Scientists studied whether adding special bacteria found in breast milk to infant formula could help babies’ digestive systems develop better. They tested two different groups of bacteria with different properties in young piglets—some fed formula with bacteria, some with regular formula, and some with natural mother’s milk. After 24 days, they found that the bacteria from breast milk changed how the babies’ guts worked and which bacteria lived in their stomachs. The bacteria seemed to help the immune system and digestive health, but different types of bacteria had different effects. This research suggests that the specific bacteria in breast milk might be important for helping babies’ guts develop properly.
The Quick Take
- What they studied: Whether adding bacteria naturally found in breast milk to infant formula could improve how babies’ digestive systems and immune systems develop
- Who participated: Young piglets (which have similar digestive systems to human babies) were divided into groups: some received regular formula, some received formula with two different types of breast milk bacteria, and some received natural mother’s milk as a control group
- Key finding: The two types of breast milk bacteria affected the babies’ gut health differently. One type seemed better at boosting immune responses, while both types changed which bacteria lived in the digestive system compared to regular formula
- What it means for you: This research suggests that not all bacteria in breast milk are the same—some may be better at supporting baby health than others. If confirmed in human babies, formula makers might be able to add specific beneficial bacteria to formula to make it more similar to breast milk. However, this is early research in animals, not yet proven in human infants
The Research Details
Scientists created two special mixtures of bacteria that naturally live in breast milk. They chose bacteria based on how well they worked in lab tests—one mixture was designed to reduce inflammation, and the other to boost immune responses. They then fed these bacteria mixtures to young piglets in their formula and watched what happened over 24 days. They collected samples from the piglets’ digestive systems and blood at different time points to measure changes in bacteria types, immune markers, and gut health. The piglets receiving formula with bacteria were compared to piglets getting regular formula and piglets nursing from their mothers (the gold standard for comparison).
This type of study is important because piglets have digestive systems very similar to human babies, making them good models for understanding how infant nutrition works. The researchers measured many different things—the types of bacteria present, immune system markers, and genes involved in inflammation and immune function—to get a complete picture of how the bacteria affected the babies’ health.
The study used advanced laboratory techniques to identify bacteria and measure immune responses, ensuring the findings were based on solid scientific evidence rather than just observation.
Understanding which bacteria in breast milk are actually helpful is crucial because breast milk is considered the gold standard for infant nutrition. If scientists can identify the specific beneficial bacteria and their properties, formula makers could potentially improve infant formula to better match breast milk’s benefits. This is especially important for babies who cannot be breastfed. The research also helps us understand how early nutrition shapes the developing immune system and digestive health.
This study was conducted by experienced researchers using rigorous scientific methods and published in a peer-reviewed scientific journal. The use of animal models (piglets) allows for controlled experiments that would be difficult or unethical to perform in human infants. However, results in animals don’t always translate directly to humans, so human studies would be needed to confirm these findings. The researchers measured multiple outcomes rather than just one, which strengthens confidence in the results. The study included appropriate control groups for comparison, which is essential for drawing reliable conclusions.
What the Results Show
The two different bacterial mixtures had distinct effects on the piglets’ digestive systems. The bacteria changed which types of microorganisms lived in the gut—particularly affecting bacteria belonging to a large group called Bacillota. These changes were visible both early (day 8) and later (day 24) in the study.
When it came to immune function, the bacteria mixtures activated different immune pathways. Both types of bacteria increased activity in genes related to immune regulation and antioxidant protection (the body’s natural defense against damage). The mixture designed to boost immune responses (HI) was particularly effective at increasing a protective immune protein called secretory IgA, which helps defend the digestive tract.
Interestingly, the bacteria added to the formula actually influenced which natural bacteria grew in the piglets’ guts, suggesting the added bacteria weren’t just passing through—they were actually changing the environment and helping beneficial bacteria thrive. The piglets receiving the bacteria-supplemented formula showed patterns more similar to piglets nursing from mothers than to piglets receiving plain formula.
