Which formula is best for the breastfed baby?



Being pro breastfeeding does not mean being anti formula. As an IBCLC lactation consultant, my job actually includes education on safely preparing, handling and feeding infant formula. This includes helping families choose an infant formula that is right for them based on solid evidence based research. If there was more education and less demonizing of formula, families would feel less guilt and stigma around just trying to feed their babies. 

So let’s break down how to choose an infant formula. Here’s the disclaimer: what works for one baby won’t work for all babies. So always speak with your pediatrician or personal health care provider if your baby is struggling to tolerate any infant formula you are using. 

There are three main ingredients that are essential and needed in all infant formulas. The carbohydrate, or sugar source, the protein and the fat. In this video we will just be concentrating on the carbohydrate. Carbohydrates are an important source of energy for growing babies, as they account for 35 to 42% of their daily energy or caloric intake. The number one sugar or carb in breastmilk is lactose. Lactose is not only a good source of energy, it also aids in the absorption of the minerals magnesium, calcium, zinc and iron. It’s also lowest on the glycemic index scale – meaning that it won’t increase blood sugar levels nearly as fast as glucose or sugar will. Lactose is healthier for babies to metabolize, and can help maintain stable blood sugar (and therefore insulin) levels. All human babies have an enzyme called lactase which breaks down the lactose and make sit easily digestible. After about 5 years of age, most people (about 75% of the world's population) stop producing the lactase enzyme. Without lactase, they can no longer digest milk, and they become lactose intolerant. This is actually the age of biological weaning, as in if children were left to self wean, they would do so some time between 2.5-7 years old, meaning the weaning age coincides with no longer being able to break down the sugar. Because of this it is EXTREMELY RARE for a human baby to be lactose intolerant. That disorder is called galactosemia and is an inherited genetic condition This hereditary condition is passed from parent to child as an autosomal recessive disease. This means that a child needs to inherit two copies of the defective gene (one from each parent) in order to have the disease and occurs in only 1 of every 30-40K babies born. 

To replicate the sugar in breast milk, most cow's milk-based formulas will also have lactose as the main source of carbohydrates. When possible, I typically recommend a lactose based formula for most babies because most of the time if an infant is having a reaction to a formula, they are reacting to the protein and not the sugar source. More on protein in a different blog/video. But more on carbs. 

So again, I typically recommend looking for a lactose based formula first. Human babies are designed to break down lactose and it is the most easily digested by the human gut. If you are using a lactose based formula and baby doesn’t seem to be tolerating it, consider a lactose based formula with an alternative protein source first before going to a lactose free formula. 

Because formulas without lactose will use other sources of carbohydrates. Both the FDA and the European Commission require that infant formulas provide 40% of their calories from carbohydrates. However, the source of those carbs is up to the manufacturer of the formula. In the US, carbs can come from five main sources: Lactose, Maltodextrin, Glucose, Sugar, or Corn syrup. Not all of these sugars are created equal! 

Glucose and corn syrup are the sugar source in over half of the formulas produced in the USA. WHY? Because they’re widely available and very cheap to produce. The problem with corn syrup (and all glucose/sugar in general) is that it’s a fast-acting carbohydrate. This means that it’s high on the glycemic index, and quickly increases blood sugar. The EU has some limits and guidance on how much corn syrup can be used, and bans the use of corn syrup solids in organic baby formula, but the US does not. Which means that infant formula in the US can contain 100% of its carb source from corn syrup! Now before you get all fired up, corn syrup is NOT the same as high fructose corn syrup, which is what we are told as adults we need to stay away from. High-fructose corn syrup is corn syrup that has been further treated with enzymes to break down some of the glucose into another common sugar, fructose to make foods taste sweeter. Infant formulas are nutritionally complete and need a source of carbohydrate to provide energy. 

Maltodextrin is a type of sugar that is made up of glucose. Maltodextrin will become syrup if it is broken down further, so it’s essentially the same thing as added sugar.

Glucose syrup is the same thing as corn syrup! It just means that the syrup was extracted from a different plant – but it’s still the same as sugar.Sucrose is table sugar, and has a lower glycemic index than glucose, but higher than lactose.

Corn syrup, sucrose, maltodextrin are most used in “sensitive” formulas. That’s due to the fact that these formulas are designed for babies who are lactose intolerant, and so formula manufacturers are trying to replace lactose with an alternative carbohydrate.

Sometimes some corn syrup or glucose syrup is necessary in hypoallergenic formulas, because those formulas use hydrolyzed milk proteins, which are essentially partially digested milk proteins – and they taste/smell bad! So the corn syrup is used to try to mask the taste of the hydrolyzed milk protein.

