According to Gram Research analysis, human milk oligosaccharides (HMOs), natural compounds in breast milk, may help protect developing brains from the effects of high-fat, high-sugar diets by changing how reward-related genes work in the brain. In a 2026 animal study, young rats given HMO supplements showed altered gene expression in brain regions controlling food cravings, and female rats ate slightly less sugar when later exposed to unhealthy food. However, this effect was modest and temporary, and more human research is needed.
A new study shows that compounds found in breast milk, called human milk oligosaccharides (HMOs), might help protect developing brains from the effects of eating too much fatty and sugary food. Researchers gave young rats supplements containing two types of HMOs and then fed them a high-fat, high-sugar diet. They found that the HMO supplements changed how certain brain genes worked, particularly in areas that control cravings and emotions. The effects were different for male and female rats, and the dose of HMO mattered. This research suggests that what babies eat early in life could have lasting effects on their food choices and mental health as they grow up.
Key Statistics
A 2026 animal study found that female rats receiving high-dose human milk oligosaccharide supplements showed lower expression of glutamate receptor genes in the nucleus accumbens, a brain region involved in food reward and motivation.
In a 2026 research article published in Physiology and Behavior, female rats that received human milk oligosaccharide supplements consumed less sugar than control rats on the first day of testing, though this difference disappeared by the second day.
A 2026 study demonstrated that the effects of human milk oligosaccharide supplementation on brain gene expression and eating behavior were both sex-dependent and dose-dependent, with female rats showing more pronounced responses than males.
The Quick Take
- What they studied: Whether giving young rats supplements of breast milk compounds (HMOs) could protect their brains from the effects of eating a high-fat, high-sugar diet as they grow older.
- Who participated: Young Sprague-Dawley rats (a common laboratory rat breed) that received HMO supplements after weaning and were later fed a high-fat, high-sugar diet. The study looked at both male and female rats.
- Key finding: Rats that received HMO supplements showed changes in how their brain genes worked, especially genes related to wanting food and processing emotions. Female rats that got higher doses of HMOs ate slightly less sugar on their first day of testing.
- What it means for you: Early nutrition may shape how our brains respond to junk food later in life. This suggests that breast milk compounds could have protective effects, though more research in humans is needed before making any dietary changes.
The Research Details
Researchers studied young rats after they stopped nursing, giving some of them supplements containing two types of human milk oligosaccharides (HMOs): 2’-fucosyllactose and 3’sialyllactose. These are natural compounds found in human breast milk. The rats received different doses of these supplements. After the supplementation period, all the rats were fed a high-fat, high-sugar diet similar to many processed human foods. The researchers then measured how much the rats ate, what foods they preferred, and how anxious they seemed. Most importantly, they examined the rats’ brains to see how certain genes were working in specific brain regions involved in cravings and emotions.
The study was designed to answer two main questions: Does early HMO supplementation affect food choices and anxiety later in life, and can HMOs protect against the effects of eating unhealthy food? The researchers looked at both male and female rats separately because they suspected the effects might be different between sexes.
This type of animal research is important because it allows scientists to study brain changes and gene expression in ways that would be impossible in humans. The findings can then guide future human studies.
Understanding how early nutrition affects brain development is crucial because the brain is still developing during childhood and early life. If compounds in breast milk can protect the developing brain from the effects of unhealthy food, this could have major implications for infant nutrition and long-term health. This research also helps explain why breastfeeding has been linked to better health outcomes in children.
This study was published in a peer-reviewed scientific journal, meaning other experts reviewed the work before publication. The researchers used a controlled laboratory setting where they could carefully measure variables. However, this is animal research, so results may not directly apply to humans. The study did not specify the exact number of rats used, which makes it harder to assess the statistical power. The findings are preliminary and would need to be confirmed in human studies before making any recommendations.
What the Results Show
The most striking finding was that HMO supplementation changed how genes worked in the nucleus accumbens, a brain region involved in reward and motivation. This effect was different in male and female rats, and it depended on how much HMO the rats received. In female rats that got the highest dose of HMOs, genes related to glutamate receptors (brain chemicals involved in learning and memory) were expressed at lower levels when they were later exposed to the high-fat, high-sugar diet.
When it came to actual eating behavior, the effects were modest. Female rats that received HMO supplements ate slightly less sugar than control rats on the first day of testing, but this difference disappeared by the second day. This suggests that HMOs might provide some short-term protection against sugar cravings, but the effect may not last long once rats are exposed to unhealthy food.
All rats, regardless of whether they received HMO supplements, showed a strong preference for the high-fat, high-sugar food over regular food. This suggests that once rats are exposed to this type of diet, they want it, even if they had early protective factors. The researchers think this happens because the unhealthy diet changes how the brain values different foods, making junk food seem more rewarding.