The study found that the bacteria also affected the piglets’ blood immune cells. When researchers stimulated blood cells from piglets that received the immune-boosting bacterial mixture, these cells produced more immune signaling molecules (cytokines) compared to cells from piglets receiving plain formula. This suggests the bacteria influenced not just gut immunity but also the body’s overall immune system. Additionally, the researchers found correlations between the added bacteria, the natural bacteria that grew in response, and various measures of gut health, suggesting these elements work together as a system rather than in isolation.
Previous research has shown that breast milk contains bacteria and that these bacteria influence infant gut health, but exactly which bacteria matter and how they work has been unclear. This study advances that knowledge by testing specific bacterial combinations with known properties. The findings align with earlier research suggesting that breast milk bacteria help train the immune system and support healthy gut development. However, this is one of the first studies to systematically compare different functional types of breast milk bacteria and show they have different effects, which is a new contribution to the field.
This study was conducted in piglets, not human babies, so we cannot be certain the results will be identical in infants. The sample size of piglets was not specified in the available information, which makes it harder to assess statistical reliability. The study lasted only 24 days, so we don’t know if the benefits continue long-term or if the effects change as babies grow. The bacteria were added at specific laboratory-controlled amounts, which may not reflect how bacteria naturally behave in real formula or real digestive systems. Finally, this research doesn’t tell us whether these bacteria would be safe or effective in human infants, or whether formula companies could successfully add them to commercial products.
The Bottom Line
Based on this research, there is suggestive evidence that specific bacteria from breast milk may support infant gut and immune health. However, this is preliminary animal research. Current recommendation: Breastfeeding remains the gold standard for infant nutrition when possible. For formula-fed infants, standard infant formula continues to be safe and nutritionally adequate. Do not purchase unregulated probiotic supplements for infants without consulting a pediatrician. Wait for human clinical trials before expecting formula products with these specific bacteria to become available. If such products do become available in the future, discuss them with your pediatrician before use.
This research is most relevant to: parents of formula-fed infants, pediatricians and infant nutrition specialists, infant formula manufacturers, and public health officials developing infant nutrition guidelines. Parents of breastfed infants should know this research supports the benefits of breast milk but doesn’t require any action on their part. People with healthy digestive systems who are not infants should not assume these findings apply to them—infant gut health is very different from adult gut health.
This is very early-stage research. If these findings are confirmed in human babies through clinical trials, it would likely take 5-10 years before any new formula products incorporating these bacteria would be available to consumers. Even then, benefits would likely develop gradually over weeks to months as the bacteria establish themselves in the infant’s gut, not immediately.
Want to Apply This Research?
- For parents of formula-fed infants: Track infant digestive health markers weekly including stool consistency (using Bristol Stool Scale adapted for infants), frequency of bowel movements, signs of discomfort, and any digestive issues. Note any formula changes and correlate with digestive changes. This creates a personal baseline for your infant’s digestive health.
- If your infant is formula-fed, discuss with your pediatrician whether your current formula is meeting your baby’s needs. Keep detailed notes on your infant’s digestive health and immune function (frequency of infections, digestive comfort). When new probiotic-supplemented infant formulas become available, use the app to track whether they make any measurable difference in your infant’s health compared to their previous formula.
- Establish a long-term tracking system for infant digestive and immune health markers. Document stool patterns, infection frequency, and digestive comfort monthly. If formula changes are made, track for at least 2-4 weeks to assess any changes. Share this data with your pediatrician at regular check-ups to identify patterns and ensure your infant’s nutrition is supporting optimal development.
This research is preliminary animal-based science and has not been tested in human infants. Do not change your infant’s formula or add supplements based on this study without consulting your pediatrician. Infant formula should only be changed under medical guidance. If you have concerns about your infant’s digestive health or immune function, speak with your pediatrician. This article is for educational purposes and should not be considered medical advice. Always follow your pediatrician’s recommendations for infant nutrition and health.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.