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Being born into a less affluent family, rather than a wealthy one, can have a detrimental effect on a child’s health [1]. For example, children from families of lower socioeconomic status have an elevated risk of asthma [2],  obesity [3], and behavioral and mental health challenges [4]. 

Researchers have explored many reasons for why socioeconomic status, an accident of birth that isn’t rooted in biology,has such clear biological effects. These include less access to healthcare, worse nutrition, and higher family stress [5]. Now, a new study reports a surprising link in the other direction: Breastfeeding may protect babies and young children from these detrimental outcomes,and it seems to do so by helping beneficial bacteria in the gut microbiome flourish. [6] 

A growing body of studies suggest that socioeconomic status can affect infants’ and children’s microbiome [7], but in this study, the researchers set out to show how socioeconomic status, childhood disease risk and the microbiome overlap and influence each other. 

“We wanted to understand how differences in early-life conditions shape children’s health, and how we might interrupt that cycle,” Stuart Turvey, a professor of pediatrics at the University of British Columbia who co-led the study, said in a statement from the university.

To probe these connections, Turvey and his colleagues analyzed data from more than 2700 children in the CHILD Cohort Study, the largest study in Canada to follow children from before birth to age five, and their families. 

The researchers began by combining responses to five markers of socioeconomic status, such as household income and parents’ educational attainment, into a single score. This  score was associated with differences in several factors tracked from pregnancy to age 1, such as birth weight and parents’ health, as well as chronic diseases and other health outcomes by age 5. Infants from more well-off families were significantly less likely to be overweight or to have emotional and  behavioral problems.

Because infants’ microbiomes are sensitive to factors related to socioeconomic factors, the team then analyzed gene profiles of almost 1500 stool samples from babies in the CHILD study. They identified a relationship between socioeconomic factors, gut microbiome, and breastfeeding. After examining the link between a range of factors in prenatal and early postnatal life, the researchers found that breastfeeding was most strongly associated with a higher diversity of bacteria in young infants’ microbiomes. It also appeared to be most strongly linked with lower risk of chronic conditions such as asthma and obesity in children. That protective effect was particularly pronounced in children from lower income families. 

The researchers confirmed these associations in a Danish cohort of 700 mother-child pairs. They noted that the results add to their earlier work, which found that breastfeeding protected babies’ microbiomes from the negative impacts of taking antibiotics [8]. The team’s analysis also honed in on one species of gut bacteria in particular, Bifidobacterium infantis, that was associated with an especially strong protective effect against health outcomes that can be affected by socioeconomic status. 

The gut microbiome of infants who were breastfed during their first year of life had more of this bacterium,  but it was also more abundant in children from families with higher socioeconomic status, even when breastfeeding was accounted for. This suggests that it’s not just breastfeeding that boosts the presence of B. infantis in the developing gut microbiome. 

Indeed, the researchers found that several other factors in a child’s surroundings, including whether their mother smoked, the number of older siblings they had, and the density of trees in their neighborhood, also affected the extent to which it was present in the gut microbiome. That aligns with other research reporting that despite its beneficial effects on babies’ health, this bacterium’s presence in the microbiome has decreased in industrialized countries [9]].  

 Overall, the researchers note that their findings aren’t just a call for encouraging mothers to breastfeed but rather underscore the importance on a societal level of enabling breastfeeding,  or finding other ways to bolster the infant microbiome,  to level the playing field on health outcomes for children across the socioeconomic spectrum. 

