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Unbalanced microbiota and disorders

Different parts of the human body (intestines, skin...) are home to living microorganisms (bacteria, fungi, viruses...) called microbiota, which are beneficial to our health when they are properly balanced. The disruption of this balance (referred to as dysbiosis) can be associated to several disorders, depending on the location of the affected microbiota. This is why gastroenteritis, Cohn’s disease, some gastrointestinal cancers, and even depression, diabetes, allergies and skin disorders such as eczema could be associated to microbiota imbalances. Let’s explore the link between microbiota and health!


The composition of a microbiota is characterized by its diversity (number of different species present in an individual) and its abundance (total number of microorganisms present). When this composition is disrupted (change in one or both of these factors), the balance is broken and a dysbiosis emerges. This dysbiosis can be associated to several diseases but it is yet uncertain whether it is a cause or a consequence of these diseases. So, which came first, the chicken or the egg? Science has not been able to answer this question. 



Drugs (antibiotics…)

Alcohol and tobacco



Bacterial, viral
or parasitic

Sudden change
in environment
or diet

Drugs (antibiotics…)

Different diseases

Alcohol and tobacco

Bacterial, viral or parasitic


Sudden change in environment
or diet


Good news! When the balance of a microbiota is compromised, it is possible to restore it by acting on its composition (abundance, diversity). It is called microbiota modulation. In practice, there are different ways to do so:

Through a balanced diet: low content of fat and carbohydrates and high content of fibers and foods like artichoke, garlic, onion (naturally rich in prebiotics) as well as sauerkraut, kefir, fermented dairy products (which are a source of probiotics).

By taking:

  • probiotics
  • prebiotics
  • synbiotics (combination of the former two)

In the most severe cases, restoring a healthy microbiota through fecal microbiota transplant is an alternative that has given promising results.

Sources :
The Human Microbiome Project Consortium. Structure, function and diversity of the healthy human microbiome. Nature 2012 ; 486(7402):207-14.
Jernberg C, Löfmark S, Edlund C, Jansson JK. Long-term impacts of antibiotic exposure on the human intestinal microbiota. Microbiology. 2010 ; 156 : 3216-23.
Martinez-Medina M, Denizot J, Dreux N, et al. Western diet induces dysbiosis with increased E. coli in CEABAC10 mice, alters host barrier function favouring AIEC colonisation. Gut. 2014 Jan; 63(1):116-24.
Lizko NN. Stress and intestinal microflora. Food Nahrung 1987 ; 31:443-447.
Manichanh C, Rigottier-Gois L, Bonnaud E, et al. Reduced diversity of faecal microbiota in Crohn’s disease revealed by a metagenomic approach. Gut. 2006 ; 55 : 205-11.
Amarthaluru S, Joseph C, Kovasevic D, et al. Gut microbiota dysbiosis in celiac disease: a review. Current Science Review, September 18, 2015.
Spiller R, Garsed K. Postinfectious irritable bowel syndrome. Gastroenterology. 2009 ; 136 : 1979-88.
Kabbani TA, Pallav K, Dowd SE et al. Prospective randomized controlled study on the effects of Saccharomyces boulardii CNCM I-745 and amoxicillin-clavulanate or the combination on the gut microbiota of healthy volunteers. Gut Microbes. 2016 : 1-16.
Bäckhed F, Ding H, Wang T, et al. The gut microbiota as an environmental factor that regulates fat storage. Proc Natl Acad Sci USA 2004 ; 101 : 15718-23.
Okada H, Kuhn C, Feillet H, et al. The “hygiene hypothesis” for autoimmune and allergic diseases: an update. Clin Exp Immunol 2010 ; 160 : 1-9.
Burcelin R, Zitvogel L, Fond G, et al. Dossiers d'information de l’INSERM « Microbiote intestinal et santé » - février 2016