Common diets and gut microbiota

Complex carbohydrates have a big influence on the human gut microbiota. MAC or microbiota-accessible carbohydrates are carbohydrates that are resistant to digestion by the human body, and are made available for gut microbes, as prebiotics, to ferment or metabolize into beneficial compounds, such as short chain fatty acids (SCFAs).

The amount of carbohydrates accessible to gut microbes is affected by common dietary patterns that either increase, reduce or exclude specific nutrients.

The Western diet (high in animal protein and fat, low in MACs)

  • Leads to a decreased richness and diversity of total bacteria, especially beneficial Bifidobacterium, Lactobacillus and Eubacteria
  • MAC restriction leads to the use of intestinal mucus as the main source of energy by gut microbes due to compromised gut barrier integrity and reduced production SCFAs

Keto diet, with carbohydrate consumption of less than 10% of total caloric intake

  • The preclinical effects of Keto diet on beneficial gut microbes seems to indicate an overall reduction in gut microbiota diversity
  • Further studies are needed for exploring the diet’s long-term safety

Low FODMAP diet is a frequent treatment for irritable bowel syndrome (IBS)

  • The low-FODMAP diet may decrease beneficial bacteria including Bifidobacterium and Clostridium Cluster IV levels by limiting availability of fermentable carbohydrates
  • FODMAP restriction should be implemented in the short term, followed by reintroduction and personalization, with the support of medical professionals and dietary specialists

Mediterranean diet, characterized by greater vegetable intake vs animal protein

  • Shown to be the most adequate diet for preserving the diversity of gut microbes
  • Following the regular Mediterranean-like diet .
  • along with a prebiotic supplement may emerge as a potential dietary approach for improving abdominal pain and bloating
  • Greater adherence to the Mediterranean diet has been related with increased levels of fecal SCFAs and Lactobacillus, Bifidobacterium, Eubacteria, along with decreases in Clostridium
  • The diet’s beneficial impact on the gut microbiota could be explained by its capacity to improve lipid profile and inflammation

On the whole, sufficient inclusion of a variety of plant-based foods, rather than restrictive diets that exclude entire food groups, is the key to shaping high microbiota diversity.

Do you know the different types of gut bacteria? Read about them here.


  • Guarner, F; Malagelada, J (2003). “Gut flora in health and disease”. The Lancet.
  • Trichopoulou, A; Martínez-González, MA; Tong, TY; Forouhi, NG; Khandelwal, S; Prabhakaran, D; Mozaffarian, D; de Lorgeril, M (July 2014). “Definitions and potential health benefits of the Mediterranean diet: views from experts around the world”. BMC Medicine.
  • Cordain, L; Eaton, SB; Sebastian, A; Mann, N; Lindeberg, S; Watkins, BA; O’Keefe, JH; Brand-Miller, J (February 2005). “Origins and evolution of the Western diet: health implications for the 21st century”. The American Journal of Clinical Nutrition.
  • “Diet review: Ketogenic diet for weight loss”. TH Chan School of Public Health, Harvard University. 2019.
  • Barrett JS (March 2017). “How to institute the low-FODMAP diet”. Journal of Gastroenterology and Hepatology (Review).

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