References

1. Poulain T, Vogel M, Kiess W. Review on the role of socioeconomic status in child health and development. Curr Opin Pediatr. 2020 Apr;32(2):308-14. 
2. Ellison-Loschmann L, Sunyer J, Plana E, Pearce N, Zock JP, Jarvis D, Janson C, Antó JM, Kogevinas M; European Community Respiratory Health Survey. Socioeconomic status, asthma and chronic bronchitis in a large community-based study. Eur Respir J. 2007 May;29(5):897-905. 
3. Ismail SU, Asamane EA, Osei-Kwasi HA, Boateng D. Socioeconomic determinants of cardiovascular diseases, obesity, and diabetes among migrants in the United Kingdom: a systematic review. Int J Environ Res Public Health. 2022 Mar 5;19(5):3070. 
4. Reiss F, Meyrose AK, Otto C, Lampert T, Klasen F, Ravens-Sieberer U. Socioeconomic status, stressful life situations and mental health problems in children and adolescents: Results of the German BELLA cohort-study. PLoS One. 2019 Mar 13;14(3):e0213700. 
5. Yang YC, Schorpp K, Boen C, Johnson M, Harris KM. Socioeconomic status and Biological risks for health and illness across the life course. J Gerontol B Psychol Sci Soc Sci. 2020 Feb 14;75(3):613-24. 
6. Dai DLY, Manus MB, Hoskinson C, Jiang J, Sbihi H, Miliku K, Campisi SC, Korczak DJ, Duan Q, Moraes TJ, Mandhane PJ, Finlay BB, Simons E, Lishman H, Patrick DM, Subbarao P, Azad MB, Chawes B, Bønnelykke K, Sørensen SJ, Thorsen J, Stokholm J, Petersen C, Turvey SE. Breastfeeding may lessen socioeconomic disparities in child health through differences in the infant gut microbiome. Cell Rep Med. 2026 Apr 21;7(4):102755. 
7. Lewis CR, Bonham KS, McCann SH, Volpe AR, D’Sa V, Naymik M, De Both MD, Huentelman MJ, Lemery-Chalfant K, Highlander SK, Deoni SCL, Klepac-Ceraj V. Family SES Is Associated with the Gut Microbiome in Infants and Children. Microorganisms. 2021 Jul 28;9(8):1608. 
8. Dai DLY, Petersen C, Hoskinson C, Del Bel KL, Becker AB, Moraes TJ, Mandhane PJ, Finlay BB, Simons E, Kozyrskyj AL, Patrick DM, Subbarao P, Bode L, Azad MB, Turvey SE. Breastfeeding enrichment of B. longum subsp. infantis mitigates the effect of antibiotics on the microbiota and childhood asthma risk. Med. 2023 Feb 10;4(2):92-112.e5.
9. Seppo AE, Bu K, Jumabaeva M, Thakar J, Choudhury RA, Yonemitsu C, Bode L, Martina CA, Allen M, Tamburini S, Piras E, Wallach DS, Looney RJ, Clemente JC Järvinen KM. Infant gut microbiome is enriched with Bifidobacterium longum ssp. infantis in Old Order Mennonites with traditional farming lifestyle. Allergy. 2021 Nov;76(11):3489-3503. 

Consuming maternal milk offers children many short and long-term benefits, as it supports cognitive development, immune programming, and the development of the gut microbiome. But the sub-cellular mechanisms that drive the varied health effects are yet to be fully elucidated. 

One possibility is the epigenome. Adding chemical tags to DNA can significantly alter the functions of genes, and the “epigenome,” which captures the entirety of these chemical decorations, can play a significant role in driving health outcomes. In a new study, researchers investigated whether breastfeeding was associated with DNA methylation,  one form of epigenetic modification, in children’s blood. 

Although some previous studies have examined whether methylation  mediates breastfeeding’s protective effects, the evidence has been inconsistent. Two studies, for example, identified a connection between breastfeeding and changes in methylation of the leptin gene, which produces a hormone that controls appetite and feeding. But the data were from small cohorts of participants, and correlations were not replicated across different studies.  

In the new work, researchers conducted a meta-analysis of data from approximately one dozen birth cohorts, the “largest investigation to date” of the link between breastfeeding and epigenetic changes, they wrote in their study [1]. They included data from more than 3,400 children across fourteen international cohorts from the Pregnancy And Childhood Epigenetics (PACE) Consortium. The analysis revealed several positive associations between DNA methylation at specific sites and duration of exclusive breastfeeding. 

