Diet is a key factor for good health. To understand the role of the gut microbiota in this relationship, the Microbiome Research group at Vall d'Hebron Research Institute (VHIR) has led a study to analyse the microbiota depending on diet, lifestyle and place of residence. The study, carried out with people from different regions of Spain, was recently published in the journal npj Biofilms and Microbiomes.

Microbiota can be influenced by numerous personal, lifestyle and environmental factors. One of the aims of VHIR's work has been to understand how national nutritional recommendations can influence the microbiota and, therefore, health. “It is one of the largest studies on the composition and function of the gut microbiota depending on diet and lifestyle in the Spanish population”, says Dr Chaysavanh Manichanh, head of the Microbiome Research group at VHIR and researcher in the Liver and Digestive Diseases area of CIBER (CIBEREHD).

The study involved 1,001 healthy participants from all the autonomous communities of Spain, divided into four regions: Mediterranean, north, interior, and islands. Everyone completed questionnaires with personal, place of residence, and dietary data at the start of the study, six and 12 months later. In total, more than 2,000 diet profiles were collected from all participants. In addition, stool samples were collected to analyse the gut microbiota.

In total, the microbiome of 500 of these healthy participants was analysed and compared with that of 321 other people with inflammatory bowel disease (IBD). The team has previously studied this pathology and has shown that there is an alteration in the composition and diversity of the microbiota present in the gut (dysbiosis). “This methodology allows us to know how similar the microbiota of a healthy person, depending on their diet, is to that of a person with IBD”, explains Zaida Soler, pre-doctoral researcher in the Microbiome Research group at VHIR.

The results of the analysis showed that having a healthy diet, according to national recommendations, is associated with a better microbiome. For example, diets rich in nuts, fruits and vegetables were associated with greater microbiota diversity and less IBD-associated dysbiosis. In contrast, sweets, white bread or soft drinks were associated with less diversity in the microbiota and therefore more similarity to IBD.

Furthermore, diet was identified as affecting not only the diversity, but also the composition of the microbiota. A healthy diet is associated with bacteria related to the maintenance of the intestinal barrier, and also with bacteria with an antioxidant effect.

Differences according to age, gender or place of residence

In order to understand the differences according to personal characteristics, the relationship was studied according to age or gender. It was observed that, in general, older people have a better diet (more consumption of wholegrain bread, nuts, fruits...). On the other hand, men consume more precooked foods and alcoholic beverages and less wholegrain bread or vegetables than women. This was reflected in a more or less altered microbiota.

Depending on the place of residence, differences were also identified. For example, areas in the Spanish interior showed a healthier dietary pattern, especially with a higher consumption of legumes, which have many health benefits because they are rich in nutrients and compounds such as protein, fibre, vitamins and minerals.

"However, we must bear in mind that the microbiota is not only diet-dependent, but multifactorial. To study it, we have to look at all these factors”, explains Dr Manichanh.

A project with citizen involvement

This study was possible thanks to the participation of a thousand participants, who played a major role in the research and in the collection of samples. To facilitate the collection of data, the research team created a website through which people could fill in the form about their personal details and diet.

In addition, the website offers resources to explain the importance of the project and the impact of the research, to create a link between the participants and the scientific community. "This website makes information about the project available to everyone and, in addition, each participant has been able to privately access data about their food consumption and microbiota composition. It is a way to make visible the important role of citizens in science”, concludes Dr Manichanh.