A Formula for Success: The Ultimate Guide to Infant Formulas


Maybe breastfeeding didn’t work out for you. Or maybe it was going well until you went back to work. Maybe you were never really interested. Whatever that case, you’ve decided to feed your baby formula. You don’t have to apologize, feel guilty, or justify your reasons to anyone. While breast milk is the ideal nutrition for infants, we’ve done a pretty good job approximating it–good enough, anyway, to get kids through their first year with excellent nutrition and growth. But while formula feeding may be less stressful than the first few days of breastfeeding, choosing one can be overwhelming.

If you don’t have a baby (yet), or you haven’t had one in a long time, take a walk down the formula aisle next time you’re at the supermarket. It’s astonishing. If you thought nipples were confusing, you’re in for a shock. Formulas come in powders, concentrates, and ready-to-feed bottles. They can be milk-based, soy-based, partially-hydrolyzed, or elemental. There are several major brand names, and every store offers their own store-brand–you don’t want to be the mom who gives her baby store-brand formula…or do you? There are organic and non-GMO options. There are formulas for newborns, young infants, older infants, and toddlers. I think in total, there are 7,341 infant formulas to choose from. (I made that number up, but that’s the way it feels–click here for a list.) The only time I’ve been more overwhelmed by choices is trying to pick out a decent dog food.

Honestly, most of it is just branding and marketing hype, but there are some real differences that you need to be aware of. So here are some answers to common questions. I have also published a detailed list of commercial infant formulas, which is intended to supplement this post.

Regulation of infant formulas

Formulas marketed for use in infants are extensively regulated by the FDA. They’re not approved prior to distribution like medications, but they all have to meet certain minimum requirements. What this means is that, while there are some key differences among formulas (which I’ll get to later), even the store brands provide the nutrients that babies need. Of course, a particular infant may do better on a certain brand-name formula than on a certain store-brand formula–but the same is true for comparing two brand-name formulas. In the end, it comes down to what’s inside the can, not whose name is on the label. Additionally, for most children, there’s no reason you can’t switch formulas because one goes on sale or because your favorite is out of stock. But if you notice that your baby has trouble with a specific formula, avoid that one in the future.

Standard formulas (Enfamil Infant, Gerber Good Start Gentle, Similac Advance)

Let’s start here, if for no other reason than to have a baseline for comparison. The whole point of infant formula is to mimic breast milk as closely as possible–we’ll never get there, but what we have is truly impressive. Standard infant formulas are made from cow’s milk (basically because we have to start somewhere, and cow’s milk is the cheapest and most readily-available source). But because baby cows and baby humans have different nutritional requirements, there are a few key differences. While there are an overwhelming number of formulas available, the majority of infants will do well on a standard infant formula. Here’s a look at what’s in infant formula:

