Experts are slightly divided on this issue. Some say babies can start on solid foods as early as four months old; others say they should wait as late as six months old. Between four and six months is when babies lose their tongue thrust reflex, which causes younger babies to push food out of their mouths. Once this reflex is gone, babies can take in solids and learn to move the food back far enough to swallow.If your baby automatically pushes solid food out with his or her tongue, you’ll need to wait a few weeks and try again. Babies should also be able to hold their heads upright steady and sit with support in a high chair before eating solid foods.