A clinical trial shows 2′-FL and LNnT are safe for adults and increase beneficial bifidobacteria, offering a new way to support gut health.
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When it comes to human milk oligosaccharides (HMOs), you may associate them with nutrients that provide babies with the sustenance they need to grow. After all, these unique sugars are naturally found in breast milk and are famous for shaping the infant gut microbiome. But what about adults?
A clinical study by Elison and colleagues put this idea to the test by exploring what happens when healthy adults supplement two well-researched HMOs, 2’-fucosyllactose (2’FL) and lacto-N-neotetraose (LNnT) [1]. The results are promising and demonstrate that what’s good enough for babies could be good enough and more for adults who want to take care of their gut and beyond.
Inside the study: What the researchers did
To fully understand how HMOs might work in adults, the researchers designed a clinical trial involving 100 healthy men and women. They were randomly assigned to receive either:
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LNnT alone
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A placebo (glucose)
After a one- to two-week run-in period, participants then consumed their assigned supplement daily for 2 weeks at doses of 5g, 10g, or 20g, or 2g if they had received the glucose placebo. These doses were chosen because they are known to be within the daily dose range in infants per kilogram of body weight. No other dietary intervention took place, except that participants were asked not to change their diet while participating in the study.
The overall purpose of the study was to determine if:
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HMOs are safe and well-tolerated in adults
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HMOs shift the balance of the adult gut microbiota in a meaningful way
Are HMOs safe for everyday use in adults?
One of the key findings from the study was the high tolerability of the HMOs, 2’-FL, and LNnT. All of the study participants completed the trial, with a total of 56 adverse events reported. However, these were reported by 44% of participants and were reported as being mild, mostly in those ingesting the highest doses of the HMOs.
Some of the side effects reported were:
Those taking 20g of 2’FL, 20g of LNnT, and 5g of LNnT experienced an increase in the number of daily bowel movements. However, blood and faecal biomarker analysis demonstrated that the HMO supplementation was safe and raised no red flags at any of the doses.
How HMOs impact the adult gut: A microbiome makeover
Although safety and tolerability are essential, one of the major findings from the study is how HMOs can reshape the adult microbiome in as little as two weeks. The study found that these unique sugars can increase Bifidobacteria, reduce the abundance of pathogenic microbes, and promote a healthier gut balance, promoting their potential as powerful prebiotics for long-term digestive wellness.
Increased Bifidobacteria abundance
One of the key findings of the study was the increase in Bifidobacteria. The researchers found that 77% of participants had an increased abundance of Bifidobacteria by at least 10%, and some even found these colonies increased by a whopping 25%, as shown in fig.1.
Figure 1. Relative abundance of faecal bacteria before and after the intervention. The figure shows that only Bifidobacteria were significantly increased during the intervention with 10g of HMO.
This finding is significant because Bifidobacteria are considered a critical health-promoting genus in the gut. It is also one of the earliest colonizers in the infant colon. Low levels of this genus are found in:
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obese and overweight individuals [2]
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type 2 diabetes [3]
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antibiotic use [4]
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irritable bowel syndrome [5]
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inflammatory bowel disease [6]
More recent research published in 2024 by Firrman and colleagues, demonstrated that 2’FL supplementation increased Bifidobacteria abundance across all ages, from toddlers up to 70 year old adults [7].
Interestingly, the study also found that the operational taxonomic units (OTU) shared a strong similarity with a specific Bifidobacteria strain called Bifidobacteria adolescentis – a strain that isn’t known to metabolise HMOs. However, the researchers noted that the OTU could be another member of the Bifidobacteria family.
Therefore, safe supplementation of HMOs could be beneficial for individuals with these conditions, helping to replenish their Bifidobacteria colonies. This was demonstrated in a later study by Iribarren et al (2020), who found that supplementation with a 4:1 mix of 10g 2’FL and LNnT increased Bifidobacteria levels without worsening gastrointestinal symptoms in IBS patients. The researchers concluded that this approach could be a useful way to help IBS sufferers achieve a healthier gut microbiome profile [8].
Rebalancing the microbiome
As well as an increase in Bifidobacteria, a modest reduction in Firmicutes and Proteobacteria was also observed. Some members of these groups have been linked to poor metabolic health and inflammation. In the study, the increased abundance of Bifidobacteria and the reduction in Firmicutes and Proteobacteria occurred within 1 to 2 weeks. Why is this significant?
A higher Firmicutes-to-Bacteroidetes ratio is commonly associated with obesity [9], although this relationship is complex. For example, some research indicates that obese individuals often have a higher proportion of Firmicutes and a lower abundance of Bacteroidetes, suggesting that this ratio could be a potential marker of obesity [10].
Proteobacteria, on the other hand, include pathogenic species such as Salmonella, Helicobacter, Escherichia, and Campylobacter [11], and are often increased in disease, serving as a predisposing factor in the onset of disease [12].
Although figure 1 shows that only Bifidobacteria were significantly increased with the 10g of HMO. There were slight increases in Akkermansia.
Akkermansia is a next-generation probiotic known for its beneficial effects on the gut lining, as it feeds on mucins, thereby strengthening the gut barrier. It’s also been shown in previous research to utlize HMOs like 2’FL and LNT to thrive in the infant gut [12].
Why this matters for you
Understanding how HMOs like 2’FL and LNnT influence the adult gut isn’t just interesting, it has real-life implications, too. By boosting Bifidobacteria levels and promoting a more balanced microbiome, HMOs can support your digestion, immunity, and long-term wellness. Here’s why the results from this study could matter for your everyday health:
More bifidobacteria, better balance
Low levels of Bifidobacteria have been associated with conditions ranging from obesity and type 2 diabetes to inflammatory bowel disease and irritable bowel syndrome. By enriching these microbes safely, HMOs could offer a new dietary tool for nudging the gut ecosystem toward resilience and balance.
Targeted support without disruption
Unlike some broad-spectrum prebiotics that can cause excessive gas or diarrhea, HMOs in this study provided targeted support – boosting Bifidobacteria while leaving other beneficial microbes untouched. That selectivity is valuable for people seeking gut support without unpleasant side effects.
Beyond infancy
Until now, HMOs have been mostly associated with infant formula. This study demonstrates that their benefits don’t stop at weaning – they could play a role throughout adulthood. From supporting everyday gut comfort to potentially helping restore balance after antibiotics, HMOs may be valuable far beyond their original reputation.
Summary
This study provides insight into the fact that HMOs like 2’FL and LNnT are promising for adult gut health. They’re safe, well tolerated, and capable of enriching Bifidobacteria, the kind of microbiome shift many of us would welcome. Therefore, supplementing your diet with a mix of 2’FL and LNnT, like with our PureHMO® IBS Support, can help restore and maintain balance if you have dysbiosis or an imbalanced microbiome.
Some of the key findings from this study are summarised below:
✅ High doses of 2’FL and LNnT are safe and well-tolerated, and result in 100% compliance.
✅Up to 25% increase in Bifidobacteria.
✅ Reduced abundance of pro-inflammatory and poor health-associated bacteria.
✅ Insignificant increase in health-promoting Akkermansia, often associated with lean individuals.
Written by: Leanne Edermaniger, M.Sc. Leanne is a professional science writer who specializes in human health and enjoys writing about all things related to the gut microbiome.
