May 2024 Issue

Probiotics: Breast Milk Benefits in Infant Formula
By Mindy Hermann, MBA, RDN
Today’s Dietitian
Vol. 26 No. 5 P. 10

Replicating Helpful Bacteria for Greater Nutrition

Within the health care community, there’s little doubt that breast milk, with its ideal balance of proteins, fats, carbohydrates, and beneficial probiotic bacteria strains, is best for babies. Probiotics are “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host,” according to the International Scientific Association of Probiotics and Prebiotics.1 Achieving this nutritional balance is the challenge infant formula manufacturers face.

This article will explore the benefits of probiotics for young infants, discuss the current probiotic formula marketplace, and provide guidance on how RDs can help parents and caregivers meet their infant’s needs.

Probiotic Benefits in Infants
Young infants can experience the benefits of probiotics from the start. Human breast milk contains diverse beneficial microbial communities that help colonize the gut and play a role in the development of the immune system and protection of the gastrointestinal tract from pathogens.2 More than 200 bacterial strains have been identified, including important strains of Lactobacilli, Bacteroides, and Bifidobacterium.3

Anna Busenburg, RD, CSP, LD, CLC, registered dietitian II, in the division of neonatology—nutrition therapy at Cincinnati Children’s Hospital Medical Center, says that while Bifidobacterium and Lactobacillus have potential probiotic roles, “How these bacteria colonize infants are almost as numerous as the number of strains. Bacterial presence starts to occur as early as prenatally during the third trimester and is influenced by birth method, maternal health, method of feeding for the infant, maternal nutrient intake, geographic area of the maternal baby dyad, and many other factors.”

The gut colonization process is thought to last until the child is about 3 years old. The digestive tract of breastfed infants tends to have more beneficial bifidobacterial strains and fewer strains of clostridium, enterococcus, klebsiella, and enterobacter.4,5 In contrast, the microbiome of formula-fed children tends to resemble the digestive tract of adults. Breast milk also contains prebiotic human milk oligosaccharides (HMOs) that are metabolized by bifidobacteria into acetic acid and short-chain fatty acids and can help inhibit the growth of pathogenic bacteria.

Manufacturers Replicating Breast Milk
In an effort to replicate the contents of breast milk in infant formula, manufacturers initially added probiotics to their formula products. However, given the complexity of breast milk, they questioned whether adding probiotics could offer similar health benefits as breast milk. In one study, researchers divided infants into three feeding groups: breast milk, probiotic formula, or placebo formula with no added probiotics.6 The probiotics—L. rhamnosus GG, Lactobacillus fermentum LC40, Lactobacillus reuteri DSM 17938, and B. lactis BB-12—were selected based on their acid, bile tolerance, and safety assays. Compared with placebo, the probiotic formula improved stool consistency and defecation frequency, helped maintain the level of secretory immunoglobulin A, decreased stool acidity, increased concentration of the short-chain fatty acid butyrate, and increased colonization by health-promoting bacteria.

“With all the bacterial components found in human milk and in infant stool, the research shows that these organisms can have a positive impact on overall growth, tolerance of feedings, and ease of digestion,” Busenberg says. “However, the challenge has been identifying all the components of human milk and then understanding how they can be replicated and added to commercially available formula. Identifying other components in human milk, including proteins, fats, and human milk oligosaccharides, is part of this story.”

Importance of Prebiotics and Probiotics
Incorporating prebiotics is another important component. Prebiotics have been defined as “substrates that are selectively utilized by host microorganisms conferring a health benefit.”7 Prebiotic milk oligosaccharides in breast milk are the third most abundant solid component after lactose and lipids. These indigestible carbohydrates nourish probiotic bacterial strains in the gastrointestinal tract,4 and more than a dozen HMOs have been identified to date.

