Solid Food Considerations
How does a mother really know when her baby is ready to begin solid foods? The baby bites the breast during lactation, and seems hungry all the time, but the doctor says to wait. What other criteria should the mother look for that the doctor sees but she does not? Start with nutrition. Breast milk or formulas provide more nutrients and calories than any solid food. That means giving your baby solids before the age of 4-6 months is replacing milk with something of inferior quality. Solid food should complement breast milk or formulas, and not serve as a substitute. Starting solids any earlier also means your baby is going to get less formula or breast milk—she'll be too full for what is best for her.
Please consider that nature seems to have designed your baby to take in nothing but breast milk or formula for the first several months of life. Until your baby is 3 or 4 months old, her digestive system fails to manufacture specific enzymes, such as amylase, needed for the digestion of grains like baby oatmeal or rice. There is also the fact that her digestive tract finds it hard to digest certain fats before the age of 6 months. That means food ends up in the diaper, undigested. Proteins are also an issue. High protein foods like eggs and meat may place a strain on your baby's still-developing kidneys.
Consider also your baby's expertise as a communicator. Do you know when she's had enough to eat, or do you end feedings against her seeming inclinations? A small baby who has had enough to drink, will fall asleep or cease sucking, but to be ready for solids, your baby has to turn her head away to show you she's had enough. That won't happen before the age of 4 or 5 months, because her neck muscles just aren't ready before that time. Some people even go so far as to call infant feeding before this time "force-feeding."
It's important for the baby to have some control over the feeding process in order for her to recognize her own feelings of satiation and to become master over her self-control. Babies started too young on solids are at greater risk of becoming overweight adults, and that is due to their being fed beyond the limits of their natural appetites, again and again, as infants. Babies, like adults, should only eat when they're hungry.
Food allergies are often attributed to beginning solids too early. Allowing your child to age a bit helps him develop his immune system. Waiting a bit with introducing solids may prevent allergies and allergic reactions. Some even attribute an early start on solids as a contributory factor in becoming obese or developing asthma.
One more thing: feeding your baby solids won't make her sleep through the night. She can't do that before the age of 3 months. So even if you are very sleep-deprived, and we do sympathize, don't give in and feed her solids before that time. It won't help.
Also, think about this: if you're a breastfeeding mom, and you start your baby on solids, your milk supply may begin to diminish and your baby will begin the gradual process of weaning. It may be months before she is finished with nursing for good, but the introduction of solids into your baby's diet is where weaning begins.