Why You Should Wait Until At Least 4 Months
Reason 1. Your baby's digestive system is too immature for solid foods before 4 months. Although he can suck very well, he does not have a lot of saliva to help digest food. Until he is at least 3-4 months old, his system lacks certain digestive enzymes, such as an enzyme called amylase, needed for digesting cereals (starches or complex carbohydrates). His body has trouble digesting some fats before he is 6 months old. Some foods will pass through him undigested and end up in his diaper. And some high protein foods, like eggs, meat, and even cow's milk, given too early may cause problems with your baby's immature kidneys.
Reason 2. Your baby is not developmentally ready to eat solid foods. His throat muscles are not developed enough to swallow solid foods until he is at least 4 months old. And, it is not until about 4 months that he is able to use his tongue to transfer food from the front to the back of his mouth. In fact, when you touch his tongue, he reacts by pushing his tongue outward or forward. This response is called the extrusion reflex or the tongue-thrust reflex and it doesn't disappear until he is around 16-18 weeks old. The first time you feed him with a spoon, it may seem that he is spitting out the food and closing his mouth at the wrong time. But his tongue movement is simply the result of the not-yet-unlearned extrusion reflex and not because he doesn't want the food. It is not until he is about 5 months old that he will see the spoon coming and open his mouth in anticipation.
Reason 3. Your baby must have a way of telling you that he is satiated. He lets you know that he is finished breast or bottle feeding by stopping his sucking or by falling asleep. But until he becomes able to turn his head to refuse food, which occurs at around 4 or 5 months, he has no way of letting you know he has had enough solid food. Because of this inability, some people consider feeding solid foods to a too-young baby a method of force feeding. This practice can interfere with the body's self-regulating eating mechanism and lead to overweight later in life. As with adults, your baby should eat only when he is hungry.
Reason 4. Beginning solid foods too early has been associated with other problems later in life, such as obesity, respiratory problems like bronchial asthma, and food allergies. For more information on how food allergies are caused by too-early introduction of solid foods, see page 33.
Reason 5. Solid foods will not make your baby sleep through the night. Studies show that of all babies sleep through at 3 months of age, whether or not they are eating solid foods. Even if solid foods will help your baby sleep longer, that is still not a good reason to begin solid foods early. I know sleep deprivation is hell, and most of us have been there. Hang in there. One night he'll sleep right through, and then you can start feeling normal again.
Reason 6. If you are breastfeeding and give your baby solid foods too early, your milk production may be decreased.