Beneficial microbes supported by HMOs, including Bifidobacterium infantis, bifidum, breve, and longum, help promote infant health. HMOs are metabolized by intestinal microorganisms to produce short-chain fatty acids, which are crucial for infant development and also appear to reduce risk of illness from gut pathogens.3

Formulas sold in Europe and Asia tend to be ahead of the United States regarding their addition of probiotic strains and prebiotic HMOs. Regional Chinese brands choose from several probiotic strains, including Bifidobacterium animalis BB-12 and Bifidobacterium animalis subsp. lactis HN019, Bi-07, and BB-12. Some formulas also contain up to six added HMOs. In Europe, for example, Aptamil is supplemented with prebiotic galacto-oligosaccharides, fructo-oligosaccharides, and probiotic Bifidobacterium breve M-16v, while Nestlé Beba Supreme includes a complex of six prebiotic oligosaccharides modeled from breastmilk—2’-Fucosyllactose, 3’-Fucosyllactose, lacto-N-neotetraose, difucosyllactose, 3’-Sialyllactose, and 6’-Sialyllactose, along with the lactic acid cultures Bifidobacterium longum subsp. infantis and Bifidobacterium lactis.

Leading US Formulas With Probiotics
“The two most common bacterial strains in US formulas are Bifidobacterium and lactobacillus,” says Krystyn Parks, MS, RD, IBCLC, owner of Feeding Made Easy, LLC, in Lake Forest, California. “I’ve seen staphylococcus and streptococcus strains as well, particularly in supplements. Most of the benefit claims relate to populating the gut with “good” bacteria, but research is looking into probiotics for eczema, immune response, and colic as well,” adding that probiotics may be present only in powdered formulas since liquid, ready-to-feed formulas must be sterile.

Parks says individual formula companies use their own unique strains. “International formulas introduced into the US marketplace during the formula shortage use various Bifidobacterium strains, so we’ve seen an increase in the number of formulas with [these strains]. Previously, more formulas in the US had lactobacillus.” She also says formulas have unique marketing messages.

Busenburg says formula companies ascribe various claims to their probiotic ingredients, including Lactobacillus rhamnosus GG to strengthen the intestinal barrier and support gut health, Bifidobacterium lactis to support a healthy digestive tract, and Lactobacillus reuteri to reduce colic and spitups. They also associate specific prebiotics with benefits, such as Polydextrose + GOS for gut health and softer stools, a prebiotic HMO blend that’s identical to breastmilk, and 2’-Fucosyllactose HMO to strengthen the immune system.

Click to enlarge

Guidance to Parents
Parents and caregivers should work with their infant’s care team to identify the most appropriate formula. Busenberg cautions that “no single product has all the probiotics and prebiotics, and more research is needed.”

“Many formulas don’t contain probiotics, but parents shouldn’t add in a probiotic supplement themselves,” Park says. “A lot of parents start their baby on probiotics without speaking to a doctor. The research is relatively new, and pediatricians don’t yet have blanket recommendations for probiotic use.”

A recent study by the Breastmilk Ecology: Genesis of Infant Nutrition Working Group 2 concludes that human milk’s complex composition and structural matrix comprises “literally thousands of molecules and cell types—many of which likely function independently and interactively to nourish, protect, and communicate complex information to infants, thereby impacting lifelong health.”8 That’s a tough benefits package to replicate.

— Mindy Hermann, MBA, RDN, is a food and nutrition communicator based in metro New York. She’s a consultant for Innova Market Insights, which maintains a database of new global food and beverage product launches, including infant formula.


1. Probiotics. International Scientific Association of Probiotics and Prebiotics website.

2. Kim SY, Yi DY. Components of human breast milk: from macronutrient to microbiome and microRNA. Clin Exp Pediatr. 2020;63(8):301-309.

3. Łubiech K, Twarużek M. Lactobacillus bacteria in breast milk. Nutrients. 2020;12(12):3783.

4. Wiciński M, Sawicka E, Gębalski J, Kubiak K, Malinowski B. Human milk oligosaccharides: health benefits, potential applications in infant formulas, and pharmacology. Nutrients. 2020;12(1):266.

5. Wang K, Xia X, Sun L, et al Microbial diversity and correlation between breast milk and the infant gut. Foods. 2023;12(9):1740.

6. Eor JY, Lee CS, Moon SH, et al. Effect of probiotic-fortified infant formula on infant gut health and microbiota modulation. Food Sci Anim Resour. 2023;43(4):659-673.

7. Prebiotics. International Scientific Association of Probiotics and Prebiotics website.

8. Smilowitz JT, Allen LH, Dallas DC, et al. Ecologies, synergies, and biological systems shaping human milk composition-a report from "Breastmilk Ecology: Genesis of Infant Nutrition (BEGIN)" Working Group 2. Am J Clin Nutr. 2023;117 Suppl 1(Suppl 1):S28-S42.