A mom of two with a doctorate in perinatal nutrition, I’m known as “The Baby Formula Expert” — here to help demystify the process of choosing a formula.

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Photography by Aya Brackett

Standing in the baby formula aisle for the first time can feel like a game of Russian roulette.

Was that too morbid? Probably. But I know firsthand the overwhelming intensity of that choice and how high the stakes are. We’re talking about your precious baby’s nutrition and comfort! Parenting is hard enough — and then you find yourself in the formula aisle.

Many parents admit feeling anxious about how to go about choosing a formula. Maybe they’re totally overwhelmed by the choices. Or they’ve tried a formula and wonder if it’s causing their baby digestive distress. Or breastfeeding isn’t working out how they’d hoped, and this isn’t what they expected.

No parent deserves all that anxiety over feeding. So first, take a deep breath. There is no wrong choice! There is no perfect formula. There is no “bad” formula. There are just different options within ingredient categories. Understanding these options will help you make a choice based on your unique baby.

Protein, carbohydrate, and fat make up 98 percent of infant formula. Protein and carbohydrates have the most impact on your baby’s comfort while digesting, so I always recommend parents choose a formula based on these ingredients.

You can literally ignore the front of the formula label. What a relief! These labels are full of competing messages. Words like “sensitive” and “gentle” are not regulated and don’t mean anything.

Instead, flip over the can and look at the list of ingredients. Focus on the first few ingredients before the “less than 2%” long list of vitamins and minerals. Those first few ingredients will tell you what type of protein and carbohydrates are used in that formula.

Yes, there’s both dairy-based and soy-based formula. But the more important digestion question is: How BIG are the proteins your baby is drinking?

Standard (full-size) protein formula

Standard formulas do not process the protein at all. They are exactly the size they were when they came out of the cow or soybean. That size is big. Cow’s milk and soy proteins are much bigger than breast milk proteins. If they were a car, they’d be a monster truck.

You will see full-size proteins on the list of ingredients as: “nonfat milk”, or “milk protein isolate,” or “whey protein” (a component of cow’s milk protein), or “soy protein isolate” in soy formulas. These formulas are the standard formulas with full-size proteins.

Most healthy babies handle these big proteins just fine! However, they do take more digestive work to absorb.

Partially hydrolyzed protein formula

Partially hydrolyzed protein is smaller. Hydrolyzed literally means “broken apart.” The proteins in partially hydrolyzed formulas are broken down to be smaller in size, closer to the size of breast milk proteins. If these proteins were a car, they’d be a Honda Civic.

On the list of ingredients, you will see the words “partially hydrolyzed” in front of the protein. For example, Enfamil Gentlease is a partially hydrolyzed formula, and the list of ingredients includes “partially hydrolyzed nonfat milk.”

The only real way to know if a formula is partially hydrolyzed is to look for those words on the ingredients list. For instance, Gerber Good Start Soy formula is a partially hydrolyzed protein, which is different than the full-size soy protein in Enfamil ProSobee and Similac Soy Isomil.

Because partially hydrolyzed proteins take less digestion to be absorbed, they may be a good choice for some newborn infants or infants who are experiencing discomfort digesting the full-size proteins, or who have a history of digestive issues.

Fully hydrolyzed protein formula

Fully hydrolyzed proteins are tiny. If you can partially hydrolyze a protein, then (you guessed it) you can fully hydrolyze a protein! In our car analogy, fully hydrolyzed proteins are more like a skateboard.

Fully hydrolyzed proteins are also hypoallergenic. These protein pieces are so small, they won’t trigger an allergy in a child who is allergic to full-size cow’s milk protein. You’ll see the word “hypoallergenic” clearly on the front of the can.

These formulas are for infants with a cow’s milk allergy or babies who have had severe digestive issues. But these are not common issues. For that reason, fully hydrolyzed formulas are specialized enough that you should not just try them without a doctor specifically recommending it.

Lactose is the carbohydrate source in breast milk, and all healthy babies are able to digest lactose. If your healthy baby is starting off on formula for the first time, I say start with a lactose-based formula and see how it goes.

There are reasons that some babies thrive on a formula that is lactose-reduced. Babies who were born early or who have immature or irritated digestive tracts may make less of the enzyme that digests lactose.

Babies recovering from diarrhea or babies who have been consuming low-lactose formulas for a long time will also have less lactose-digesting enzymes and may be more comfortable on a lactose-reduced formula.

If lactose is removed from a formula, some other carbohydrate must be added to ensure babies get enough carbohydrate energy. There are only two other carbohydrates small enough that infants can digest them well. These are sucrose (table sugar) and glucose sugars.

While both are deemed safe for babies, my personal preference is glucose sugars. There are several different types of glucose sugars used in formulas these days, including: corn syrup, corn syrup solids, brown rice syrup, glucose syrup, and maltodextrin.

