Different Types of Infant Formulas

Most formulas are made with cow's milk, with various ingredients to make them taste more like breast milk. In her book, "Natural Baby and Childcare," Lauren Feder, M.D., offers some formula factors to look for, including DHA-enriched, which means it contains Omega-3 fatty acids that have been shown to boost infant eyesight and brain development; the ratio of proteins whey and casein--an 80 percent whey to 20 percent casein ratio best resembles breast milk; and iron-fortified, because it's harder for babies to absorb iron from formula than breast milk.

Soy-based formulas have their place, but not a very big one it seems. A 2008 study published by the American Academy of Pediatrics (AAP) states: "There are few indications for their use in place of cow milk-based formula." In fact, the AAP offers just two uses: for infants with certain rare conditions called galactosemia and hereditary lactase deficiency, or if a family adheres to a strict vegetarian diet. Some people incorrectly believe that babies who are allergic to milk-based formulas will do better on soy-based. Actually, according to Dr. Feder, up to 50 percent of babies allergic to cow's milk are also sensitive to soy milk.

For babies who show extreme allergic reactions to milk- or soy-based formulas or have a family history of severe allergies to them, pediatricians may recommend a hypoallergenic formula. The protein in this type of formula is already broken down, so it's easier to digest. Unfortunately for the baby, it also tends to be more bitter than the others.

Depending on your need for convenience or frugality, you can choose from three major forms of formula. Powdered is least expensive, but can be a hassle when on the go. Concentrated liquid must still be mixed with water, though may blend quicker. Ready-to-use formula is the most convenient and most expensive.