The researchers’ data spanned methylation patterns in blood DNA samples from children  between ages five and twelve. They also used data from several cohorts that sampled cord blood at birth, which represents the neonatal epigenome prior to any feeding, as a negative control.

The team placed samples into various categories based on the duration and extent of breastfeeding. One group had no history of breastfeeding, and another had some history of consuming maternal milk, whether from a milk bank or via breastfeeding, in combination with formula or other foods. A third category included those who were exclusively breastfed for some period of time. The last group was further ranked based on the duration of exclusive breastfeeding. 

In their analysis, the researchers identified six methylated sites in children’s blood DNA that were positively associated with breastfeeding. Some were linked to exclusive breastfeeding, and others were more strongly correlated with a longer duration of exclusive breastfeeding. They did not identify any methylation patterns specifically unique to samples from the “some” breastfeeding group, where children had received some combination of breastmilk and other foods for a span of time. None of the sites they identified were significantly methylated in the cord blood samples collected prior to feeding. Some of the DNA regions identified as likely important are associated with “related to developmental and immune processes,” according to the researchers. 

The researchers noted various limitations of their data. Ten of the sampled cohorts were of European ancestry, and three cohorts had fewer than 100 participants. Overall, the significance of DNA methylation differences between the different breastfeeding categories was fairly small, and each month of exclusive breastfeeding did not strengthen the association. The team also found great variability across cohorts. For example, one association they identified for methylation at a specific location in DNA “seems to go in the opposite direction to the one expected for the known protective effects of breastfeeding on inflammation.”  As such, it is difficult to know for sure whether specific DNA methylation patterns help mediate the benefits of consuming maternal milk early in life. 

While no specific DNA methylation signatures were identified as significant, the data hint at possible associations that future studies could examine more closely. The researchers’ data was wide-ranging and comprehensive  and included children between the ages of five and twelve with a very wide range of exposures to maternal milk. By homing in on samples gathered earlier in life and including a narrower range of definitions of breastfeeding, it’s possible that future studies may identify more specific and significant DNA methylation patterns linked to maternal milk consumption. 

References

1. Caramaschi D, Fernández-Barrés S, Casey E, Cruells A, Czamara D, Sharkawy ME, Elliott HR, Fore R, Gairola R, Gruzieva O, Huels A. Breastfeeding association with DNA methylation in the pregnancy and childhood epigenetics (PACE) consortium. Clin epigenetics. 2026 Feb 28; 18(1):63

Genomics provides the blueprint of our DNA, allowing researchers to map the exact sequences of the As, Cs, Ts, and Gs that make up our genes and chromosomes. In the same way, the science of lipidomics maps the distinct lipid molecules, such as fatty acids, within a particular tissue, cell, or fluid. But while the human genome was sequenced 20 years ago, researchers are only now decoding the complex lipid library inside of our brains, eyes, adipose tissue, and milk. 

Lipidomics has ushered in a milk lipid science renaissance. New analytical tools, specifically liquid chromatography-mass spectrometry (LC-MS), have increased our understanding of the complexity of milk fatty acids by orders of magnitude and revealed that the diversity of milk lipids rivals the complexity of DNA and proteins [1, 2]. Indeed, milk fat is the most complex fat in nature [3]. 

In 2020, an international team of researchers performed the most comprehensive comparative lipidomic study to date on mammalian milk, identifying 472 distinct classes of fat and species-specific patterns in fatty acid composition in milk fat triglycerides from seven species of mammal [4]. Now, that same team has applied their advanced analytical tools to investigate the relationship between a species’ milk fatty acid composition and the types of fatty acids in the infant’s brain [5]. 

This is Your Brain on Milk

Mammalian brains are composed of mostly fat, which makes up roughly two-thirds of the brain’s dry weight [6]. Fatty acids, particularly long-chain polyunsaturated fatty acids (LCPUFA), are critical for brain growth and development. When delivered in mother’s milk, these fatty acids support a growing infant’s brain as structural building blocks. They are particularly critical nutrients for mammals who complete most of their brain growth during lactation, like humans. Human infants are born with brains only 25% of adult brain size and continue the fetal rate of brain growth for the first 18 months of life [7]. 

