A compound in breast milk called 2′-fucosyllactose (2′-FL) not only helps infants grow but may also improve memory in older adults.
A 2025 study from Stanford University found that supplementing 5 g of 2′-FL daily for six weeks doubled the gut population of Bifidobacteria in elderly participants, while also improving memory and metabolic indicators[1].
2′-FL in Breast Milk
Human milk oligosaccharides (HMOs) are the third most abundant component in breast milk, after lactose and lipids[2].
2′-FL is one of the most abundant HMOs. Composed of lactose linked to fucose, 2′-FL and lacto-N-tetraose are often added to infant formula as key HMO components.
(Figure: Chemical structure of 2′-FL; right: relative abundance of different HMOs in natural breast milk.)
Six Weeks of 2′-FL Boosts Gut Bifidobacteria
To study the physiological effects of 2′-FL in older adults, the Stanford team recruited 89 healthy elderly participants (average age 67), randomly assigning them to three groups:
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High dose: 5 g/day of 2′-FL
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Low dose: 1 g/day of 2′-FL
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Placebo: glucose without 2′-FL
The intervention lasted six weeks, with stool, blood, and urine samples collected to analyze gut microbiota, hormones, and metabolites. After six weeks, supplementation stopped, and follow-up tests were performed.
By the third week, Bifidobacteria counts surged dramatically in the high-dose group and continued increasing until week six. Once supplementation stopped, Bifidobacteria levels returned to baseline.
(Figure: Week 3 showed a sharp rise in Bifidobacteria in the high-dose group.)
What Are Bifidobacteria?
Bifidobacteria are core members of the human gut microbiota, with species composition shifting over a lifetime:
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Infancy & adolescence (0–17 years): Dominated by B. breve (33%), specialized in breaking down HMOs and supporting neural development[3].
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Adulthood (18–65 years): B. longum dominates (49%), followed by B. adolescentis (18%), adapted to diverse diets[3].
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Elderly (66–108 years): B. longum increases to 65%, but species diversity drops sharply, reducing health functions[3].
(Figure: Age-related changes in Bifidobacteria species diversity.)
Metabolic Benefits of 2′-FL
After six weeks of supplementation, elderly participants saw significant increases in two key biomarkers[1]:
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HDL cholesterol – the “vascular scavenger,” improving clearance of arterial plaques and reducing atherosclerosis risk.
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FGF21 (fibroblast growth factor 21) – a hormone secreted by the liver that regulates lipid metabolism, enhances fat breakdown, and boosts energy expenditure, helping prevent obesity and diabetes[4].
(Figure: Left – HDL increase after 2′-FL; Right – FGF21 increase after 2′-FL.)
However, immune response scores (CRS) did not significantly change across the three groups. CRS is linked to cardiovascular risk and aging, reflecting how quickly immune cells respond to cytokine signals[5].
Why Some Seniors Respond Better
Not all participants benefited equally. Scientists classified those whose Bifidobacteria levels rose above the average as “responders”, and others as “non-responders.”
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93.3% of responders already had Bifidobacteria before the trial, compared with 58.6% of non-responders.
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This suggests baseline presence of Bifidobacteria is key for effective growth after 2′-FL supplementation.
Responders also had higher blood 2′-FL concentrations and greater levels of immune pathway proteins. They showed higher SIRT2 protein levels—associated with anti-aging—than non-responders.
(Figure: Protein and metabolite correlations in responders vs. non-responders.)
2′-FL May Prevent Age-Related Osteoporosis
In aged mice, 12 weeks of 2′-FL supplementation increased bone mineral density (BMD) by ~20%.
While estrogen deficiency is a known osteoporosis driver, gut dysbiosis and immune imbalance are also hidden “bone killers.” 2′-FL improved intestinal barrier integrity, regulated innate immunity, and reduced inflammation that drives bone resorption[7].
(Figure: BMD increase after 12 weeks of 2′-FL in mice.)
Nurturing Gut Microbiota Early Pays Off in Old Age
From the first sip of breast milk, Bifidobacteria play a quiet but vital symphony of symbiosis.
The study shows elderly “responders” (those with baseline Bifidobacteria) benefited more from supplementation—highlighting the long-term value of nurturing gut microbiota early in life.
Caring for your gut flora when young may plant the seeds for health in later years.