PREGNANCY & CHILDHOOD

A Primer on Protein in Infant Formula

A Primer on Protein in Infant Formula

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Protein plays a role in growth, immune health, and brain development. Here’s what you may want to know.

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SEPT. 12, 2025   4 MINUTE READ
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Human milk is the recommended source of infant nutrition and provides a unique and dynamic mixture of proteins. Infant formulas contain different types of proteins, each with unique characteristics. Depending on the needs of the babies they are designed for, the type and combination of proteins used in infant formulas may vary to support growth.

Read on to learn about the benefits of protein in infant formula, the difference between milk and plant-based proteins, and various formula options based on babies’ needs.

Why do babies need protein?

Protein provides amino acids, which are essential building blocks of protein needed for growth, development, and normal body function. Babies grow rapidly throughout the first year of life and need protein to support normal growth and development. Human milk provides protein in amounts that change over the course of lactation to meet the needs of the growing infant. For babies who do not exclusively receive human milk, infant formulas are carefully designed to provide appropriate amounts of protein to support growth during infancy.1

What kind of protein is used in formula?

Cow’s milk is the protein source most commonly used in routine infant formulas, and it contains two different types of proteins: whey and casein.

Like that of breast milk, our routine cow’s milk-based infant formulas contain a combination of both whey and casein proteins. Additionally, the whey and casein proteins in cow’s milk have different amounts of amino acids than those in breast milk. But infant formulas are specially designed to adjust for those differences, so your baby gets all the essential amino acids they need. Abbott infant formulas include protein blends that have been extensively studied to verify that they support normal growth.

Are some protein sources better than others?

While cow’s milk protein is well-tolerated by most infants, mild tolerance and specialty formulas containing different proteins are available for babies who may benefit from them. The following alternate protein ingredients are available and may be recommended by your pediatrician: 

  • Partially hydrolyzed cow’s milk protein: Formulas like Similac® 360 Total Care Gentle Comfort® where the milk proteins are partially broken down into smaller pieces, making them easy to digest for delicate tummies.
  • Extensively hydrolyzed cow’s milk protein:  Similac® Alimentum® contains protein that’s been extensively broken down into small pieces to virtually eliminate allergic reactions in most babies allergic to cow's milk protein.
  • Soy protein: A plant-based alternative containing protein derived from soy, such as Similac® Soy Isomil®. Soy protein-based infant formulas are options for babies with galactosemia and for families with plant-based preferences.
  • Amino acid-based formulations: Formulas made with free amino acids, rather than intact or hydrolyzed proteins. These are designed for babies with food allergies or GI disorders who cannot tolerate intact or hydrolyzed protein. Your doctor may recommend EleCare® if your little one falls into this category.

All of these formula types provide the necessary nutrients for a baby’s growth and development. Contact your healthcare provider to discuss the best option to feed your baby based on their needs. 

Will a formula with plant-based protein meet my baby’s needs?

The use of formula with plant-based protein is based on personal preference, tolerability, and individual nutrient needs.

All infant formulas in the U.S. – regardless of the protein source – are strictly regulated by the FDA and provide a complete source of nutrition to ensure proper growth and development over the first year of life.

You’ve got this, and we’re here to help

Protein plays a vital role in your baby’s growth, brain development, and immune health.1 While breast milk remains the recommended source of infant nutrition, infant formulas are carefully regulated and formulated to provide the nutrients needed to support normal growth and development when breastfeeding is not possible. Similac offers a range of safe, science-backed formulas—including cow’s milk, hydrolyzed, soy, and amino acid-based options—designed to support digestion, absorption, and healthy growth. Each product is carefully formulated to meet the nutritional needs of different infant populations. Always consult your pediatrician to choose the best feeding option for your baby.

References:

  1. Greer, F. R., & Abrams, S. A. (Eds.). (2025). Protein. In Pediatric Nutrition (9th ed.). American Academy of Pediatrics. 

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