Despite knowing how important milk lipids are for brain growth and development, there has been no systematic investigation of how milk and brain fats correspond during infancy across mammals. Armed with high resolution techniques for identifying and quantifying a large array of fatty acids, Dr. Aleksandra Mitina, Postdoctoral Fellow in the Genetics and Genome Biology Program at the Hospital for Sick Children in Toronto, and her colleagues set out to test the hypothesis that milk lipid composition evolved to match the lipid requirements of the developing brain [5]. 

“We predicted that species with a greater proportion of postnatal brain growth should show a stronger correspondence between milk and brain lipid composition compared with species where the brain growth is completed at birth,” explains Mitina.

To test this prediction, the research team analyzed 837 milk samples from two human populations (Moscow, Russia and Shanghai, China; n=588), cows (n=103), goats (n=35), pigs (n=49), yaks (n =15), rhesus macaque monkeys (23), and crab-eating macaque monkeys (n=22) and 194 infant brain samples from humans (multiple ethnicities; n=92), chimpanzees (n=18), rhesus macaque monkeys (n=38), goats (n=26), and pigs (n=20) [5]. Milk samples and infant brain samples were unrelated for species that provided both types of samples. As a result, the study could not directly test for the relationship between a particular mother’s milk lipid composition and her infant’s associated brain lipid composition. Instead, they investigated between-species comparisons to identify potential ancestral patterns across mammals and species-specific adaptations in milk and brain fatty acids [5]. 

Using LC-MS analyses, researchers identified 81 distinct fatty acids in milk and 33 distinct fatty acids in brains, with 31 fatty acids shared across both tissues [5]. Clear patterns related to evolutionary relatedness were identified for both milk and brain fatty acid profiles. Milk fatty acids were more similar among bovids (cows, yaks, and goats), who had higher amounts of short-chain fatty acids and odd-chain unsaturated fatty acids, and among primates (rhesus macaques, crab-eating macaques, and humans), who had more even-chained polyunsaturated fatty acids (PUFA) and a few unique odd-chain PUFA [5]. Some of these were very-long-chain (24 – 27 carbons) and ultra-long-chain fatty acids (28 or more carbons) that have only recently been identified in mammalian milk [8, 9]. 

Brain fatty acids varied by species and by infant brain age, with humans showing higher levels of long-chain PUFA and ultra-long-chain fatty acids than brains of chimpanzees and macaque monkeys [5]. Across the three primate species, the abundance of long chain unsaturated fatty acids in both the brain’s pre-frontal cortex and cerebellum increased with infant age [5]. These temporal changes could be due to accumulation of maternally transferred fatty acids. Additional explanations could be changes in the composition of milk fatty acids, changes in how fatty acids are incorporated into brain tissue, or even increased production of fatty acids by the infant.

As Mitina and colleagues predicted, milk and brain fatty acid composition were significantly correlated across the four mammals, with the strongest correlations found in humans and macaques [5]. Between-species comparisons of milk and brain fatty acids also found that primates had the most substantial correlation; differences between the fatty acids in human and macaque brains were the strongest predictors of differences between fatty acids in human and macaque milk compared with all other between-species comparisons. These human-macaque correlations were strongest in the pre-frontal cortex region of the brain during the first four weeks of postnatal life and the cerebellum during the first two weeks of life, indicating the first month could be a particularly critical window for delivery of milk fatty acids in primates [5]. 

One of These Milks is Not Like the Other

The researchers identified a potentially conserved pattern across mammals (milk and brain lipids correspond) and a derived pattern among primates (milk and brain lipids are most strongly correlated in primate species, suggesting a greater dependence of primate infant brains on milk fatty acids). But perhaps their most intriguing finding was at the species level: human milk and brain were uniquely enriched in very-long-chain and ultra-long-chain fatty acids [5].  Although it is tempting to conclude that the enrichment of human milk with these unique fats evolved specifically to fuel human infant brain growth, this is still a hypothesis, and more research is needed to confirm this direct link.