But there are hypoallergenic formulas that do not overuse glucose and use healthier forms of carbs. 

There are a few reasons why formula manufacturers choose corn syrup over lactose in baby formula:

  • It’s a carbohydrate that babies can digest
  • It’s cheap to produce
  • Some sugars like maltodextrin also provide the function of thickening and emulsifying the formula for a better “mouth feel”
  • Corn syrup is sweet! And babies like sweet things – which might make formula more palatable to babies.
  • In hypoallergenic formulas, corn syrup might be used to make the formula taste better and mask the hydrolyzed milk protein taste.

So to recap, when choosing a baby formula, lactose is the preferred sugar or carb source for human babies. Prior to switching to a lactose free version, which will have the sugar source coming from another carb product, we should be switching to a formula with lactose with a different protein source which we will be discussing next. 

Formulas: Protein source 

Infant formulas come in powder, liquid concentrate, and ready-to-feed forms. They are designed to be prepared by the parent or caregiver in small batches and fed to baby, usually with either a cup or a bottle. 

There are an overwhelming number of infant formulas on the market and it can be difficult to determine which one is best to give to your baby. As an IBCLC lactation consultant, my job actually includes education on safely preparing, handling and feeding infant formula. Which includes helping families choose an infant formula that is right for them based on solid evidence based research. If there was more education and less demonizing of formula, families would feel less guilt and stigma around just trying to feed their babies while also feeling supported in the medical and nutritional care of their babies. 

So let’s break down how to choose an infant formula. Here’s the disclaimer: what works for one baby won’t work for all babies. So always speak with your pediatrician or personal health care provider if your baby is struggling to tolerate any infant formula you are using. 

There are three main ingredients that are essential and needed in all infant formulas. The carbohydrate, or sugar source, the protein and the fat. In this video we will be talking about the protein source. In my experience, if an infant is going to have difficulty tolerating an infant formula, it’s usually the protein piece that they are struggling to digest and changes to the formula can make a drastic difference in baby’s gut. 

So what is protein? Protein is the building block of all things. Excluding water and fat, the human body is made up almost entirely of protein. Protein is the main component of muscles, bones, organs, skin, and nails. For example, your muscles are composed of about 80% protein. There are at least 10,000 different proteins that make up and maintain different functions throughout your body. Protein is made from over 20 different basic building blocks called amino acids. Because we don’t store amino acids, our bodies make them in two different ways: either from scratch within our own cells, or by modifying others from the foods that we consume. There are 9 amino acids—histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine—known as the essential amino acids, which we can only get for our bodies from the food that we eat. The body breaks down consumed protein into these amino acids, and absorbs it for use. It is used to build muscles and organs, to make hormones and antibodies, to be stored as fat, and to be burned as energy. 

Human milk is made up of protein from the foods we consume and is designed for feeding human babies. When you eat your food, proteins and nutrients go from your mouth to your stomach where they are broken down and passed to your intestine. These nutrients are absorbed in your intestines to your blood stream where it goes to the back of your breast to little sack like cells called alveoli. The alveoli pull nutrients, including protein, from your blood as well as water and milk is made. This milk then goes to your baby’s mouth, their stomach to be broken down and then absorbed in their intestines for their body to use.  Baby’s intensities have human protein receptors to accept and use the protein from human milk, which makes it easily digestible for baby. Protein levels in human breast milk are constantly changing based on the stage of lactation, frequency of nursing, and other biological factors of the mother. Human milk protein concentration, how much protein is in each ounce, is not affected by maternal diet, but increases with maternal body weight for height, and decreases in those producing higher amounts of milk. 

There are actually many types of proteins in human milk, but can be generally divided into two kinds of protein classes: whey and casein. These two kinds can also be further subdivided by a remarkable array of multiple other specific proteins and peptides. So protein is like saying letters, numbers or colors. It’s a general category that can be further broken down into many types of proteins. 