The study found that anxiety-like behaviors were not significantly affected by HMO supplementation, suggesting that the main effects were on brain regions related to food reward rather than emotional processing. The sex-specific differences were notable: female rats showed more response to HMO supplementation than males, particularly in terms of gene expression changes. This suggests that early nutrition may affect male and female brains differently, possibly due to hormonal differences.
Previous research has shown that HMOs support immune system development and gut health in infants. This study extends that knowledge by suggesting HMOs also affect how the brain develops and responds to food. The finding that early nutrition influences later food preferences aligns with other research showing that early-life experiences shape lifelong eating habits. However, this is one of the first studies to look at how HMOs specifically affect brain gene expression related to food reward.
This study was conducted in rats, not humans, so the results may not directly apply to people. The exact number of rats used was not specified, making it difficult to assess how reliable the findings are. The study only looked at two types of HMOs, but there are many different HMOs in breast milk, so the effects might be different with other types. The high-fat, high-sugar diet used in the study was given to adult rats, not young rats, so it does not perfectly mimic what happens when children eat unhealthy food. Finally, the study measured gene expression in the brain but did not directly measure brain function or long-term health outcomes.
The Bottom Line
Based on this research, there is not yet enough evidence to recommend HMO supplements for children or adults. The study was in animals and showed only modest effects on behavior. However, the findings support the importance of breastfeeding when possible, since breast milk naturally contains HMOs. If you are interested in protecting your child’s brain development and future food choices, breastfeeding for at least the first six months of life remains the best-supported approach. For families who cannot breastfeed, infant formulas with added HMOs are becoming available, though more research is needed on their effectiveness.
Parents and caregivers should care about this research because it suggests that early nutrition has lasting effects on brain development and food preferences. Healthcare providers may find this useful when counseling families about infant feeding. Researchers studying nutrition, brain development, and obesity should pay attention to these findings. People interested in understanding why some individuals struggle with food cravings may find this research relevant. However, this research is not yet ready to guide individual dietary decisions.
In this animal study, the effects on brain gene expression were visible within weeks to months. However, behavioral effects on eating were modest and sometimes temporary. If similar effects occur in humans, changes in food preferences might develop over months to years. Long-term benefits for mental health and metabolism would likely take even longer to become apparent.
Frequently Asked Questions
Can I give my baby HMO supplements to prevent them from liking junk food later?
This study was in rats, not humans, so we cannot yet recommend HMO supplements for this purpose. Breastfeeding naturally provides HMOs, and some infant formulas now include them. Talk to your pediatrician about whether HMO-supplemented formula is right for your family.
Does this research prove that breast milk prevents obesity?
No. This study shows that HMOs may affect how the brain responds to food, but the actual eating behavior changes were small and temporary. Breastfeeding has many benefits, but preventing obesity requires multiple factors including overall diet quality and physical activity.
Why did the study use rats instead of human babies?
Researchers use rats to study brain changes that would be impossible to measure directly in humans. Rats have similar brain structures and can be studied in controlled conditions. However, findings in rats do not always apply to humans, so human studies are needed next.
Are the effects of HMOs different for boys and girls?
Yes. This study found that female rats responded more strongly to HMO supplementation than males, particularly in terms of brain gene expression. This suggests early nutrition may affect developing male and female brains differently, possibly due to hormones.
If I breastfeed, will my child automatically have better food preferences?
Breastfeeding provides natural HMOs and other protective compounds, but it is not a guarantee against preferring unhealthy foods later. Children’s food preferences are shaped by many factors including what foods they are exposed to, family eating habits, and their environment.
Want to Apply This Research?
- Track your child’s food preferences and cravings over time, noting which foods they choose most often and how their preferences change. Record this weekly in a simple chart showing favorite foods, foods refused, and any changes in eating patterns.
- If breastfeeding, continue as long as feasible to ensure your child receives natural HMOs. If using formula, discuss HMO-supplemented options with your pediatrician. As your child grows, monitor their food choices and try to delay introduction of high-fat, high-sugar foods, since this study suggests early eating patterns may influence later preferences.
- Over months and years, track whether your child’s early nutrition (breastfeeding duration, formula type, introduction of solid foods) correlates with their later food preferences and eating habits. Note any patterns in cravings for sugary or fatty foods and whether they seem to have stronger or weaker preferences compared to peers.
This research was conducted in rats and has not been tested in humans. The findings are preliminary and should not be used to make medical decisions for yourself or your child without consulting a healthcare provider. If you are considering infant feeding options, breastfeeding choices, or dietary supplements, discuss them with your pediatrician or registered dietitian. This article is for educational purposes only and does not constitute medical advice.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.