order to provide a variety of foods, the following are the complementary food recipes recommended by nutritionists for babies one year and three months old. 1. Crushed roasted, steamed or cooked nuts Nuts are a balanced, economical and convenient food for babies. Not only do they contain important nutrients such as protein, fat, vitamins and minerals, but they also contain healthy fatty acids, antioxidants and polyphenols