The digestive flora refers to the collection of microorganisms that colonize the entire digestive tract—from the mouth to the colon. It is often equated solely with the gut microbiota, but it actually encompasses distinct ecosystems at each stage of the digestive tract. Its composition, diversity, and balance influence digestion, immunity, and daily digestive comfort. Explore our range of probiotics and prebiotics.
What is the digestive microbiota?
The digestive flora varies dramatically from one section of the digestive tract to another.
- Stomach: acidic pH (1.5–3.5) — very few bacteria (10³ CFU/mL), dominated by Helicobacter pylori in cases of pathogenic colonization
- Small intestine: pH 6–7, sparse flora (10³–10⁷ CFU/mL) — dominated by lactobacilli and enterococci, plays a role in nutrient absorption
- Colon: pH 5.5–7, extremely dense flora (10¹¹–10¹² CFU/mL) — primary site of the microbiome (Firmicutes, Bacteroidetes, Actinobacteria)
- Each section has its own specific probiotics—a “small intestine” formula (Lactobacillus) is not equivalent to a “colon” formula (Bifidobacterium)
Gut flora and digestion: what roles do they play?
The digestive flora plays a central role in food processing.
- Fermentation of indigestible fiber in the colon: production of butyrate (the main energy source for colonocytes), propionate, and acetate
- Hydrolysis of certain polyphenols into active metabolites (urolithins, equol)—the gut microbiota determines the benefits of dietary polyphenols
- Breakdown of residual lactose (in cases of mild intolerance) by lactic acid bacteria—see lactic acid bacteria
- Partial synthesis of vitamins K2, B7 (biotin), B9 (folate), and B12 in the colon
- Regulation of colonic motility via the production of gases (H₂, CO₂, methane) and enteric serotonin—direct influence on intestinal transit
Gut flora and allergies: what’s the connection?
The gut microbiota is one of the major determinants of allergic programming.
- The hygiene hypothesis: an impoverished microbiome in early childhood (excessive hygiene, early antibiotic use, formula feeding) is associated with an increased risk of food and respiratory allergies
- The gut microbiota modulates regulatory T cells (Tregs)—key cells in immune tolerance to food and airborne allergens
- Bifidobacteria (B. infantis, B. breve) play a well-documented role in reducing allergic responses in infants
- Early dietary diversification (as early as 4–6 months): introducing a variety of foods stimulates the diversity of the gut microbiota and reduces the risk of food allergies
- SCFAs (butyrate) produced by the microbiota regulate the expression of IgE—the key antibody involved in allergic reactions
Gut Flora and Probiotics: How Do They Work?
Probiotics and prebiotics are the best-documented ways to support the gut microbiota.
- For the small intestine: Lactobacillus acidophilus, L. plantarum —support for the mucosa and the digestion of lactose and fats
- For the colon: Bifidobacterium longum, B. bifidum —fiber fermentation and butyrate production
- Saccharomyces boulardii: antibiotic-resistant probiotic yeast—the gold standard for post-antibiotic recovery and traveler’s diarrhea
- Prebiotics (inulin, FOS, GOS, pectin): substrates for beneficial colonic bacteria — should always be included in comprehensive treatment regimens
- Glutamine: an amino acid found in the enterocytes of the small intestine — supports the integrity of the mucosal barrier
Diet and gut flora: what are the effects?
Diet reshapes the gut microbiota in just a few days—it is the most accessible lever.
- Varied fiber sources (30 different plant sources per week): each plant species feeds distinct bacteria—dietary diversity creates microbial diversity
- Fermented foods (yogurt, kefir, kimchi, raw sauerkraut): direct source of live bacteria and lactic acid, which modulates colonic pH
- Polyphenols (green tea, berries, dark cocoa, grapes): prebiotic substrates for certain beneficial colon bacteria—see polyphenols
- Reduce ultra-processed foods, refined sugars, and alcohol—documented disruptors of colonic diversity
- Seasonal variations: increase dietary variety in winter (legumes, cruciferous vegetables, nuts) to compensate for the decline in fresh fruits and vegetables
How can an imbalance in the gut microbiota be diagnosed?
Several levels of assessment can be used to objectively identify dysbiosis.
- Functional signs: chronic bloating, irregular bowel movements, persistent postprandial discomfort—the first accessible indicators
- Metagenomic stool analysis: mapping of present bacterial species and their relative abundance
- Fecal calprotectin: a marker of inflammation of the intestinal mucosa
- Hydrogen breath test: detects bacterial overgrowth in the small intestine (SIBO—Small Intestinal Bacterial Overgrowth)
- Normalized bowel movements and the resolution of bloating remain the most accessible daily indicators