Whey and casein are two different classes of protein found in both breast milk and cow’s milk, as well as the milk of any other mammals. What are whey and casein? Have you heard the nursery rhyme about little miss muffet who sat on her tuffet eating her curds and whey? The curds are the casein and the whey is the liquid. The ratio of curds to whey, as well as then adding additional ingredients, is how we make dairy products like cheese and butter.  This is why they’re the protein sources in routine infant formulas. As we explore these two protein types, there’s one key concept to keep in mind: although both human and cow’s milk contain whey and casein protein, the actual whey and casein proteins in each type of milk are significantly different. In human milk, the ratio between whey and casein is dynamic, and it shifts throughout the course of lactation. In the very early days of milk production, breast milk will have more whey than casein, with a whey:casein ratio of 80:20. After the first few weeks of life, the concentration of whey declines and casein increases until the proteins reach the concentration seen in “mature” breast milk with roughly equal amounts of each protein type, about 60% whey and 40% casein. On the other hand, casein is the dominant protein in cow’s milk, contributing roughly 80% of the protein, while whey makes up about 20%. These differences in proportions relate to different developmental needs of human and cow newborns. Whey proteins are easier to digest, and as a result, provide a more rapid source of amino acids. In contrast, the unique structure of casein proteins—called the casein micelle—makes them harder to break apart and requires a longer digestion time. Such gut muscle activity is referred to as gut motility and its rate is measured as gastrointestinal transit time. Baby cows digest differently than baby humans as a species. Cows’ milk and its proteins are known to delay gastrointestinal transit time. In some people, this may manifest as constipation. In others, delayed transit time in the gut may allow more time for fermentation of fermentable carbohydrates and which leads to intestinal fluid resorption, resulting in softer stools. This is what makes the gassiness and constipation symptoms in babies when consuming milks other than human breast milk. There is much discussion on the digestibility of whey vs. casein. Overall, whey remains a liquid during the course of digestion, while casein forms curds or clots. The pH (or acid level) of the stomach influences how these different proteins behave in the GI tract. The high proportion of casein in unmodified cow’s milk is one of the reasons why regular milk is not an appropriate to feed to young babies. Even after birth, the GI tract still has a lot of maturing to do, and a feeding that provides primarily casein can cause issues for many babies. While it makes some sense for infant formulas to mimic the whey and casein ratio of breast milk, protein is more complex than just ratios! The finer details of the composition of different types of whey and casein, as well as how they function in the body, are also considered when infant formulas are designed. Both whey and casein are considered high-quality proteins and provide all nine essential amino acids we know are required to support growth and development.

Now let’s jump in to the nitty gritty of the different kinds of proteins found in infant formulas so you understand what to look for when you’re staring at the ingredient list on the side of the can. There are many sources of protein used in baby formulas. Animal-based (dairy-based) sources of protein used in baby formulas include cow’s milk, goat’s milk, whey protein, organic milk protein concentrate, milk protein isolate, and casein hydrolysate. Plant-based sources of protein used in baby formulas include soy protein, pea protein, and some times almond butter protein

  • Cow's milk formula is the most commonly used type. An alternative to cow protein would be goat milk protein. 
  • Soy protein based formulas are frequently used for infants allergic to cow's milk or lactose and for those who are avoiding animal products like vegetarians or vegans. 
  • Protein hydrolysate formulas contain protein that's been broken down into smaller sizes than are those in cow's milk and soy-based formulas. Protein hydrolysate formulas are meant for babies who do not tolerate cow's milk or soy-based formulas.
  • Specialized formulas are also available for premature infants and those with specific medical conditions where the protein has been broken down even further. 

Those are the options for protein sources, but let’s break it further down to understand those food labels better. Also, research has shown that baby formulas with high casein may be more difficult to digest. For this reason, baby formula manufacturers often add whey protein, resulting in an adapted whey to casein ratio. Adding whey protein to baby formula may help to reduce tummy troubles in little ones. Remember the whey remains a liquid while digesting but the casein protein stays a solid and is harder to digest. A formula with at least 50, ideally 60% whey is ideal. Each manufacturer determines for their own brand this ratio but the trick thing is they don’t have to list the ratio. Some manufacturers will only list the ratio it there is 100% whey with no casein, (like Gerber Gentle Soothe Pro or Burt’s Bees Ultra Gentle). Most of the time you’ll have to call the manufacturer how much their particular ratio is or you can sometimes deduce how much is in there based on the position of “whey protein” in the ingredients list. For more whey in the ratio, you want it in the top 3-4 ingredients of the list on the label. Now if your baby is already drinking formula and they are tolerating it well, I will always say there is no one size fits all approach to feeding. If your baby seems to be drinking their formula fine with no digestion upsets, meaning constipation or fermented gas, if it ain’t broke, don’t fix it. But if you feel like your baby is struggling in their current formula, this is the ingredient to change first. So when we’re talking about picking formula by protein, first we want to look at the percentage of whey to casein. We usually want 50-60% of whey or possibly more depending on your baby. 

