Research shows that babies with slow growth have different bacteria in their guts than normally growing babies, but the specific foods they eat don’t directly explain these bacterial differences. According to Gram Research analysis of a 2026 case-control study of 300 Indonesian babies, breastfeeding was the strongest factor shaping which bacteria babies had, suggesting that breast milk’s unique components matter more than individual food choices for developing healthy gut bacteria.
Researchers in Indonesia studied 300 babies (150 pairs) to understand why some children grow slower than others. They looked at the tiny bacteria living in babies’ stomachs and what foods the babies ate. According to Gram Research analysis, while babies with growth problems had different bacteria than healthy babies, the specific foods they ate didn’t directly change which bacteria were present. However, breastfeeding made a big difference in the types of bacteria babies had. The study suggests that understanding how food, bacteria, and growth connect is more complicated than scientists previously thought.
Key Statistics
A 2026 case-control study of 300 babies in East Lombok, Indonesia found that six types of bacteria (Agathobacter, Coprococcus, Dorea, Hominimerdicola, Lawsonibacter, and Ruminococcoides) were significantly more abundant in normally growing children compared to those with stunted growth.
In the same study of 300 babies aged 18-23 months, breastfeeding significantly shaped microbiota profiles, making it the strongest dietary factor influencing which bacteria colonized babies’ guts, more influential than specific complementary food groups.
Research from 150 matched pairs of stunted and non-stunted children found no significant differences in overall bacterial diversity between the two groups, indicating that growth problems involve changes in bacterial composition rather than reduced bacterial variety.
The Quick Take
- What they studied: Whether the bacteria in babies’ guts are different between children who grow normally and those who grow slowly, and whether different foods change these bacteria.
- Who participated: 300 babies between 18-23 months old living in East Lombok, Indonesia—150 with slow growth (stunted) and 150 with normal growth, matched by age and location.
- Key finding: Babies with slow growth had different types of bacteria in their guts compared to normally growing babies, but the foods they ate didn’t directly explain these differences. Breastfeeding was the strongest factor shaping which bacteria babies had.
- What it means for you: If you have a baby with growth concerns, understanding their gut bacteria might help doctors in the future, but simply changing foods alone may not be the answer. Breastfeeding appears to be especially important for healthy gut bacteria development.
The Research Details
This study compared two groups of babies: those with stunting (slow growth) and those growing normally. Researchers measured each baby’s height and weight, asked parents detailed questions about what their babies ate, and collected stool samples to analyze the bacteria living in their guts. They used advanced genetic testing to identify which bacteria were present and in what amounts.
The study was carefully designed by matching babies in the stunted group with babies in the normal growth group based on age and location. This matching helps ensure that any differences found are more likely due to growth status rather than other factors like where the babies live.
Researchers collected information about breastfeeding, formula feeding, and introduction of solid foods. They then compared the bacteria profiles between the two groups to see if certain bacteria were more common in one group than the other.
Understanding the connection between what babies eat, the bacteria in their guts, and how they grow is important because it could eventually help doctors prevent or treat growth problems. This study used a careful comparison approach that allows researchers to identify real differences between groups, making the findings more reliable than simple observations.
This study was published in a highly respected scientific journal (Philosophical Transactions of the Royal Society B), which means it went through expert review. The researchers used modern genetic sequencing technology to identify bacteria accurately. However, the study was conducted in one specific region of Indonesia, so results may not apply equally to all populations worldwide. The study design (case-control) is good for identifying differences but cannot prove that one thing directly causes another.
What the Results Show
The research found that babies with slow growth had different bacteria in their guts compared to babies growing normally. Specifically, six types of bacteria (Agathobacter, Coprococcus, Dorea, Hominimerdicola, Lawsonibacter, and Ruminococcoides) were more common in normally growing babies, while a bacteria called Peptostreptococcus was more common in babies with slow growth.
Surprisingly, when researchers looked at what foods the babies ate—including vegetables, fruits, grains, and proteins—they found no direct connection between these foods and the different bacteria present. This was unexpected because scientists previously thought that diet would be the main factor shaping which bacteria live in babies’ guts.
The strongest factor the researchers found was breastfeeding. Babies who were breastfed had noticeably different bacteria profiles compared to babies who weren’t breastfed, regardless of whether they had growth problems or not. This suggests that breast milk contains special components that directly influence which bacteria thrive in a baby’s gut.