Surprisingly little is known about these carbon-heavy lipids. The influence of the environment and genetics on the composition of fatty acids with 22 or fewer carbons in human milk is well studied, but very-long-chain and ultra-long-chain fatty acids have only recently been identified and quantified in human milk. Because these fatty acids are found in only specific types of tissues, including brains, retinas, and testes, they are believed to be important for supporting membrane fluidity, the formation of new neural synapses, and as signaling molecules [5]. 

“Ultra-long-chain fatty acids are present [in human milk] at very low levels compared to major fatty acids such as DHA [docosahexaenoic acid, 22:6n-3] or AA [arachidonic acid, 20:4n-6]. Much less is known about the ultra-long-chain fatty acids we highlighted, including 26:1, 27:1, 28:1, and 28:2. These fatty acids are rarely measured, and we don’t know much about the extent of variation in human populations or their response to diet,” says Mitina.

However, the fact that the study identified a strong correlation between human milk and brain fatty acids despite the milk and brains coming from different human cohorts suggests that these very-long-chain and ultra-long-chain fatty acids could be independent of factors that strongly influence DHA or AA composition, such as maternal diet and genetics. Another explanation, says Mitina, is that “whatever dietary and genetic variation exists may be smaller than the differences between humans and the other mammals included in this study.” 

Without a full understanding of how and why very-long-chain and ultra-long-chain fatty acids vary across human populations (or among mammal species) it is not possible to say definitively that their enrichment in human milk is a species-specific trait. “As of now,” says Mitina, “the comparative data that we have is too limited to say if the human pattern represents an extreme point along the development, or if it’s a unique feature of our lineage”

The study also does not speak to which mechanism (or mechanisms) would be uniquely present in humans to increase the concentration of very-long-chain and ultra-long-chain fatty acids in milk. Mitina doesn’t believe that human mammary glands have unique enzymes for adding carbons to fatty acid chains from the maternal bloodstream. Instead, she speculates that humans could differ from other primates in the regulation of these enzymes by the mammary gland or in the transport of certain fatty acids from maternal bloodstream to milk. 

“Our study produced a hypothesis that humans may have specific regulation of certain ultra-long-chain fatty acids,” explains Mitina. “And now, testing this hypothesis will require measuring of these lipids across human populations and studying the genetic and biochemical pathways involved in their synthesis, transport, and incorporation into milk and brain.”

The Tip of the Milk/Brain Iceberg

Mitina et al. [5] made an exciting discovery: human milk has a potentially unique enrichment of very-long-chain and ultra-long-chain fatty acids, and these same fatty acids are also uniquely found in human infant brains. But the research team can’t rest on their laurels. As characteristic of any good science, their novel finding generates more questions than answers.

Mitina shared that she and her research team have several projects on the horizon to investigate evolutionary modifications to human milk composition. To understand how very-long-chain and ultra-long-chain fatty acids may differ within and between human populations, the researchers will collaborate with a large, longitudinal study on infant and child health that can provide access to milk samples with corresponding data on diet, environmental factors known to influence milk composition, and maternal genetics. They also plan to conduct experimental research in mouse models to better understand the potential mechanisms responsible for enriching milk with very-long-chain and ultra-long chain fatty acids.

We are only just beginning to grasp the staggering complexity of milk lipid composition. Every new discovery simply underscores how much we still have left to learn. Just as deciphering the human genome required decades of dedicated research, fully mapping the vast network of milk lipids will be time-consuming. But the results will be equally valuable for understanding human evolution. 

