Benefits
Bifidobacteria in the adult gut
In a 2-week placebo-controlled trial in 100 healthy adults, groups of ten taking 5, 10 or 20 g a day of LNnT alone had a larger rise in gut Bifidobacterium than the placebo group. This is a gut bacteria marker, not a measured health outcome, each dose group was small, and the trial was funded by the maker of the LNnT.
Bowel movement frequency and stool form in healthy adults
In the same 2-week trial, bowel movements rose from baseline by about 0.3 a day on 5 and 20 g a day of LNnT, a change the authors judged clinically irrelevant, and stools were softer than at baseline on 20 g, although the symptom questionnaire recorded harder stools in that group. These were within-group changes, not differences from placebo.
Bowel comfort with a 2'-FL and LNnT blend
In a 4-week placebo-controlled trial in 60 adults with IBS, a 4:1 blend of 2'-FL and LNnT at 5 or 10 g a day raised bifidobacteria at 10 g but did not change gut symptoms compared with placebo. A 12-week study of 5 g a day reported improvement from baseline but had no placebo group. LNnT was not tested on its own.
Gut bacteria in school-age children taking a two-HMO blend
In an 8-week placebo-controlled trial in 75 children aged 6 to 12 with overweight, bifidobacteria rose within the 2'-FL and LNnT blend group at 4 weeks, but the difference from placebo was only a trend (p = 0.071), while 2'-FL alone did raise them versus placebo. Both were well tolerated. The maker sponsored the trial.
Iron absorption from fortified porridge in infants
In a crossover study in Kenyan infants aged 8 to 12 months, adding 2 g of 2'-FL and 1 g of LNnT to an iron-fortified maize porridge did not change iron absorption compared with the porridge alone (median 13.3% vs 12.5%), while galacto-oligosaccharides did raise it. LNnT was not tested on its own.
Mechanism of action
Food for bifidobacteria
Gut bacteria such as Bifidobacterium can use milk oligosaccharides. In the adult trial, Bifidobacterium rose with all three LNnT doses, and the rise in Actinobacteria, the bacterial group that includes bifidobacteria, increased with dose for LNnT and 2'-FL alike, apart from 20 g of 2'-FL, which showed no rise. Firmicutes fell at the highest LNnT dose.
Laboratory findings on microbes and the gut lining
A review of laboratory and animal research describes LNnT blocking the attachment of some bacteria and viruses, changing immune cell signals and helping intestinal cells mature. These effects come from lab and animal work; none was measured in the human trials cited here.
Clinical trials
Randomized, double-blind, placebo-controlled, parallel dose-finding trial over 2 weeks: ten groups of ten took 2'-FL alone, LNnT alone or a 2:1 blend of the two at 5, 10 or 20 g a day, or 2 g glucose placebo (NCT01927900). The 2'-FL and the LNnT were both made by chemical synthesis. Funded by Glycom A/S, which employed three authors and paid three others as consultants (Elison et al. 2016, Br J Nutr)
100 healthy adults aged 18 to 60 in Denmark; all completed.
Bifidobacterium rose more than on placebo with 10 g of 2'-FL alone but not with 5 or 20 g of 2'-FL; it also rose with all three LNnT doses and with 10 or 20 g of the blend. All 56 adverse events were mild. At 20 g of 2'-FL alone, nausea, rumbling, bloating, gas, diarrhea, loose stools and urgency scored higher than on placebo, as did passing gas at 10 and 20 g of LNnT alone.
Randomized, double-blind, placebo-controlled parallel trial of a two-HMO blend (4:1 2'-FL and LNnT) at 5 or 10 g a day versus glucose for 4 weeks plus 4 weeks of follow-up; primary outcome fecal bifidobacteria (NCT02875847). Glycom A/S is listed as the grant source and employed four authors (Iribarren et al. 2020, Neurogastroenterol Motil)
60 adults with IBS diagnosed by Rome IV criteria in Sweden; 58 completed.
Bifidobacteria rose at week 4 with 10 g compared with the other groups, but not at week 8. Overall and individual gastrointestinal symptoms did not differ between groups at week 4 or 8, and symptoms did not worsen. 2'-FL was not tested on its own.
Open-label, single-arm multicenter trial with no placebo group: 5 g a day of a two-HMO blend (4:1 2'-FL and LNnT) for 12 weeks; primary outcome bowel habits (share of bowel movements with abnormal stool consistency) (NCT03550742). Sponsored by Glycom, Inc., which helped design the trial and write the paper; three authors were Glycom employees (Palsson et al. 2020, Clin Transl Gastroenterol)
317 adults with IBS at 17 US sites; 245 completed per protocol.
Abnormal stool consistency, symptom severity scores and quality of life improved from baseline, most in the first 4 weeks. Without a placebo group these changes cannot be attributed to the blend, and the authors called for a placebo-controlled trial. Common side effects were mild gas, abdominal pain and distension.
Randomized, double-blind, placebo-controlled trial of 2'-FL alone, a two-HMO blend of 2'-FL and LNnT, or glucose placebo once a day for 8 weeks; the daily dose and blend ratio are not stated in the abstract or the registry entry read. Registry NCT02786160 (Glycom A/S sponsor, three arms, 75 children; primary outcome change in fecal microbiota) matches, though the abstract does not cite it. Three authors were Glycom employees (Fonvig et al. 2021, J Pediatr Gastroenterol Nutr)
75 children aged 6 to 12 with overweight, including obesity, in Denmark.
Compared with placebo, bifidobacteria rose on 2'-FL alone at 4 and 8 weeks; on the blend the difference from placebo was only a trend (p = 0.071 at both times), though bifidobacteria rose within the blend group at 4 weeks. Blood tests raised no safety concerns, and gut symptom and stool form scores showed no tolerance problems.
Randomized, multicenter trial of formula with 1.0 g/L 2'-FL and 0.5 g/L LNnT, a two-HMO blend, versus the same formula without HMOs to 6 months; primary endpoint weight gain through 4 months (NCT01715246). Sponsored by Nestec Ltd., with several Nestle-employed authors (Puccio et al. 2017, J Pediatr Gastroenterol Nutr)
175 healthy infants aged 0 to 14 days (88 test, 87 control).
Weight gain met noninferiority. In secondary outcomes, parents reported less bronchitis and lower respiratory infection and less antibiotic and antipyretic use in the HMO group, which the authors said needs confirmation. Stools were softer at 2 months.
Randomized, double-blind, placebo-controlled trial in 7 French neonatal units: a two-HMO blend (10:1 2'-FL and LNnT) at 0.374 g/kg body weight a day or a glucose placebo until discharge; primary outcome noninferiority in days to full enteral feeding (NCT03607942). Funded by Société des Produits Nestlé, which took part in interpreting and writing; two authors had Nestlé affiliations (Hascoët et al. 2022, Front Pediatr)
86 preterm infants born at 27 to 33 weeks weighing under 1,700 g (43 per group).
Noninferiority for time to full enteral feeding was met; the HMO group reached it about 2 days sooner, a difference that was not significant (p = 0.177). Weight z-scores did not differ, while length and head circumference z-scores were higher at some time points. Adverse events were similar; related adverse events were 2.3% vs 14.3%. Growth and tolerance here are safety results.
Randomized, crossover stable-isotope study: test meals of maize porridge with 5 mg iron alone, with 3.0 g galacto-oligosaccharides, or with 2.0 g 2'-FL plus 1.0 g LNnT, a two-HMO blend; primary outcome fractional iron absorption (NCT04163406). Registry sponsor ETH Zurich; funding is not detailed in the abstract, and no author was listed with an HMO maker (Giorgetti et al. 2023, Am J Clin Nutr)
55 partially breastfed Kenyan infants aged 8 to 12 months; 49 were fed as instructed.
Iron absorption with the HMO blend (median 13.3%) did not differ from iron alone (12.5%; p = 0.923), while galacto-oligosaccharides raised it to 22.2%. Maternal milk HMO profile did not predict absorption. The authors concluded the data argue against a role for 2'-FL and LNnT in helping iron absorption in infancy.