Every baby formula sold in the United States must contain all the essential nutrients your infant needs in their first year, thanks to strict FDA regulations. However, the biggest differences between formulas lie in the types of proteins, carbohydrates, and fats they contain, plus any additional ingredients designed to mimic breast milk or support your baby's development. Understanding these differences can help you make an informed choice that works best for your individual child.

Feeding a baby comes with a steep learning curve, regardless of whether it's your first child or your fourth. That's because every baby is different—even siblings within the same family—and what works well for one child may not work for another. The same applies when choosing the best infant formula. While the American Academy of Pediatrics (AAP) encourages breastfeeding exclusively for the first six months, it's estimated that 60 percent of infants are not breastfeeding at all by one year of age. In those cases, the AAP recommends using an iron-fortified infant formula as the best and safest alternative to breast milk during a baby's first year.

What's Actually Inside Your Baby's Formula?

Baby formula is designed to serve as an infant's first food, either alongside or in place of breastfeeding. Infant formula is primarily made of macronutrients (carbohydrates, protein, and fat) and micronutrients (vitamins and minerals). It may also contain components found in breast milk, like prebiotics, probiotics, and nucleotides.

As an infant's potential sole food source, all baby formulas must contain three macronutrients that make up at least 98 percent of what's in the can. But the sources and amounts of those nutrients can differ significantly. Here's what you might see on formula labels:

• Carbohydrate Sources: Lactose (the source found in breast milk), corn syrup or corn syrup solids, maltodextrin, glucose, sucrose, or rice starch used as a thickener
• Protein Sources: Milk protein isolate, whey protein concentrate or isolate, soy protein isolate, or casein hydrolysate
• Fat Sources: High oleic oil (usually safflower or sunflower oil), palm oil or palm olein, soybean oil, coconut oil, or canola or rapeseed oil

Why Does the Type of Carbohydrate Matter?

Most experts recommend starting with an infant formula that lists lactose as the first ingredient, which is most similar to breast milk. It's a common misconception that babies can't digest lactose. "Lactose intolerance in adults is common, but incredibly rare in infants," explains Bridget E. Young, PhD, an associate professor of pediatrics at the University of Rochester School of Medicine and Dentistry and founder of babyformulaexpert.com. "Drinking lactose as a baby is part of what makes us mammals!"

However, some infants are allergic to the proteins in cow's milk-based infant formulas, a condition known as cow's milk protein allergy (CMPA). Signs may include excessive crying and fussiness, poor feeding, eczema, loose or watery stools, and in rare cases, blood in stool or anaphylaxis. If your child is diagnosed with CMPA, their healthcare provider may recommend a fully hydrolyzed formula to help with digestion.

Some formulas use corn syrup or corn syrup solids as a primary source of carbohydrates for several reasons. It's inexpensive to produce, which helps keep formula costs down. It's also easy to digest for infants with still-developing digestive systems and serves as an alternative for those who may have conditions or allergies preventing them from consuming breast milk or other formula types. Additionally, it's a very sweet sugar typically used in formulas with broken-down (hydrolyzed) proteins, which may help mask the bitter taste.

It's worth noting that corn syrup and corn syrup solids are not the same as high-fructose corn syrup (HFCS), which has undergone further processing to increase the amount of fructose. No U.S. formulas currently contain HFCS. While corn syrup's use in infant formula has been shown to support infants' growth, recent observational research shows that babies fed formula made with corn syrup may have a higher risk of obesity in the first five years of life. However, this doesn't mean there's a direct link—more research is needed, and numerous factors can contribute to a person's weight and health status beyond diet, such as genetics, environment, socioeconomic status, access to healthcare, and other social determinants of health.

How to Choose the Right Formula for Your Baby

• Start with Your Pediatrician: Your pediatrician is your best resource for specific formula recommendations based on your baby's unique needs and any potential allergies or sensitivities
• Consider Cow's Milk-Based Formulas First: Many parents start formula-feeding with a cow's milk-based infant formula, the most widely available and cost-conscious option, as most babies tolerate them well
• Watch for Digestion Issues: Some families may consider switching to a different protein source if their infant seems to be having trouble digesting their current formula, though this is less common
• Choose Ready-to-Feed for Young Infants: If your baby is under two months of age, was born prematurely, or is immunocompromised, the FDA recommends starting with a ready-to-feed variety that doesn't require adding water
• Switch to Powdered After Two Months: After two months, you can probably switch to powdered formula, which tends to be more budget-friendly while still meeting all nutritional requirements

The best formula for your baby will be one they tolerate well, is safe, fits your budget, and is readily available. Thanks to strict nutrition regulations, any formula sold in the U.S. must contain all the essential nutrients your baby needs in their first year to help them grow. The key is finding the right match for your individual child's needs and your family's circumstances.