Mediterranean diet: how beneficial gut bacteria improve memory

Source: Rebecca J. Solch-Ottaiano et al, "Comparison between two divergent diets, Mediterranean and Western, on gut microbiota and cognitive function in young sprague dawley rats," Gut Microbes Reports (2024). DOI: 10.1080/29933935.2024.2439490

As part of the experiment, the experts fed the rats food that mimicked the Mediterranean diet for 14 weeks. This diet included olive oil, fish and plenty of fibre.

The other control group received a traditional "Western" diet rich in saturated fats. It turned out that the rats on the "Mediterranean" diet had an increase in four types of "beneficial" bacteria and a decrease in five others, while in the "Western" group, the balance shifted towards bacteria that contribute to memory impairment and increased levels of "bad" LDL cholesterol.

To test the effect of bacterial changes on the brain, the researchers conducted maze tests assessing the memory and learning performance of the rats. The animals on the Mediterranean diet performed much better on the tasks and showed better "cognitive flexibility", i.e. the ability to adapt quickly to new conditions. Higher levels of bacteria in the Candidatus Saccharimonas group were associated with better memory performance, while higher levels of Bifidobacterium in the "Western" group were associated with worse results.

From a human health perspective, it is particularly interesting that the study was conducted on young rats, close in age to 18-year-old humans. Because the brain is still actively developing during this period, the authors suggest that a similar diet in adolescents and young adults may promote higher levels of cognitive ability, as well as reduce the risk of cognitive impairment in the future.

"Our findings suggest that the effects of the Mediterranean diet are not only related to the benefits of the food itself, but also to how it changes the gut microflora," emphasises the study's lead author, Dr Rebecca Solch-Ottaiano.

According to Professor Demetrius M. Maraganore, it is important that future human studies confirm these findings and help to better understand exactly how the balance of bacteria in the gut interacts with the brain at a young age.

To follow a Mediterranean diet, experts recommend using olive oil more often, eating more vegetables, fruit, fish and whole grain products, while limiting red meat, saturated fats and favouring a variety of fibre sources.