  • Proteins are molecules that form vital components of all cells (not just muscle). Some proteins are structural; others have a specific function. They’re formed from small pieces called amino acids, which are arranged in a specific order dictated by the DNA of the cell that makes them. Dietary proteins are broken down in the gut to short chains called peptides, then into individual amino acids; they are then absorbed by the body and transferred to other cells where they are recycled into new proteins. The two main proteins found in milk are whey and casein (also known as curds–remember Little Miss Muffet?). Breast milk has a ratio of roughly 70% whey to 30% casein–but this varies based on the mother and the infant’s age. Cow’s milk, on the other hand, is only 20% whey and 80% casein. It’s worth noting, however, that the whey and casein found in cow’s milk is not exactly the same as that found in human milk. Because casein forms curds, it tends to remain in the stomach for a little longer, potentially allowing babies to feel full for longer. However, whey protein tends to be easier to digest and leaves the stomach faster, which may reduce the risk of reflux; it may also produce softer, more frequent stools. Most infant formulas are tailored to match the ratio found in breast milk–or to include an even higher percentage of whey.
  • Lipids (also known as fats) are molecules used by the body for a variety of purposes. Many people think of fats as unhealthy, but they are a nutritional necessity. Like proteins, lipids come in a variety of shapes and sizes, and they are broken down and reformed into structures that the body needs. Cholesterol is a major component of breast milk, but can’t be included in formula because it doesn’t remain stable through the commercial production process. Despite this, most infants do just fine making their own. Some specific lipids that you’ll see on formula packages are DHA and ARA. While these lipids–which are also found in breast milk–weren’t added to infant formulas prior to 2001, several studies have shown that they may improve brain development and visual function. They’re not officially recommended or required, but they don’t cause any known problems, and they are now found in almost every commercial formula. MCT oil (medium-chain triglyceride) is another topic that comes up occasionally. It’s used in some children that have problems absorbing fats, but in the majority of children, it’s unnecessary as they are more than capable of breaking these down on their own.
  • Carbohydrates, also known as sugar or starch, are a primary source of energy. Like fats, they have gotten a bad reputation in the world of fad diets. But they are a normal and healthy part of the diet. The carbohydrates found in milk-based formulas are lactose and maltodextrin.
  • Vitamins, minerals, and electrolytes are also required components of infant formulas. They are regulated by the FDA and present in concentrations that provide the required levels of each specific nutrient. One common example is iron, an important nutrient for building red blood cells which wasn’t required until relatively recently. Many formulas still feature “with iron” on the label, but don’t be fooled. They all have it. Vitamin D is another topic that comes up frequently. It’s present in all infant formulas, but often not in a high enough concentration to provide the recommended levels. Talk to your pediatrician about whether a vitamin D supplement is appropriate for your baby. Finally, the electrolytes in formula are present in specific ratios that prevent dehydration or imbalances in the blood that can cause seizures or death. This is the reason why you should always mix formula as directed on the package, unless instructed to do otherwise by your pediatrician.
  • Nucleosides/nucleotides: These are the molecules used by our cells to make DNA and RNA. They can be formed by breaking down and recycling other nutrients, but are found in their free forms in breast milk. They’ve been shown to have some benefits in early growth, and they may help to improve the infant’s immune function. They’ve been added to infant formulas since the 1990’s.
  • Prebiotics and probiotics are substances that promote healthy bacteria. We are all colonized with billions of beneficial bacteria–called microbiota. These bacteria are present in a variety of places, but most notably on our skin and in the gut. Healthy gut flora has been shown to be protective against autoimmune diseases, diarrhea, obesity, and many other disease processes. Prebiotics are substances that stimulate the growth of healthful bacteria. Think of them as microbiota fertilizer (organic, of course). Probiotics are living organisms–the beneficial bacteria themselves. Breastfed infants get many beneficial bacteria from breastfeeding, and adding these substances to formula is an attempt to get the same results. These are not required ingredients in infant formula.

Soy-based formulas (Enfamil ProSobee, Similac Isomil, Good Start Soy)

Instead of the casein and whey proteins found in animal milk, soy formula contains proteins extracted from soybeans. They also don’t contain lactose, a carbohydrate found in cow’s milk. Soy formulas are used for infants with galactosemia, a rare metabolic condition for which avoiding lactose is absolutely necessary. They are also sometimes used in infants thought to have lactose intolerance, although this is very rare in infants. Soy formulas have been used for infants with allergy or intolerance to milk proteins; however, many of these infants will also react poorly to soy, so this is not the ideal formula for them. Another frequent use of soy formulas is by parents who–for whatever reason–prefer that their baby doesn’t receive animal products.

But we’re not feeding baby soybeans, and because soy products are not nutritionally complete for humans, they are supplemented with additional amino acids. There is some evidence that the phytoestrogens in soy products can cause estrogen effects (breast enlargement, etc.) in large enough doses. How much of a factor this plays in infants who drink soy formula hasn’t really been established. In general, unless there’s a good reason to use soy, I’d stick to the cow’s milk-based formulas. But for parents who desire to avoid animal milk, for gassy infants thought to have lactose intolerance, and certainly for those with galactosemia, soy formulas are a reasonable option.

Extensively-hydrolyzed formulas (Enfamil Nutramigen, Gerber Extensive HA, Similac Alimentum)

These are formulas in which the proteins have been broken down into smaller pieces, making them easier to digest and reducing the risk of allergy. While some standard formula will use partially-hydrolyzed proteins, these take it to the next level and are considered to be “hypoallergenic” formulas. For the majority (about 90%) of infants with milk protein intolerance, this is enough to keep the infant from having symptoms. It’s also a less expensive option than elemental formulas, which I’ll discuss next.