Now let’s break down the casein portion. There are subtypes of casein called “beta-casein” proteins there are a couple of different types, but we will focus on this. It comes in a 1 beta-casein or a  2 beat-casein formula. This is A1 versus A2 beta-casein formulas. The majority of mammal milks, including human milk, produce predominantly or exclusively A2 beta casein. That’s what we as humans are designed to digest. But the majority of our cows in the US produce both A1 and A2 beta proteins. Because we as humans weren’t really designed to digest A1 beta casein, some times we see digestive issues with both adults and babies. Sometimes we see symptoms that are less severe than a true milk allergy but are indicative of a milk protein sensitivity. These babies may benefit from an A2 formula that doesn’t have these beta-casein proteins. These symptoms can include eczema, raspiness, congested-sounding breathing, occasional mucous in the stools, and digestive discomfort. But without the extreme symptoms that we see with CMPA, like widespread rash, projectile vomiting, blood in the stool, poor growth or weight gain and feeding aversion or refusal. So if your baby has trouble with milk protein but testing negative in their stool test for milk allergy, switching to an A2 formula can be a good place to start before jumping to a hypoallergenic milk if there’s no diagnosed CMPA. 

Another option for a gentle formula is to pay attention to whether or not your formula is hydrolyzed. This means they have taken the intact milk proteins and broken them down into smaller pieces which can be easier to digest and have a lesser risk of an allergenic response. A partially hydrolyzed formula means they have some of their proteins broken down. A hypoallergenic formula means it has been extensively hydrolyzed where above 90% of the proteins are significantly broken down. 

Some babies may need an elemental or amino acid formula where there’s no detectable protein at all but instead the amino acid components of protein so there is no protein to react to. Unfortunately many pediatricians will jump to this type of formula when baby is reacting to other formulas instead of systematically working through other formula options first. If you read my other blog on the carbohydrate, one of the biggest concerns with the hydrolyzed and elemental formulas is the sugar source. They are most often using sugars other than lactose, which is the number one sugar in breast milk, to mask the flavor of these formulas. For more information on that see my other video. 

So here’s the summary:

IF your baby is having trouble with their formula, I suggest the following order to try to find a more digestible formula, unless there is obvious evidence there is an allergy:

  1. A formula with more whey protein in the ratio
  2. A formula with A2 protein (even better if it’s an A2 with added whey
  3. A formula that’s partially hydrolyzed (but remember you’re often sacrificing the lactose)
  4. An extensively hydrolyzed formula
  5. An elemental formula 

The other protein options for infant formulas are those the are plant based. Eating plants in the form of fruits and vegetables is good for babies (when they are developmentally read for them of course!). However, there is no nutritional advantage to plant-based infant formulas. For many health care providers, the use of soy-based formulas is often recommended for only those infants who cannot not have dairy-based products because of health, cultural or religious reasons, such as a vegan lifestyle or due to galactosemia. Soy formula is made from soy protein isolate, a product that comes from whole soybeans that have had fat removed (defatted). However, plant based protein is nutritionally deficient compared to animal based protein formula sources as soy is an incomplete protein, which has been a concern with soy formulas. Since infant formula is the only source of nutrition for many babies, it must contain all the nutrients that infants need to grow and thrive. So current soy formulas have added 3 amino acids which are naturally deficient in soy protein including methionine, taurine, and carnitine. 

The other concern with soy protein based infant formulas used to be higher amounts of aluminum found in soy, up to 50% more aluminum in soy than human breast milk. However, 95% of the ingested aluminum is not absorbed in the gut, and the kidney excretes the absorbed 5%, so there are no differences in plasma aluminum levels in children fed with different formulas  

Two potential issues remain for the use of soy formulas: One is the concern about possible hormonal effects on the reproductive system caused by phytoestrogens found in soy protein. Although at present there is no definitive evidence that phytoestrogens have toxic effects in human babies who are fed soy formula, concern has been raised from research carried out in vitro and in animal studies. Phytoestrogens are plant-derived substances with estrogenic activity. There is concern that these isoflavones may mimic the actions of estradiol or alter estradiol metabolism, and consequently modify the processes influenced by estradiol in the body. Estradiol is the primary form of estrogen found in the body during reproductive years that plays a significant role in initiating and maintaining postpubescent female secondary sex characteristics including breast development, changes in body shape, and affecting bones and fat deposition. Despite this theoretical possibility, practical experience has shown that the millions of babies who have consumed these products since the 1960s appear to have grown and matured as expected. Although no overt toxicity is associated with the consumption of soy-based formula in healthy babies, clinical research has shown that babies with congenital hypothyroidism should be cautious when consuming soy based formulas and have their thyroxine levels routinely monitored. 