References

1. Zhang X, Liu L, Wang L, Pan Y, Hao X, Zhang G, Li X, Hussain M. Comparative lipidomics analysis of human milk and infant formulas using UHPLC-Q-TOF-MS. J  Agric  Food Chem. 2021 Jan 19; 69(3):1146-55.
2. Ahrends R, Baker ES, Ekroos K, Ellis SR. New Analytical Technologies to Resolve, Interpret, and Understand Lipid Complexity. Annu Rev of Anal Chem. 2026 Feb 24;19.
3. Liu Z, Rochfort S, Cocks B. Milk lipidomics: What we know and what we don’t. Prog in Lipid Res. 2018 Jul 1; 71:70-85.
4. Mitina A, Mazin P, Vanyushkina A, Anikanov N, Mair W, Guo S, Khaitovich P. Lipidome analysis of milk composition in humans, monkeys, bovids, and pigs. BMC Evol Biol. 2020 Jun 19;20(1):70
5. Mitina A, Wang Y, Mair W, Vanyushkina A, Anikanov N, Efimova O, Guo S, Mazin P, Khaitovich P. Comparative analysis of milk and brain fatty acids reveals human-specific signatures in brain development. Commun Biol. 2026 Apr 22.
6. Chang CY, Ke DS, Chen JY. Essential fatty acids and human brain. Acta Neurol Taiwan. 2009 Dec 1;18(4):231-41.
7. Milligan LA. Do bigger brains mean better milk? In: Clancy KBH, Hinde K, Rutherford JN, editors.  Building Babies: Primate development in proximate and ultimate perspective. New York (NY): Springer; 2012. p.209-231.
8. Kyselová L, Vítová M, Řezanka T. Very long chain fatty acids. Prog Lipid Res. 2022 Jul 1; 87:101180.
9. Koulman A, Furse S, Baumert M, Goldberg G, Bluck L. Rapid profiling of triglycerides in human breast milk using liquid extraction surface analysis Fourier transform mass spectrometry reveals new very long chain fatty acids and differences within individuals. Rapid Comm Mass Spectrom. 2019 Aug 15;33(15):1267-76.

Childhood obesity remains a pressing public health issue. According to the CDC, nearly 1 in 5 children and adolescents aged 2 through 19 have obesity in the U.S. [1]. This can lead to health problems later in adulthood, including diabetes, cardiovascular disease, musculoskeletal disorders, and certain types of cancer [2].

Traditional dietary guidance in the U.S. has been to consume low-fat or fat-free dairy products to help limit saturated fat intake [3]. It wasn’t until earlier this year that the Dietary Guidelines for Americans strongly recommended full-fat dairy products [3].  

There is a growing body of evidence suggesting that full-fat dairy may not be as harmful as we think. One study reported that overweight adults who consumed three servings of full-fat dairy did not experience negative effects on their body weight or select metabolic markers. Another study found that consumption of whole milk lowered children’s risk of obesity in early adolescence. 

The American Academy of Pediatrics has even recommended that children only drink whole fat milk until they are about 2 years old, unless there is a reason to switch sooner, such as a family history of obesity or heart disease [4]. The aim is to reduce childhood obesity; however, these guidelines are based on studies from adults, and children require plenty of nutrients while they are developing.

Few studies had explored how milk-fat intake affects rates of obesity in children, but new research from the University of Toronto has found that whole milk consumption in children at age 5 years is associated with lower adiposity and obesity at age 8 [5]. 

“This is regardless of the child’s socioeconomic status, ethnicity, physical activity, and other factors that influence growth,” says the lead researchers of the study, Dr. Kozeta Miliku, assistant professor in nutritional sciences; Dr. Tara Zeitoun, a post-doctoral fellow; and Zheng Hao (Howard) Chen, a PhD student at the University of Toronto. 

The team used data from the Canadian Healthy Infant Longitudinal Development (CHILD) Cohort Study, one of the largest Canadian population-based pregnancy cohort studies which has enrolled participants across 4 different sites in Canada. They assessed the children’s milk-fat intake, along with their height, waist circumference, waist-to-height ratio z-score, fat mass percentage, BMI, blood pressure, and metabolic factors at ages 5 years then 8 years [5]. 

