It's best to introduce solid foods when your baby's between 4 and 6 months, according to the American Academy of Pediatrics. In some cases, it's okay to begin a little later (some babies may not be developmentally ready until 7 months), but starting sooner is definitely not a good idea. Here's why:
It'll backfire. Babies are born with a reflex that makes them push their tongue forward when something touches it -- which means they can't use the tongue to move food from the front to the back of the mouth. If you try to push the food into your baby's mouth, he may start to gag, which certainly isn't going to make his first experience with solids a pleasant one. Between 4 and 6 months, this reflex disappears.
He may develop a food allergy. "The gut is much more permeable before four months, so whole proteins can be absorbed easily, which increases the risk of developing an allergy," says William Dietz, M.D., director of the division of nutrition and physical activity at the Centers for Disease Control and Prevention in Atlanta.
He doesn't need it. Up until about 6 months, breastmilk or formula provides all the nutrition he requires. After that, he'll start to need certain nutrients from solid foods. He also should get additional calories -- how many varies from baby to baby. On average, by the time he's 1, he may take in about 400 extra calories from solids; 600 by age 2.
He could acquire long-term health problems. In one study, infants fed cereal before 3 months old had a higher risk of developing celiac disease (a serious intolerance of wheat protein) than those who were fed cereal between 4 and 6 months. Studies also suggest that babies given cereal before 3 months (and, possibly, after 7 months for the first time (are at greater risk for diabetes).