The study found that the overall diversity of bacteria (how many different types were present) was similar between the two groups. This means that babies with slow growth didn’t necessarily have fewer types of bacteria—they just had different proportions of certain types. The researchers also noted that the relationship between bacteria and growth is likely more complex than previously understood, possibly involving how different foods work together rather than individual foods alone.
Previous research had shown that stunted and non-stunted children have different bacteria, but this study goes further by examining how diet connects to these differences. The finding that diet alone doesn’t explain the bacterial differences challenges earlier assumptions and suggests scientists need to look at more complex patterns, such as how multiple foods interact together. The strong effect of breastfeeding confirms what other research has suggested about breast milk’s importance for healthy gut development.
This study was conducted only in East Lombok, Indonesia, so the results may not apply to babies in other countries or regions with different diets and environments. The study design captures differences at one point in time but cannot show whether the bacteria differences cause slow growth or result from it. The researchers didn’t have detailed information about the exact nutrients in the foods babies ate, only which food groups were consumed. Additionally, the study couldn’t fully capture how different foods work together in babies’ diets, which the researchers suggest is important for future studies.
The Bottom Line
Based on this research, breastfeeding should remain a priority for infant health and gut development (high confidence). While changing individual foods may not directly alter gut bacteria, maintaining overall good nutrition remains important for growth. Parents and healthcare providers should not assume that simply adding more vegetables or other foods will fix growth problems—a more comprehensive approach involving healthcare professionals is needed (moderate confidence).
Parents of babies under 2 years old, especially those with growth concerns, should understand this research. Healthcare workers in developing countries where stunting is common should pay attention to these findings. This is less immediately relevant to parents in wealthy countries where stunting is rare, though the science of infant gut health applies broadly.
Changes to infant gut bacteria happen gradually over weeks to months. If breastfeeding is started or continued, parents might expect to see shifts in bacterial composition within 4-8 weeks, though visible growth improvements take longer (3-6 months minimum) and depend on many factors beyond just bacteria.
Frequently Asked Questions
Does what my baby eats change the bacteria in their stomach?
A 2026 study of 300 babies found that specific foods didn’t directly change which bacteria were present. However, breastfeeding significantly shaped bacterial profiles, suggesting breast milk’s components matter more than individual foods for developing healthy gut bacteria in babies under 2.
Why do some babies not grow as fast as others?
This research shows that babies with slow growth have different bacteria in their guts, but the connection is complex. The bacteria differences alone don’t fully explain slow growth—other factors like overall nutrition, health, and environment also play important roles.
Is breastfeeding important for my baby’s gut health?
Yes. A 2026 study of 300 Indonesian babies found that breastfeeding was the strongest factor shaping which bacteria lived in babies’ guts, more influential than any specific food. This supports continuing breastfeeding as long as possible for healthy gut development.
Can I fix my baby’s growth problems by changing their diet?
Diet is important, but this research suggests it’s more complicated than simply adding certain foods. Babies with growth problems need comprehensive evaluation by healthcare providers, as the connection between diet, bacteria, and growth involves multiple factors beyond individual food choices.
What bacteria should be in my baby’s gut?
Normally growing babies tend to have more Agathobacter, Coprococcus, Dorea, and related bacteria, while babies with slow growth more often have Peptostreptococcus. However, having different bacteria doesn’t automatically mean a problem—healthcare providers should evaluate the full picture of your baby’s health.
Want to Apply This Research?
- Track breastfeeding duration and frequency daily, noting when solid foods are introduced and which food groups are offered. Record baby’s weight and length monthly to monitor growth patterns alongside feeding changes.
- If breastfeeding, continue as long as possible while gradually introducing recommended complementary foods around 6 months. Document which foods baby tolerates well and growth measurements to share with healthcare providers.
- Create a monthly growth chart showing weight and length trends. Maintain a feeding log noting breastfeeding sessions, formula amounts, and foods introduced. Share this data with pediatricians to identify patterns and ensure baby is growing appropriately.
This research describes associations between gut bacteria and growth in babies under 2 years old in Indonesia and should not be used to diagnose or treat growth problems. If you have concerns about your baby’s growth, weight gain, or development, consult with your pediatrician or healthcare provider immediately. This article summarizes research findings and is not a substitute for professional medical advice. Individual babies vary greatly, and what applies to the study population may not apply to your specific child.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.