The gut microbiota is the collection of microorganisms—bacteria, archaea, viruses, fungi, and protozoa—that inhabit the digestive tract. With more than 100,000 billion cells and over 1,000 identified species, it constitutes a true ecosystem whose diversity is the primary indicator of health. It plays a role in digestion, vitamin synthesis, immune regulation, and communication with the brain via the gut-brain axis. Explore our line of probiotics.
What is the gut microbiota?
The gut microbiota accounts for approximately 1.5 kg of total body weight. It is composed of 90% of two dominant bacterial phyla: Firmicutes (including Lactobacillus) and Bacteroidetes (including Bacteroides and Prevotella). The Firmicutes-to-Bacteroidetes ratio is a marker of the microbiome’s health—an imbalance in this ratio is associated with several metabolic disorders. Each individual has a unique microbiome, influenced by mode of delivery (vaginal vs. cesarean section), breastfeeding, diet from childhood onward, and adult lifestyle.
Microbiota and Immunity: What’s the Connection?
The microbiota plays a key role in the development and fine-tuning of the immune system.
- 70 to 80% of the body’s immune cells are found in the intestinal wall—the microbiome constantly trains them to distinguish self from non-self
- It stimulates the maturation of regulatory T cells (Tregs), which are essential for immune tolerance and the prevention of autoimmune responses
- Short-chain fatty acids (SCFAs) produced by fiber fermentation (particularly butyrate) nourish colonocytes and regulate the expression of immune genes
- Omega-3 EPA and DHA support the resolution of the intestinal immune response
- Zinc is essential for the integrity of the tight junctions in the intestinal barrier
Microbiota and the gut-brain axis?
The gut-brain axis is one of the most important discoveries in modern neurogastroenterology.
- 90% of the body’s serotonin is produced in the gut under the influence of the microbiome—a direct link between microbial balance and mood
- The vagus nerve transmits information from the microbiome to the brain in near real time
- Certain bacteria produce GABA, dopamine precursors, and neuroactive amino acids
- "Psychobiotics" (L. rhamnosus, B. longum) are being studied for their influence on the stress response and mental well-being
How can you disrupt or enrich your microbiota?
The microbiota is sensitive to many factors—some deplete it, while others increase its diversity.
- Disruptive factors: antibiotic therapy (loss of up to 30% of diversity), ultra-processed foods, chronic stress, a sedentary lifestyle, alcohol, and tobacco
- Enriching factors: varied fiber (aim for 30 different plants per week), fermented foods (yogurt, kefir, kimchi), regular moderate physical activity
- Prebiotics (inulin, FOS, GOS): selective substrates for bifidobacteria and lactobacilli
- Probiotics: repopulation with documented beneficial strains (Bifidobacteria, Lactobacillus)
- Glutamine: an amino acid found in enterocytes that maintains the integrity of the intestinal barrier
Microbiota and Vitamins: What Are the Endogenous Sources?
The microbiota synthesizes vitamins that diet alone does not always provide in sufficient quantities.
- Vitamin K2 (menaquinones MK-4 to MK-13): synthesized primarily by colonic bacteria (Bacteroides, Fusobacterium, Eubacterium)—plays a role in blood clotting and bone health
- B vitamins (B1, B2, B6, B9, B12): partially synthesized by bacteria—contribution varies depending on the composition of the microbiota
- Production depends directly on the diversity and abundance of beneficial bacteria—a depleted microbiome produces fewer vitamins
- These endogenous syntheses do not replace dietary intake but complement it
How can you assess the health of your microbiota?
Several levels of assessment are available depending on your goals.
- Functional signs: regular bowel movements, absence of chronic bloating, digestive comfort —early indicators of a balanced microbiome
- Metagenomic stool analysis (microbiome test): mapping of bacterial species present—available in a laboratory by prescription or through direct-to-consumer kits, depending on the kit
- Indirect markers: fecal calprotectin (intestinal inflammation), zonulin (intestinal permeability)
- Regular bowel movements and normal stool consistency remain the most accessible indicators in daily life