The only way to know if a formula is lactose-reduced is to look for these other carbohydrate sources on the list of ingredients.

The variety of protein options layered on top of the variety of carbohydrate options results in the large number of formulas that overwhelm you at Target. But now you know how to pick your formula based on the protein and carbohydrate ingredients.

Prioritize your protein choice first since protein is the most likely factor affecting digestibility and comfort. From options with the protein source you are looking for, pick the formula with the carbohydrate blend closest to what you want. Then give it a shot.

You made your decision based on science. If you need to change formulas in the future, you know how to select your next formula the same way. That’s the best you can do.

I can’t emphasize enough that there is no “perfect” formula. Every baby is unique! This means the “best” formula for your baby is likely totally different than the “best” formula for your neighbor’s kid or your favorite celebrity.

If you want to start or switch formulas, talk to your pediatrician. Here are some suggestions that might help that conversation.

If your baby has reflux

Reflux — or chronic spitting up — is rough! There is sadly no magic pill to make it go away. But you might consider a formula with a high whey content.

Milk proteins come in two categories: whey and casein. Whey proteins stay liquid in the stomach and so empty out of the stomach more quickly. Enfamil Infant is a full-size protein formula that is 60 percent whey — the highest whey in the full-size protein category.

Gerber Good Start GentlePro, Gerber Good Start SoothePro, and Similac Pro-Total Comfort are all formulas in the partially hydrolyzed category that are each 100 percent whey.

You could also consider a thickened formula for reflux. Similac for Spit Up and Enfamil AR each add thickeners to the formula so that gravity works with the baby to help keep contents in the stomach.

These formulas are each full-size protein formulas that are mostly casein protein. Thus, thickened formulas may potentially help reflux symptoms for a different reason than whey-predominant formulas.

If you’re dealing with baby eczema

Partially hydrolyzed protein formula has been shown to help infant eczema. Similac Pro-Total Comfort and Gerber Good Start GentlePro and Gerber Good Start SoothePro all have the same protein base – partially hydrolyzed whey.

Enfamil Gentlease and Enfamil Reguline use a partially hydrolyzed mix of two types of proteins found in cow’s milk — whey and casein proteins. One is not better than the other. They are just different, and different babies may thrive on one versus the other.

So if you start with Gerber Good Start GentlePro and things improve but you think your baby can be even more comfortable, then consider trying Enfamil Gentlease to see if that difference in protein source helps your baby digest more easily.

If your baby is constantly constipated

If your baby really suffers from constipation, then ask your doctor about switching to a formula that does not contain palm oil.

Palm oil can cause babies’ stool to be more firm and can increase constipation. Currently, only Similac brand formulas do not use palm oil in their ingredients. Similac offers many options, so you can get the protein size you want.

Extra ingredients are… well, extra. This article focused on the main ingredients (protein and carbohydrate) since they impact digestion the most.

However, we’ve all noticed that most formula marketing focuses on all the other sexy, extra ingredients (DHA, MFGM, lactoferrin, HMOs…. to name a few). While these are all nice to have, they are all nonessential extras. And they will not be the deciding factor in whether or not your baby gets into Harvard.

When considering these extras, I suggest parents FIRST focus on finding a protein and carbohydrate blend that keeps their baby comfortable and happy.

Once there, if there is an option with that blend and some sexy extras, and you can easily afford it… go for it! If these sexy ingredients are out of your price range, then do not give them another thought.

Now you know that ingredients should be the number one factor in a formula choice. If you can find your dream ingredients in a store-brand formula… celebrate! That’s what I call shoe money! But let’s be honest, we both know you’ll spend it on diapers.

Similarly, organic ingredients are desirable to many families. However, the ingredients matter more. If full-size proteins cause your infant to be uncomfortable and sleep less, then an organic full-size protein formula is not the best choice for your unique baby. The ingredients are all that matter.

If you are switching formulas, I always recommend going slowly. Over a few days, slowly decrease the amount of old formula in each bottle as you increase the amount of new formula.

This is especially important if the new formula has a larger protein or more lactose. Your baby will have to make more digestive enzymes to digest bigger proteins and more lactose.

Don’t worry — your baby is a rock star — they can totally do that! But giving them a few days to ramp up these enzymes will help the transition go more smoothly.

Most importantly, love your baby and yourself. All babies have gas. All babies fuss. Is your baby loved, fed, and cared for? Then you are doing an amazing job! Be kind to yourself. Trust your intuition… and parent on!


Bridget Young, PhD, CLC, is an assistant professor of pediatrics at the University of Rochester where she studies how variation in breast milk composition and infant formula ingredients impact infant growth and development. As the founder of BabyFormulaExpert.com, she has supported countless families working through formula tolerance issues, helping them find the perfect feeding solution for their baby. You can learn more about working directly with Dr. Young here.