Some infants cannot tolerate the carbohydrate or protein in breast milk and depend upon specialized infant formula for survival. Moms who cannot breastfeed for one reason or the other (see Deciding to Breast-feed) rely on infant formula as a suitable substitute. Premature or low-birth-weight infants (under 5.5 pounds) and full-term babies who don’t gain enough weight on breast milk alone often improve when infant formula is added to their diet.

Still, there are some major nutritional differences between breast milk and formula. Generally speaking, formula contains more protein. Vitamin and mineral content can be higher, too, often to compensate for the possible lower rate of absorption of these nutrients from the formula.

Certain infant formulas are touted as low iron, yet there is rarely a medical need for low-iron formulas. In fact, inadequate iron intake can harm brain development and overall growth. That’s why the AAP is against using low-iron infant formulas. Never feed your baby a low-iron formula without the approval of your pediatrician. Form, Not Function, Is the DifferenceInfant formula comes in three forms: ready-to-feed, concentrated liquid, and powder. Price and convenience, not nutrition, are what differentiates them from each other. Convenience is costly. That’s why powdered formulas are the cheapest of all. Aside from the price break, powdered formula has other advantages, particularly for breastfeeding moms who want to supplement their milk supply. You can mix as much of the powdered formula as you need, without waste. Powdered formula preparation is more time consuming than that of the other, costlier, forms. You must measure the formula carefully, as well as boil the water to mix with it. Powders have a thirty-day shelf life after opening. The two types of liquid formula vary in concentration and cost. Concentrated liquid formula is meant to be mixed with an equal part of boiled water and delivered to baby in a clean bottle. Concentrated liquid formula is more expensive than powdered. To use ready-to-feed formula, just open and pour into a clean baby bottle. Standard Formulas Parents most often pick a cow’s-milk-based formula to nourish their infants. And with good reason. Most children thrive on a cow’s-milk formula fortified with iron. Milk-based formulas are available with little iron, or as iron-fortified, but only iron-fortified formula meets an infant’s needs for this vital nutrient. Manufacturers remove the butterfat from milk, replacing it with vegetable oil or a mixture of vegetable and animal fats. Changing the fat composition improves the digestibility and increases the concentration of essential fats needed to foster peak growth and development. Common Brand Names: Good Start (Carnation); Enfamil with Iron and Enfamil Low Iron (Mead Johnson); and Similac with Iron (Ross)