In addition, the research team used recent guidelines from the Lancet Diabetes & Endocrinology Commission to help define preclinical and clinical obesity in children. This definition is more stringent than that of the World Health Organization, which only measures BMI. The Lancet Commission goes beyond BMI by requiring confirmation of excess adiposity through measurements of body size or body fat mass percentage. It also considers health factors that are a result of having obesity, such as elevated blood pressure or high cholesterol [6]. 

“BMI does not distinguish between fat and muscle mass,” says Miliku, Zeitoun, and Chen, “so a child with more muscle mass may be grouped in the same obesity category as a child with more fat mass … These nuances in obesity classification can help unmask the true effect of diet on childhood obesity development by isolating the effect of body fat mass from muscle mass.”

The researchers found that consumption of whole milk fat at age 5 years was consistently associated with a lower risk of obesity at age 8 years. The children had lower measures of adiposity including BMI z-score, waist-to-height ratio z-score, and fat mass percentage [5]. The data highlight the importance of a more holistic approach to a healthy diet as opposed to strictly cutting out fat. 

“The findings were surprising in the sense that whole milk has traditionally been viewed as something that could contribute to excess weight gain in children because of its higher fat and calorie content,” explains Miliku, Zeitoun, and Chen. “However, our findings are also consistent with a growing body of pediatric research suggesting that whole-fat dairy may not increase obesity risk in children and may even be associated with healthier body composition outcomes.” 

“Children are not simply ‘small adults,’” the researchers add. Given that pediatric guidelines are often extrapolated from adult studies, “we may need to re-evaluate whether current recommendations fully reflect the best available evidence in children.” Indeed, this is particularly important as children continue to grow and establish eating habits that may influence their health later in life. 

The CHILD Cohort Study uniquely positions the research team to follow study participants’ health trajectories long-term. The team plans to assess whether the association between milk-fat intake and obesity persists into adolescence. They are also interested in exploring how dairy fat may influence cardiometabolic pathways and overall dietary patterns.   

Because this was an observational study, Miliku and colleagues recognize that a randomized, controlled clinical trial is needed to determine causality between milk-fat content and obesity. 

Nevertheless, “our findings contribute to the growing evidence base that can help inform future pediatric nutrition guidelines and public health recommendations.” 

References

1. Stierman B, Afful J, Carroll MD, Chen T-C, Davy O, Fink S, et al. National Health and Nutrition Examination Survey 2017–March 2020 prepandemic data files-development of files and prevalence estimates for selected health outcomes. Natl Health Stat Report. 2021 June 14;(158):1-21. 
2. Sahoo K, Sahoo B, Choudhury AK, Sofi NY, Kumar R, Bhadoria AS. Childhood obesity: Causes and consequences. J Family Med Prim Care. 2015 Apr-Jun;4(2):187-92. 
3. U.S. Department of Agriculture; Department of Health and Human Services.Dietary guidelines for Americans, 2020-2025  [Accessed May 30, 2026]. Available from: www.dietaryguidelines.gov.
4. Porto A, Drake R. Cow’s milk alternatives: Parent FAQs: American Academy of Pediatrics; 2022 [Accessed May 30, 2026]. Available from: https://www.healthychildren.org/English/healthy-living/nutrition/Pages/milk-allergy-foods-and-ingredients-to-avoid.aspx.
5. Zeitoun T, Chen ZH, Burgner D, MacKechnie G, Huntington P, Mansell T, et al. Milk fat intake, adiposity, and obesity in Canadian children: Findings from the prospective Canadian CHILD Cohort Study. Am J Clin Nutr. 2026 May;123(5):101186.
6. Rubino F, Cummings DE, Eckel RH, Cohen RV, Wilding JPH, Brown WA, et al. Definition and diagnostic criteria of clinical obesity. Lancet Diabetes Endocrinol. 2025 Mar;13(3):221-62.