Key Sugars in Breast Milk Support Toddler Gut and Brain Development After the First Year
Description
STORY AT-A-GLANCE
Human milk oligosaccharides (HMOs) are complex sugars that pass undigested to your baby’s colon, where they feed beneficial bacteria, strengthen defenses, and support healthy brain and immune development
A systematic review and meta-analysis in Frontiers in Pediatrics found that breast milk continues supplying substantial amounts of HMOs beyond 12 months, supporting gut health and brain development into toddlerhood
Certain HMOs, such as 3-fucosyllactose, even increase over time. This shows that the balance of individual sugars shifts across lactation and continues shaping your child’s development after infancy
Breast milk also contains myo-inositol, a sugar shown to boost synapse formation and neuronal connectivity, highlighting how breast milk delivers brain-supportive compounds beyond traditional nutrients
To keep your breast milk as nourishing as possible for your baby, prioritize whole foods, minimize unnecessary medications, and reduce toxin exposure. If breastfeeding isn’t possible, screened donor milk is the next best option
Breastfeeding is the most natural and powerful way to nourish an infant. In the United States, around 83% of babies begin life being breastfed, but the numbers fall quickly as the months pass. By six months, just over half of infants are still receiving breast milk, and by their first birthday, only about one-third continue.
These figures matter because breast milk is more than a source of calories.1 It maintains the ideal balance of nutrients while delivering a vast array of bioactive compounds that shape your child's growth and development. Among these compounds are human milk oligosaccharides (HMOs), complex sugars that rank as the third most abundant solid component in breast milk, surpassed only by lactose and lipids.2
A recent systematic review and meta-analysis published in Frontiers in Pediatrics explored how these core sugars influence gut and brain health beyond the first year of life. Their work highlights the significance of breastfeeding and why its benefits continue long after infancy, reinforcing the lasting foundation it helps create for your child's resilience and well-being.3
Study Shows Key HMOs Remain Abundant Beyond 12 Months
While the composition of early breast milk has been studied extensively, little was known about how these sugars persist later in lactation and whether they remain at meaningful levels. To address this gap, the featured study set out to determine which HMOs continue to appear in significant amounts after 12 months and to evaluate how concentrations change over time.
Systematic review and meta-analysis design — Researchers included only studies that measured HMOs at or beyond the one-year mark. Thirteen studies qualified, representing 4,786 milk samples collected across multiple countries. Concentrations were standardized into grams per liter (g/L), and when totals were missing, they were calculated by summing measured sugars.
<label class="hide-text" contenteditable="false">Text within this block will maintain its original spacing when published</label>This harmonization allowed comparison across analytical methods such as high-performance liquid chromatography and mass spectrometry.
Forty-two sugars were detected, but six stood out as "core" — Across all studies, 42 HMOs appeared at least once, yet only six consistently showed up in 10 or more publications. These were 2'-fucosyllactose (2'-FL), 3-fucosyllactose (3-FL), lacto-N-tetraose (LNT), lacto-N-neotetraose (LNnT), 3'-sialyllactose (3'-SL), and 6'-sialyllactose (6'-SL).
<label class="hide-text" contenteditable="false">Text within this block will maintain its original spacing when published</label>Together, they accounted for more than 70% of the total HMO pool at every stage of lactation, marking them as the dominant structures persisting into toddlerhood.
Overall HMO concentrations decreased, then stabilized — Total levels fell from 7.72 g/L in colostrum (the first nutrient-dense milk produced by the body in the days after birth) to 5.34 g/L at 12 months. However, measurements between 13 and 24 months averaged 8.47 g/L, ranging between 7.2 and 10.1 g/L. Although later data relied on fewer samples, the findings showed that breast milk continues to deliver substantial amounts of HMOs well into the second year.
Individual sugars followed distinct trajectories — 2'-FL remained the most abundant at all stages, averaging 3 g/L in colostrum and staying higher than 3-FL at 12 months (1.59 g/L vs. 1.45 g/L). 3-FL was unique in steadily rising, nearly quadrupling from 0.38 g/L in colostrum to 1.45 g/L at one year. By contrast, LNT and LNnT steadily declined, 6'-SL dropped sharply, and 3'-SL remained relatively stable.
<label class="hide-text" contenteditable="false">Text within this block will maintain its original spacing when published</label>These shifting trajectories suggest that while the total HMO pool remains steady, the balance of individual sugars evolves over time.
Persistence points to ongoing biological importance — HMOs are already linked to microbiome maturation, immune training, and neurodevelopment in infants, but little was known about their role after the first year. By showing that core HMOs remain abundant beyond 12 months, the study highlights a need to explore how ongoing exposure continues to shape gut and brain outcomes during toddlerhood.
Implications for feeding practices — For children who continue breastfeeding into the second year, HMOs remain available in biologically meaningful quantities. For those not breastfed beyond infancy, donor milk, fortified formulas, or HMO-enriched supplements, such as those containing 2'-FL and LNnT, provide alternate sources.
<label class="hide-text" contenteditable="false">Text within this block will maintain its original spacing when published</label>While long-term impacts require more research, the persistence of these sugars emphasizes their ongoing relevance during a period of rapid microbiome and brain development.
Taken together, these findings make it clear that breast milk continues to supply meaningful levels of core sugars well beyond the first year of life. Whether through continued breastfeeding, donor milk, or carefully chosen alternatives that include these compounds, ensuring steady access to these sugars may help support your child's health during the crucial months that follow infancy.
Why HMOs Matter for Growth and Li
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