A: Craig, you're right that babies can switch from formula to cow's milk after they turn 1 year old. Currently it's recommended that they drink whole milk until their 2nd birthday, then you can give them low-fat milk.

You didn't say why your baby has been drinking soy milk formula. Was it your preference to start with it? Did you start it to see whether it helped your son's colic or diarrhea? Or did your pediatrician recommend it because your baby had an intolerance or allergy to cow's milk formula? If it was a milk intolerance or allergy, be sure to ask your pediatrician whether it's advisable to switch your baby to cow's milk, since it could precipitate the intolerance or allergy again.

If your baby was on soy formula as a preference or for colic or diarrhea (which should have passed by now), it's probably safe to switch him to cow's milk.

The best way to make the transition is to mix a small amount of cow's milk with his soy formula at each feeding, gradually increasing the proportion of milk until he becomes accustomed to drinking it. For example, you might give him one-quarter milk with three-quarters soy formula for a few days. Then switch to half milk with half soy formula for a few days. From there, change to three-quarters milk with one-quarter formula for a few days, finally making the switch to all cow's milk.

Over this time, be sure to watch your baby closely to make sure he doesn't develop any signs of milk intolerance or allergy such as abdominal discomfort, vomiting, diarrhea, skin rash or breathing problems.

If it turns out that your son can't or won't drink cow's milk, you can continue him on soy milk. Just make sure you get full-fat soy milk (containing 3 to 6 grams of fat per serving) that is fortified with calcium, vitamin D and other vitamins and minerals. After his second birthday, you can give him low-fat or fat-free soy milk.