Baby formula is built from three core components: a protein source (usually cow’s milk), a blend of vegetable oils for fat, and a carbohydrate like lactose for energy. From that foundation, manufacturers add vitamins, minerals, fatty acids, and other compounds to approximate the nutritional profile of human breast milk. The FDA requires minimum amounts for 29 specific nutrients and sets maximum limits on 9 of them, so every formula sold in the United States hits a tightly regulated baseline regardless of brand.
The Protein Base
Most standard formulas start with cow’s milk that has been heavily processed to make it digestible for infants. The two main proteins in milk are whey and casein. Human breast milk is whey-dominant, so many formula manufacturers adjust the ratio to bring it closer to breast milk’s balance, often landing around 60:40 or 50:50 whey to casein. Some formulas remain casein-dominant, with ratios closer to 18:82, which is more like unmodified cow’s milk.
For babies who can’t tolerate cow’s milk protein, there are several alternatives. Soy-based formulas replace dairy protein entirely with soy protein isolate. Partially hydrolyzed formulas use cow’s milk protein that has been broken into smaller fragments, making it easier to digest. Extensively hydrolyzed formulas break the protein down even further, into very small peptides. And at the far end of the spectrum, amino acid-based formulas skip intact protein altogether, using individual amino acids as building blocks. These are reserved for babies with severe allergies or feeding intolerances.
Fats and Fatty Acids
Fat makes up roughly 46% of the calories in infant formula, and it comes almost entirely from vegetable and seed oils. The specific blend varies by brand, but common choices include soybean oil, coconut oil, sunflower oil, and safflower oil. Each oil contributes a different mix of fatty acids, and manufacturers combine them to match the fatty acid profile a baby needs for growth and brain development. Some brands intentionally exclude palm olein oil because it has been shown to reduce absorption of certain nutrients, particularly calcium.
Beyond the base oils, most formulas now include two long-chain fatty acids that play a critical role in brain and eye development: DHA and ARA. These are the same fatty acids found naturally in breast milk. In formula, DHA typically comes from algal oil (produced by microalgae) and ARA from fungal oil, both grown in controlled fermentation settings. A typical supplemented formula contains at least 17 mg of DHA and 34 mg of ARA per 100 calories, concentrations designed to mirror what’s found in human milk.
Carbohydrates for Energy
Lactose is the primary carbohydrate in breast milk, and it serves the same role in most standard cow’s milk formulas. It provides about 4 calories per gram and is the main energy source your baby draws from during feeding.
Not all formulas use lactose, though. Soy-based and lactose-free formulas typically rely on maltodextrin, a starch-derived carbohydrate with the same caloric density as lactose. In the European Union, other options like pre-cooked starch and gelatinized starch are also authorized for use in infant and follow-on formulas. Some formulas use corn syrup solids, which function similarly to maltodextrin as a quick source of digestible energy.
Vitamins, Minerals, and Iron
Every infant formula is fortified with a long list of micronutrients: vitamins A, C, D, E, K, and the full range of B vitamins, plus minerals like calcium, phosphorus, zinc, and iron. These are added in precise amounts to meet federal requirements, since the cow’s milk or soy base alone wouldn’t provide everything a baby needs.
Iron is one of the most important additions. Standard iron-fortified formulas contain about 12 mg of iron per liter, which supports healthy blood cell production and brain development during the first year of life. Low-iron formulas were once available but have largely fallen out of favor because pediatric guidelines consistently recommend iron-fortified options.
Prebiotics and Human Milk Oligosaccharides
One of the more recent additions to infant formula is human milk oligosaccharides, or HMOs. Breast milk contains over 150 different HMO structures, which feed beneficial gut bacteria and support immune development. Formula manufacturers can’t replicate that full diversity yet, but two specific HMOs are now commercially available and added to many premium formulas: 2′-fucosyllactose (2′-FL) and lacto-N-neotetraose (LNnT).
These compounds aren’t extracted from human milk. They’re produced through industrial-scale fermentation using genetically engineered bacteria. The process took decades of metabolic engineering research to develop, and it now allows production of these two HMOs in quantities large enough for commercial formula. Many formulas also include other prebiotic fibers like galactooligosaccharides (GOS) or fructooligosaccharides (FOS) to encourage healthy gut bacteria, though these aren’t the same as true HMOs.
Nucleotides
Breast milk naturally contains nucleotides, which are basic building blocks of DNA and RNA. They appear in lower concentrations in unsupplemented formula, so many brands add them back in. Research suggests dietary nucleotides play a role in immune function and in the growth and repair of the gut lining. Clinical studies in infants have linked nucleotide supplementation with improvements in gut microflora, reduced episodes of diarrhea, and better immune response.
Emulsifiers and Stabilizers
If you’ve looked at a formula label and noticed ingredients that seem out of place, like soy lecithin or carrageenan, these are emulsifiers and stabilizers. They’re functional ingredients rather than nutritional ones. Ready-to-feed and concentrated liquid formulas are especially likely to contain lecithin, carrageenan, and mono- and diglycerides, all of which prevent the formula from separating during its shelf life. Powdered formulas generally need fewer of these additives since they’re mixed fresh before each feeding.
How Specialty Formulas Differ
The ingredients above describe standard cow’s milk formula, but specialty formulas make targeted swaps depending on the baby’s needs. Soy formulas replace dairy protein with soy protein isolate and swap lactose for maltodextrin or corn syrup solids. Extensively hydrolyzed formulas keep cow’s milk as the protein source but break it into such small fragments that the immune system is far less likely to react to it.
Amino acid-based formulas represent the most dramatic departure from standard formula. They contain no intact protein at all, only free amino acids. They also tend to be lactose-free and use a higher proportion of medium-chain triglycerides as their fat source, which are easier to absorb. These formulas have a noticeably different nutrient profile: higher osmolarity (meaning the liquid is more concentrated), different mineral levels, and a distinct taste that many babies need time to accept. They’re typically only used when other formulas have failed.
Across all types, the goal is the same: to deliver a complete nutrition source that supports a baby’s growth, brain development, and immune function during the first year of life, using ingredients that are carefully regulated and tested before they reach store shelves.