Elemental formulas (Neocate, EleCare)

These formulas use proteins that have been completely broken down into individual amino acids. Because there are no intact proteins, they do not cause allergic reactions. They are very expensive, and unless your baby has problems with extensively-hydrolyzed formulas, they may not offer any additional benefit.

Premature infant formulas (Similac NeoSure, Enfamil EnfaCare)

Infants who are born prematurely have a unique set of nutritional requirements. All the growth and development the typically happens in the later part of gestation has to be accomplished after delivery. Depending on how early an infant is born (and what other complications there may have been), infants may be started out on IV nutrition, transitioned to tube feeds, and then work on feeding by mouth over a period of days to weeks. The entire topic of nutrition in the premature infant is beyond the scope of this post, but by the time infants are ready to go home from the NICU, they are often taking one of two formulas: Similac NeoSure of Enfamil EnfaCare. These formulas have a higher calorie content (22 Calories per ounce vs the typical 20). But that’s not the only difference. They also have higher protein, calcium, and phosphorous levels to meet the unique needs of premature infants. Some of the lipids in these formulas is provided in the form of MCT oil, which is easier for the premature gut to handle. Don’t start one of these formulas without your doctor’s recommendation, and don’t switch to another formula without their recommendation.

Formulas for “problems”

Another marketing strategy is targeting parents of children with “problems” like fussiness, gas, reflux, or colic (whatever that is). But unlike formulas for supplementation or different stages, they are actually different and may be helpful for some babies. The difference may be partially hydrolyzed protein, lower lactose, probiotics, rice starch, or other modifications. (See the list below for specifics.) They tend to be more expensive, so unless they’re truly necessary, it may not be worth the extra cost. And if your baby has significant issues, a more significant change may be in order. If you’re concerned that your infant’s symptoms may be caused by her formula, talk to your pediatrician about whether changing formula may be helpful.

Formulas for supplementing

One of the newer marketing strategies from the formula companies is to capitalize on the breastfeeding market by promoting their formulas as being ideal for supplementing. All three major formula makers now have these products. But what’s the difference between a formula designed for supplementing and a standard infant formula?

  • Similac Advance vs. Similac for Supplementation: I compared these formulas side-by-side. The nutrition facts are exactly the same. The website mentions something about prebiotics in the Supplementation version making the infants stools more like breast milk stools. I’m not sure that’s true. And if it is, I’m not sure it’s important. And, by the way, Similac Advance contains prebiotics, too. This appears to be a relabeled product to allow Similac to keep up with the competition.
  • Enfamil Newborn vs. Enfamil for Supplementing: Enfamil for Supplementing has a slightly higher protein/carbohydrate ratio, and lower linoleic acid. It contains slightly more sodium, calcium, and phosphorus. It has a higher vitamin D content that Enfamil Infant, but the same as Enfamil Newborn. Enfamil for Supplementing has a lower lactose concentration, and the majority of the carbohydrates come from corn syrup. I’m not sure how this relates to supplementing.
  • Gerber Good Start Gentle vs. Gerber Good Start Gentle for Supplementing: The supplementing version contains more vitamin D and has probiotics instead of the prebiotics in the standard formula.

Overall, these differences are very minor–almost certainly not enough to justify a seperate product, unless it allows you to compete for a larger market share. It would probably be better if all formulas contained more vitamin D, but if that’s a concern, you can add it yourself. And if the goal of formula is to replicate breast milk, why would infants who are partially breastfeed need a different formula? There’s nothing wrong with these formulas, but don’t fall for the marketing hype.

Formulas for different stages

The theory here is that the goal of infant formula is to replicate breast milk, and breast milk on day 2 is a lot different than it will be 2 weeks–or 9 months–later. In reality, though, the differences are minimal and probably irrelevant–very similar to the supplementation formulas above. Here’s a comparison:

  • Enfamil Newborn vs. Enfamil Infant: The Newborn version has a slightly higher vitamin D content, and a little more linoleic acid. Otherwise, they look identical. The vitamin D is nice. But otherwise, much like the formulas for supplementing, the difference is probably not significant.
  • Similac Advance Stage 1 vs. Stage 2: Stage 1 is marketed for 0-12 months, while Stage 2 is marketed for 6-12 months. The Stage 2 formula has slightly higher protein, calcium, and phosphorus–but by this time, most infants are obtaining nutrition from other sources as well. If you want to switch at 6 months, that’s fine. But don’t be surprised if you don’t see a difference.

