Fermented foods are associated with numerous mental health benefits, positively influencing gut microbiome balance and, as a result, brain function (gut-brain axis). Through the fermentation process, these foods become rich sources of probiotics and beneficial metabolites known for their ability to affect neurotransmitters, inflammation, and oxidative stress—all critical factors in brain health. A new study once again confirms the benefits of these products.

The gut-brain axis is linked to a variety of cognitive and emotional functions, including memory, thinking, anxiety, depression and general health. A new study published in the journal Neuroscience & Behavioral Reviews examined different types of fermented foods, the fermentation processes involved, and how they may affect the gut microbiome’s interaction with the brain (gut-brain axis).

In Romania, two particularly popular local fermented foods are borscht and sauerkraut. Below is a list of other such foods and beverages:

• Yogurt/kefir is a fermented milk product obtained by fermenting milk with probiotic bacteria;
• Kimchi is a traditional Korean dish, usually prepared from sauerkraut and other vegetables;
• Kombucha is a fermented drink made from sweet tea, enriched with bacteria and yeast;
• Misu – fermented soybean and/or barley paste used in Japanese cuisine;
• Tempeh is an Indonesian fermented soy product used as a meat substitute in many vegetarian recipes.

According to the study, fermented foods were observed to directly affect the endocrine system, which regulates hormones responsible for appetite and digestion, such as ghrelin, neuropeptide-Y, GLP-1 (glucagon-like peptide-1), and serotonin. These fermented foods are rich in prebiotics and probiotics recognized for their ability to influence gut health. A specific result of fermentation is increased production of GLP-1, a hormone that plays an important role in satiety regulation and blood sugar control.

However, there are still aspects of how fermented foods affect appetite and hunger that require further research to be fully understood. Human studies of fermented milk products have produced mixed results regarding cognitive health, while observational studies have linked consumption of fermented milk products to changes in gut health and reduced anxiety.

Connection between gut and brain

“We know from previous research that there is a well-established connection between the gut and the brain (the gut-brain axis) and that this directly links diet to brain function and behavior, depending on the health of the microbiota (the community of bacteria in the gut) ,” said Dr. Nicole Avena, an expert in nutrition and neurology, emphasizing that this review sheds light on the history of fermented foods and the physiology of their recognition as superfoods that benefit both gut and brain health. The human gut is home to a variety of bacteria, Avena explains.

What makes each person’s microbiome unique is the influence of a diverse combination of factors, from the mother’s health before birth to the current environment in which we live. The importance of nutrition in maintaining gut health is critical as it is a tangible way to diversify and strengthen your gut flora. The connection between the gut and the brain is critical to mental health because it depends on the health and diversity of the microbiome. The less varied the diet, the greater the risk to mental health and brain health. These bacteria are known to be necessary for the processes of digestion, absorption and production of nutrients, which can directly affect the mental state.

The brain and gut are connected by many neural and circulatory pathways, explained Dr. William Lee, MD, and New York Times bestselling author of Eat to Beat Diet: Burn Fat, Boost Your Metabolism, and Live Longer “.

“Substances produced in the gut by bacteria can travel or send signals to all major nerves, such as the vagus nerve, directly to the brain, triggering various brain activities that can alter mood, behavior, memory and cognition,” he noted. specialist. On the other hand, substances produced in the brain can travel along nerves that start from the brain and extend into the intestines like electrical wires. These chemical signals can affect the balance and functioning of the bacterial ecosystem in the gut.

From a circulatory perspective, microbes in the gut can secrete substances that are then absorbed into the bloodstream and transported directly to the brain. Similarly, chemical signals generated by brain cells can enter the bloodstream and then be transported to the gut, affecting the gut microbiome. “There are many compelling correlations showing that dysbacteriosis, or an abnormal composition of the gut microbiome, is associated with depression, anxiety, dementia, Parkinson’s disease, and other neurodegenerative disorders,” said Dr. William Lee.

What is a psychobiotic diet?

Fermented foods are a rich source of biologically active substances such as polyphenols and dietary fiber (prebiotics), as well as healthy bacteria called probiotics and metabolites produced by fermentation called postbiotics. These essential elements of fermented foods significantly contribute to the health of the gut microbiome. They act by feeding healthy bacteria in the gut, thus stimulating their activity in the gut-brain system, or by directly influencing the composition of the gut microbiome.

The overall effect of regular consumption of fermented foods is to help create and maintain a healthy gut ecosystem that has the ability to activate gut-brain communication pathways. Dr. John F. Cryan, coordinator of the Department of Anatomy and Neurosciences at University College Cork in Ireland, first coined the term “psychobiotic diet” in 2013 to describe dietary interventions designed to influence the gut microbiota and positively impact mental health. .

In 2023, a study he conducted with his team examined the effects of certain types of food—prebiotics and fermented foods (probiotics)—on the connection between the brain and the gut. 45 healthy adults between the ages of 18 and 59 were recruited on a low-fiber diet. Of these, 24 were included in the psychobiotic diet group and 21 in the control group. The study lasted four weeks. