Mechanism of Action
Once ingested, GOS resist gastric digestion and small intestine enzymes. They reach the colon intact. There, specific bacterial families possess the enzymes needed to break them down. This process, called selective fermentation, produces short-chain fatty acids (molecules with two, three or four carbons).
Butyrate provides energy to the cells lining the colon wall. These cells form a barrier between intestinal contents and the bloodstream. The more intact this barrier, the fewer unwanted molecules pass through.
The growth of beneficial bacteria acidifies the intestinal environment. This lower pH inhibits potentially harmful species. The prebiotic effect reshapes the entire ecosystem, beyond merely feeding a few strains.
Key Benefits
- Strong
More bifidobacteria in the colon, within the first week of intake: controlled trials in healthy adults measure this increase reproducibly, from 1.3 g to 15 g per day.
- Moderate
Less bloating, gas and abdominal pain: a double-blind crossover trial in 83 adults with daily discomfort measures this decrease from the first week, at 2.75 g per day.
- Moderate
More active immune markers in older adults: a double-blind crossover trial in 44 volunteers measures increased phagocytic activity (cells' ability to engulf intruders) after ten weeks, at 2.75 g per day.
- Emerging
Lower waking cortisol, the morning stress hormone: a three-week randomized trial observes this in healthy volunteers, at 2.75 g per day.
- Emerging
Better-hydrated skin: a twelve-week controlled trial in 79 adults aged 30 to 69 measures increased skin hydration and reduced water loss, at 2 g per day.
Dosage & Forms
Commercial GOS vary in their polymerisation profile, that is, the distribution of sugar chain lengths. Short chains (DP2-3) dominate the market. Extended-spectrum blends (DP2-8) show a more pronounced bifidogenic effect in clinical trials, meaning stronger stimulation of bifidobacteria.
Comparing doses across trials calls for care: commercial materials do not all assay the same. Several reference trials administer 5.5 g of a blend that delivers only 2.75 g of actual GOS. Expressed as actual GOS, the literature spans 1.3 g to 15 g per day, and the effect on bifidobacteria is already measurable at 1.3 g.
The doses used rise markedly with the effect under study: trials targeting stool frequency go up to 11 g per day, those on iron absorption to 15 g, and those measuring calcium absorption to 20 g. Gradual increase over five to seven days limits initial digestive discomfort.
In the Singular Formula
Inclusion rationale
Non-digestible prebiotic fibers produced by enzymatic transgalactosylation of lactose. GOS (galacto-oligosaccharides) are structurally similar to human milk oligosaccharides (HMOs), the natural fibers that shape the infant microbiota from the very first hours of life. Not digested in the small intestine, GOS reach the colon intact where they are selectively fermented by bifidobacteria and lactobacilli, the bacterial genera that are pillars of a balanced microbiota. This fermentation produces short-chain fatty acids (butyrate, propionate, acetate), energy sources for colonocytes and modulators of intestinal pH. Butyrate nourishes the cells of the colonic mucosa. GOS differ from FOS (fructo-oligosaccharides) in their galactosidic structure, which gives them superior digestive tolerance with less bloating. In the formula, GOS act upstream of the microbiota by feeding each person's resident bifidobacteria, without relying on colonization delivered by the supplement. Acacia fiber completes this system through slower, more gradual fermentation. This network approach aims to support microbiota diversity, whose decline is a marker of biological aging.
Selected form
Vivinal® GOS is a concentrated soluble galacto-oligosaccharide fibre produced using proprietary enzymatic technology. These non-digestible prebiotics serve as a selective substrate for beneficial gut bacteria, particularly bifidobacteria. The ingredient contains a spectrum of oligosaccharide chains from DP2 to DP8, or 2 to 8 galactose units. Its taste is slightly sweet. Derived from milk lactose, this powder consists of 97% milk solids: 69% GOS, 23% lactose and other disaccharides, and 5% glucose and galactose.
Formula dosage
0 to 5 g.
Dose expressed as active substance, excluding excipients and carriers of the raw material.
Synergies in the formula
Safety & Precautions
GOS have a long history of safe use. Naturally present in breast milk as structurally similar oligosaccharides, they are part of human nutrition from birth. Trials report favourable tolerance up to 15 g per day, adverse effects being limited to mild bloating or flatulence, transient and reduced by gradual introduction over five to seven days.
GOS belong to the FODMAP family, fermentable carbohydrates that some people tolerate poorly. In adults with irritable bowel syndrome, a crossover study reports increased digestive discomfort on a GOS-rich diet. The health profile collects this situation, and GOS are then excluded from the formula.
The material selected is derived from milk lactose and retains a measurable fraction of it: 5 g of GOS corresponds to about 7.2 g of powder, of which roughly 1.7 g is lactose and other disaccharides. Milk is declared as a constituent allergen.