Toddler formulas

Perhaps the boldest move by the formula companies is the attempt to double their market by creating “toddler formulas.” These are a relatively new idea, and they appeal to parents who want to provide the best nutrition for their young children–you know, people like you. But there’s no reason toddlers need to be on formula. After their first birthday, they should be obtaining the majority of their nutrition from solid food. And because of that, it’s totally fine to switch to plain-old, buy-it-in-a-gallon-jug milk. Depending on your child’s weight and diet, low-fat milk may be better than whole milk; talk to your pediatrician for specific recommendations. But there’s no reason you need to spend money on toddler formula. Even if you buy organic milk, toddler formula costs about 4 times as much. Not a bad deal for the formula companies. Save your money, or spend it on produce.

Crunchy Organic and non-GMO formulas

For some families, ensuring that their food is organically-grown, sustainably-sourced, and GMO-free is important. Other families don’t value those qualities as much, or don’t have the extra cash to pay the difference. If organic is your thing, that’s great; I certainly don’t have a problem with it. But it’s important to remember that “natural” things aren’t necessarily healthful. More important than how food was produced is what the food is. I’d give my kids conventionally-grown blueberries over organic, non-GMO gummy bears any day.

There are some commercially-available options for organic, GMO-free infant formulas. They cost more than standard formulas, and there’s no evidence that infants fed organic or non-GMO formula will be healthier. Just to put things in perspective–unless a mother consumes only organic food for 12 months prior to her baby’s birth, never takes antibiotics, and spends at least three month per year grazing in a pasture (kidding) her breast milk wouldn’t qualify as “organic,” either. If you don’t care or can’t afford them, don’t feel guilty. But if you value these qualities, and it’s in the budget, go for it.

Formula preparations

As if it weren’t hard enough to choose a formula, many of them come in different preparations as well. But this is really a much easier choice. They’re all equally good; they differ only in cost and convenience.

  • Powdered: This is the most common and least expensive option. Mixing it properly is important, but doesn’t require an advanced degree. Just follow the instructions on the can.
  • Concentrate: This type of formula comes as a concentrated, but still must be mixed with water before feeding. It’s a little bit easier to mix than powdered formula, but it’s also more expensive, and we’re talking seconds. I’m really not sure why they make it.
  • Ready-to-feed: The most convenient option, and also the most expensive. Not a bad option for road trips, hurricane kits (hadn’t thought about that, had you), or other situations when clean water might not be readily available. Otherwise, unless you have trouble mixing things correctly, or you have more money than you can spend, you should probably stick with the powder. (If you have more money than you can spend, let me know. I have some ideas.)

What not to do

In a recent post, I discussed the history of infant formulas–what we’ve learned, and what some of us seem to have forgotten. Using cow’s milk or goat’s milk was a decent option–hundreds of years ago, when the choices were that or nothing. But we’ve come a long way since then, and we know that human and animal milk differ in many ways. Formula is by far the closest approximation to human milk. Trust me–you don’t want to make your own DIY formula at home. And please don’t fool yourself into thinking that because raw goat milk is more “natural,” it’s better for your baby. It’s not.

Also, some parents try to cut down on the cost of formula by diluting it with water. But this practice can result in dangerous electrolyte abnormalities, seizures, and death. (Yes, it can kill your baby.) Unless directed to do otherwise by your baby’s doctor, you should always mix formula according to the package instructions. So, if you’re in a situation where you really can’t afford to feed your baby, ask for help. Talk to your local WIC office or ask your pediatrician where you can turn for help.


For the majority of infants, whether or not the formula is being used to supplement, and whether they are 3 days or 11 months old, a standard infant formula–any standard infant formula–should do the trick. Don’t fall for the marketing hype or pay more when there’s no real difference. And if you’re concerned that your baby has a serious problem, talk to your pediatrician. For a detailed list of available infant formulas, click here.

Leave a Comment