A new study shows how gut bacteria might explain the much-touted benefits of the “Mediterranean diet.”
The Mediterranean diet is a broad and loose term that generally alludes to the food eaten in Greece, southern Italy, and parts of Spain. Unfortunately, this doesn't mean eating a pepperoni pizza and a bottle of wine every night, but refers to a diet rich in vegetables, fruits, legumes, nuts, beans, cereals, grains, fish, and unsaturated fats, such as olive oil. Eating these kinds of food on a regular basis has been linked to all kinds of positive health effects, especially for the heart and cardiovascular system.
In a new study, reported this week in the journal Nature Medicine, scientists argue some of the health benefits of the Mediterranean diet may actually lie in the way the diet interacts with our gut microbiome.
The trillions of bacteria, viruses, protozoa, and fungi that live in the human intestinal tract are much more than passive lodgers. They are also known to play a central role in our bodies’ metabolism, nutrition, and immune function, which can go on to influence our wider health and even our mood.
Researchers at Harvard T.H. Chan School of Public Health looked at the health and gut microbiome of over 300 healthy men. Along with taking poop samples every six months for two years, they were also asked to fill out a questionnaire about their diet. They found that those who adhered to a Mediterranean diet had a notably different make-up of gut bacteria, namely high concentrations of major dietary fiber metabolizers, such as Faecalibacterium prausnitzii and Bacteroides cellulosilyticus.
Furthermore, the presence of one bacteria species, known as Prevotella copri, was found to have an especially interesting link to cardiovascular health. The researchers found that people with decreased levels of P. copri appear to have experienced more of the positive effects of the Mediterranean diet on cardiometabolic disease. In other words, people with little or no P. copri reap more of the benefits of the Mediterranean diet.
The researchers are not certain why P. copri appears to have this link, but they have a few ideas. Firstly, it could simply be that unhealthier diets, which increase the risk of cardiovascular, tend to foster the growth of P. copri. Alternatively, individuals who do not carry P. copri in the gut microbiome may metabolize components of the Mediterranean diet more efficiently and effectively, obtaining more of its cardioprotective effects.
However, the exact nature of this relationship remains speculation for now. The researchers point out that their study was merely observational and they’re limited in their ability to understand the underlying mechanism behind the patterns they observed. They also note that the interactions between the microbiome and diet is an immensely fiddly business. For example, many different subclades of P. copri can be found in different populations across the world, most likely due to diet and lifestyle differences, and not all clades may interact with the Mediterranean diet in the way seen here.
That said, this research is a good example of how new research is shedding light onto the mechanisms that underlie the relationship between the microorganisms that live within us and disease.