Share on PinterestHow might a Mediterranean diet help protect brain health? A new study in rats sheds more light on the potential mechanisms. Image credit: Elena Noviello/Getty Images.

• Studies increasingly show a link between diet and both physical and mental health.
• Diets rich in plants and whole grains may decrease the risk of several health conditions, and could also improve cognition and decrease risk of neurodegenerative diseases, such as dementia.
• Now, a study has shown that the Mediterranean diet, which emphasizes plants, whole grains and healthy fats, is associated with improved memory and learning in young rats.
• The authors suggest that similar dietary changes could have cognitive benefits for children and adolescents.

According to the World Health Organization (WHO)Trusted Source, following a healthy diet throughout life can not only protect against malnutrition, but can also reduce the risk of noncommunicable diseases, such as diabetes, heart disease, stroke and cancer.

The WHO advises that a healthy diet includes:

• fruit, vegetables, nuts, and whole grains
• less than 10%, and ideally less than 5%, of total energy intake from free sugars, such as found in honey, syrups, fruit juices, soft drinks, and ready-prepared foods,
• less than 30% of total intake from fats, most of which should be unsaturated fats from fish and vegetable oils, rather than animal fats
• less than 5 grams (g) of salt a day.

Increasingly, studies are suggesting that a healthy diet may also reduce the risk of cognitive disorders, such as dementia.

Diet could influence brain health

The Mediterranean diet and variations of it, which emphasize intake of fruits, vegetables, whole grains and olive oil, while limiting meat, dairy and ultra processed foods, may be particularly beneficial for brain health.

There are few studies that have investigated the cognitive effects of a Mediterranean diet in younger people, but one, from Mexico, showed academic and cognitive benefits of a Mediterranean-style diet when compared with a typical Western diet.

Now, a study in rats, has tested whether such benefits may be due to changes in the gut microbiota that result from eating a Mediterranean, rather than a Western diet.

The study, published in Gut Microbes Reports, suggests that not only did the Mediterranean diet change gut microbiota and improve serum lipid levels, it also improved memory and cognition.

Scott Kaiser, MD, a board-certified geriatrician at Providence Saint John’s Health Center in Santa Monica, CA, who was not involved in this study, told Medical News Today:

“A growing body of evidence clearly supports a strong correlation between diet and brain health. While this study, and other related cornerstone studies in this field, may not be designed to specifically establish causation there are many clear causal pathways and plausible biological mechanisms that support the likelihood that various diets and nutritional factors may either be protective of our brain health or accelerate cognitive decline and otherwise impact our mental well-being.”

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Changes in gut microbiota tied to memory improvements

At the start of the 20-week study, the rats were 10 weeks old. Studies show that laboratory rats become sexually mature at 6 weeks, and in adulthood, one month is equivalent to approximately 3 years of human life, so the developmental stage of the rats in this study equates to people from around 8 to 20.

At the start, the researchers randomly assigned the 20 rats to either a Western diet, containing 15% protein, 50% carbohydrate, and 35% fat (primarily butter), or a Mediterranean diet, with 12% protein, 45% carbohydrate, and 43% fat (primarily olive oil).

The Mediterranean diet contained more than twice as much fiber (63.4 grams per kilogram [ g/kg]) as the Western diet (27.9 g/kg).

During the study, researchers monitored the rats’ body weight and food consumption to ensure that energy intake was similar in the 2 groups. They also took fecal samples for analysis at the beginning of the study and after 14 weeks on the diets, when the rats began a series of behavioral tests.

They detected widespread changes in the gut microbiota of the Mediterranean diet rats. These rats showed increases in four types of bacteria and decreases in five other types compared with those on the Western diet.

In behavioral tests, Mediterranean diet rats showed better cognitive flexibility and improvement in aspects of spatial reference and working memory. These improvements correlated with higher levels of Candidatus saccharimonas and lower levels of Bifidobacterium in their gut microbiota.

The researchers suggest that this change in microbiota could be responsible for the improved cognitive function of the rats on the Mediterranean diet.

Kelsey Costa, MS, RDN, a registered dietitian nutritionist and founder of Dietitian Insights, who was not involved in this study, agreed with this hypothesis, telling MNT that “this study adds to the growing body of evidence for a potential link between modified microbiota and improved memory function.”

“The gut-brain axis allows two-way communication between the gut and the brain, with the gut microbiome potentially influencing cognitive functions like attention, perception, and memory. Diet-modulated gut microbiota might impact cognition, in particular, by disrupting immune function,” she explained.

Do these findings apply to humans?

Most research into the relationship between microbiota and cognitive function has looked at neurodegenerative diseases, such as dementiaTrusted Source, but this study suggests that modifying microbiota by improving diet could also improve cognitive function in adolescence.

“While causal evidence has not been established, observational research has suggested a link between diet quality and cognitive performance in children and adolescents.”

– Kelsey Costa, MS, RDN

The authors emphasize that further research is needed to determine whether there is a causal relationship between diet quality and cognition.

Costa agreed, noting that: “Overall, encouraging a healthy eating pattern like the Mediterranean-style diet from an early age may have long-lasting benefits for cognitive function in children and adolescents. But, more research is needed to fully understand the mechanisms and apply these results to human populations.”

Whether the Mediterranean diet can improve cognition or not, there is general recognition that following this type of diet has health benefits.

Molly Rapozo, RDN, a registered dietician nutritionist and senior nutrition and health educator at Pacific Neuroscience Institute in Santa Monica, CA, also not involved in this study, shared the following dietary advice for those concerned about brain health:

“We can modify our diets to preserve and improve brain health by including vegetables, fruit, starches such as whole grains, legumes, and potatoes; as well as lean protein, fatty fish, and plant fats such as nuts, seeds, avocado, olives, and olive oil. Eat less highly processed snack foods, fatty meats including bacon and sausage, sugar, and other refined carbohydrates.”