A recent retrospective human study showed that adults who consumed soy-based formulas as babies showed no difference in rates of reproductive maturity, cancer development and general health as adults who had been fed cow’s milk-based formulas. Additionally, soy formulas appear to be safe from a neurodevelopmental perspective, as shown in a nationwide study of infants born in Korea. Soy formula intake did not increase the risk for developing epilepsy, attention-deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD), or decreased developmental status. Currently available soy-based formulas support normal growth and nutritional status for the first year of life, with no overt toxicities observed in healthy babies. However, soy-based infant formulas may not adequately promote growth in babies who were born premature, and it is not recommended for these babies. 

The other problem to take into consideration is the use of transgenic soy in formulas. The US Department of Agriculture records that up to 93% of soybean crops are transgenic. Due to these nutritional disadvantages, higher allergenicity and less tolerance, the European Academy of Allergy and Clinical Immunology (EAACI) and the European Society for Paediatric Gastroenterology Hepatology and Nutrition (ESPGHAN) recommend not giving soy to babies with CMPA during the first 6 months of life or to children who have experienced gastrointestinal symptoms like constipation or foul smelling gas. Rarely, a soy-based formula is necessary to treat a metabolic disease. In this case, formula is used as a clinical intervention, much like medicine is used. These are exceptional cases and parents are encouraged to follow recommendations of their medical team.

Some families turn to soy-based formulas because of suspected cow’s milk protein allergy. Soy proteins can cross react with cow’s milk proteins; therefore, soy is not an appropriate formula for infants with a cow’s milk allergy. In fact, up to one half of infants with a cow’s milk allergy who are fed a soy formula are also sensitive or allergic to soy proteins (this is called cross reactivity). Both the American Academy of Pediatrics and the European Society for Paediatric Gastroenterology Hepatology and Nutrition (ESPGHAN) Committee on Nutrition recently produced papers on soy protein infant formulas (38,49). They recommend extensively hydrolyzed protein (or amino acid-based formulas if hydrolyzed formulas not tolerated) for the treatment of infants with CMPA. A 2020 review article from Europe recommends avoiding soy formula for infants with cow’s milk allergy who are under 6 months of age. (Concerns for the use of soy-based formulas in infant nutrition. Paediatr Child Health. 2009 Feb;14(2):109-18. PMID: 19436562; PMCID: PMC2661347.)

Rice is one of the less allergenic foods, reacting in less than 1% of allergic children. It has no lactose and no phytoestrogens. For this reason, hypo-allergenic formulae that uses hydrolyzed rice proteins have been developed as another plant based protein alternative for infant formulas. These formulae have now been in use for more than a decade in several westernized countries. Rice protein composition is naturally different from cow proteins: although they are rich in essential amino acids, three of these do not reach the respective value contained in breastmilk.

For this reason, to guarantee nutritional safety to infants allergic to cows milk or soy, partially hydrolyzed rice proteins formulas (HRF) are supplemented with multiple amino acids as several key nutrients like, iron and zinc. Although several studies have shown the hydrolyzed rice protein formulas to be nutritional and allergy safe, they are still recommended as a second choice to elemental or amino acid formulas. 

The BEST formula for you is the one that works best for your baby. This is NOT one size fits all and what works for your baby may not work for other babies. As always, please consult with your child’s health care provider or pediatrician for questions and concerns about your baby’s nutrition growth, and digestive system. This is not medical advice, this is the most current education on the choices available to you and how to interpret the labels on the containers of infant formula.  Manufacturers do not have to disclose their whey to casein ratio on the side of the can, but remember: human milk has a higher whey to casein ratio. If your baby is struggling with a whey based formula, switching to one with a higher amount of whey may help baby digest the formula quicker resulting in less constipation or fermenting gas. 

  • Breast milk has 400+ different proteins.
  • These proteins fit in two categories: i) casein and ii) whey.
  • Protein itself is a nutrient, but also helps absorb other nutrients.
  • Proteins also have antimicrobial and immune-supporting functions.
  • Amino acids are the building blocks of proteins, and each has a unique combination.
  • Therefore, the amino acid profile of whey and casein proteins are distinct.
  • From colostrum to mature milk, the ratio and amounts of whey/casein protein changes.
  • Between the two, whey protein is predominant. It makes up 50-80% of protein content in breast milk.
  • Suffice to say that the protein composition of breast milk is dynamic!
  • Nucleotides are also found in breast milk. They are the building blocks of our DNA.
  • Nucleotides are conditionally essential nutrients during the early stages of life.
  • In infants, they help the immune system and the gastrointestinal tract.