The Mediterranean diet has long been associated with a lower risk of lifestyle-related diseases and better overall health. In recent years, however, it has increasingly been suggested that part of these benefits may be mediated by the gut microbiome — the community of microorganisms that inhabit our intestines and play a crucial role in the functioning of the body.
The Gut Microbiome: Why It Matters
The human digestive tract is home to more than a thousand species of microorganisms — bacteria, viruses, and other microscopic forms of life. Together, they carry millions of genes, far more than the human genome contains.
The microbiota plays a role in:
- fermenting indigestible components of food, especially fiber,
- producing short-chain fatty acids (e.g., butyrate, propionate, and acetate),
- regulating inflammation and immune responses.
Disruption of the microbiome’s balance (so-called dysbiosis) has been associated with local inflammation of the intestinal lining, metabolic disorders, and a range of intestinal and extraintestinal diseases. However, it is important to note that the composition of the microbiota varies significantly between individuals, and there is no single “ideal” microbiome for everyone.
The Role of Diet
Diet is one of the most important factors influencing the composition of the microbiome. Research in both animals and humans shows that changes in dietary patterns can lead to shifts in the abundance of specific bacterial groups as well as in their metabolic activity.
In this respect, the Mediterranean diet is particularly interesting because it is rich in complex carbohydrates, plant fiber, and bioactive compounds that serve as substrates for fermentation by gut bacteria.
What Studies Show About the Mediterranean Diet and the Microbiome
1) Higher microbial diversity (α-diversity)
In a prospective study of healthy adults, higher microbiome α-diversity was observed in individuals with good adherence to the Mediterranean diet. They showed greater species richness and a different abundance of certain bacterial genera (e.g., Paraprevotella, Bacteroides). PubMed Central
2) Differences in specific bacterial groups
Evidence suggests that the Mediterranean diet is associated with a higher abundance of beneficial short-chain fatty acid (SCFA)-producing bacteria, such as Bifidobacterium, Faecalibacterium prausnitzii, and Roseburia. These bacteria help maintain the intestinal barrier and may exert anti-inflammatory effects. PubMed
3) Modulation of microbial balance
A systematic review including both randomized controlled trials (RCTs) and observational studies suggests that the Mediterranean diet influences microbiota composition and metabolite production (e.g., SCFAs), although findings are not always consistent due to differences in study design. PubMed
4) Rapid changes following dietary intervention
Small pilot studies indicate that switching to a Mediterranean-style diet can relatively quickly alter microbial diversity and the abundance of specific bacterial genera, even in healthy individuals during short intervention periods. PubMed Central
5) Associated metabolic and physiological effects
Research summarizing available data reports that the Mediterranean dietary pattern is linked not only to microbiome changes but also to improved glycemic control, reduced inflammation, and better metabolic homeostasis — likely partly mediated by SCFA production and the promotion of beneficial microbial communities. PubMed
6) Differences compared to a “Western” diet
Some studies show that individuals whose eating patterns more closely resemble the Mediterranean diet have a microbiome distinct from those consuming a typical Western diet (rich in ultra-processed foods and saturated fats). The Mediterranean-associated microbiome is generally considered more health-supportive. PubMed
7) Effects on functional metabolic pathways
Studies have also shown that the Mediterranean diet alters not only the composition of gut bacteria but also the predicted metabolic pathways of the microbiome, including those related to lipid metabolism and other biochemical processes. These changes may influence the host’s energy metabolism. PubMed Central
What Exactly Makes Up the Mediterranean Diet
The Mediterranean diet is typically characterized by:
- a high intake of vegetables, fruits, legumes, nuts, seeds, and whole grains,
- olive oil as the main source of fat,
- regular consumption of fish and other sources of unsaturated fatty acids,
- low intake of red meat, saturated fats, and highly processed foods,
- at most moderate alcohol consumption, most often in the form of red wine.
It is this combination of fiber, healthy fats, and polyphenols that creates an environment supporting the growth of microorganisms that produce metabolites beneficial for the intestinal lining.
The Mediterranean diet influences health not only through individual nutrients but also by creating favorable conditions for the gut microbiome. It promotes microbial diversity and metabolic activity, which may positively impact inflammatory processes and metabolic health.
It is not a quick fix or a universal recipe, but a long-term dietary pattern that makes sense both from a nutritional standpoint and for maintaining gut balance.