GOS are not recommended for people with galactosemia (a rare genetic condition that prevents galactose metabolism). Pregnant or breastfeeding women can consume them as part of a balanced diet.
Scientific Studies
| Authors | Year | Type | Journal | |
|---|---|---|---|---|
| Looijesteijn E et al. | 2024 | Randomised Controlled Trial | Frontiers in Nutrition | View on PubMed |
A double-blind intervention trial in healthy women demonstrates the beneficial impact on Bifidobacterium with low dosages of prebiotic galacto-oligosaccharides Double-blind randomized trial in 88 women aged 42 to 70: 1.3 g and 2.0 g of GOS per day for three weeks significantly increase fecal bifidobacteria. | ||||
| Vulevic J et al. | 2018 | Randomised Controlled Trial | Neurogastroenterology & Motility | View on PubMed |
Effect of a prebiotic galactooligosaccharide mixture (B-GOS) on gastrointestinal symptoms in adults selected from a general population who suffer with bloating, abdominal pain, or flatulence Double-blind crossover trial in 83 adults with bloating, flatulence or abdominal pain: 2.75 g of GOS per day lower all three scores from the first week. No effect on the number of bowel movements or on stool consistency. | ||||
| Schoemaker MH et al. | 2022 | Randomised Controlled Trial | Nutrients | View on PubMed |
Prebiotic Galacto-Oligosaccharides Impact Stool Frequency and Fecal Microbiota in Self-Reported Constipated Adults: A Randomized Clinical Trial Randomized trial in 132 self-reported constipated adults: at 5.5 g per day, no effect on stool frequency; at 11 g, a trend only. Stool consistency is unchanged at either dose, while bifidobacteria do follow the dose. | ||||
| Vulevic J et al. | 2008 | Randomised Controlled Trial | The American Journal of Clinical Nutrition | View on PubMed |
Modulation of the fecal microflora profile and immune function by a novel trans-galactooligosaccharide mixture (B-GOS) in healthy elderly volunteers Double-blind crossover trial in 44 elderly volunteers: 5.5 g of B-GOS mixture per day, that is 2.75 g of actual GOS, for ten weeks increase phagocytic activity, NK cell activity and interleukin-10. No effect on total or HDL cholesterol. | ||||
| Vulevic J et al. | 2015 | Randomised Controlled Trial | British Journal of Nutrition | View on PubMed |
Influence of galacto-oligosaccharide mixture (B-GOS) on gut microbiota, immune parameters and metabonomics in elderly persons Double-blind crossover trial in 40 volunteers aged 65 to 80: ten weeks of GOS increase bifidobacteria, NK cell activity and interleukin-10, but also C-reactive protein. | ||||
| Wilms E et al. | 2021 | Randomised Controlled Trial | Clinical Nutrition | View on PubMed |
Galacto-oligosaccharides supplementation in prefrail older and healthy adults increased faecal bifidobacteria, but did not impact immune function and oxidative stress Crossover trial in 20 prefrail older adults and 24 healthy adults: 15 g of GOS per day increase bifidobacteria, but change neither immune function markers nor oxidative stress markers. | ||||
| Davis LM et al. | 2011 | Randomised Controlled Trial | PLoS ONE | View on PubMed |
Barcoded pyrosequencing reveals that consumption of galactooligosaccharides results in a highly specific bifidogenic response in humans Study using pyrosequencing in 18 healthy adults, at 2.5, 5 and 10 g per day: GOS produce a highly specific bifidogenic response, selectively increasing certain bifidobacterial species. | ||||
| Schmidt K et al. | 2015 | Randomised Controlled Trial | Psychopharmacology | View on PubMed |
Prebiotic intake reduces the waking cortisol response and alters emotional bias in healthy volunteers Randomized trial in 45 healthy volunteers, fifteen per group: three weeks of GOS reduce waking salivary cortisol and decrease attentional bias toward negative stimuli. | ||||
| Johnstone N et al. | 2025 | Randomised Controlled Trial | Brain, Behavior, and Immunity | View on PubMed |
A randomised controlled trial of the effects of Galacto-Oligosaccharides on the gut brain-axis of young females Randomized controlled trial in 83 women aged 17 to 25: after 28 days of GOS, trait anxiety, the study's primary outcome, does not differ from placebo. | ||||
| Hong YH et al. | 2017 | Randomised Controlled Trial | Asia Pacific Journal of Clinical Nutrition | View on PubMed |
Dietary galacto-oligosaccharides improve skin health: a randomized double blind clinical trial Double-blind randomized trial in 79 adults aged 30 to 69: 2 g of GOS per day for twelve weeks increase skin hydration and reduce water loss. Wrinkled surface area also decreases; wrinkle depth and number do not change. | ||||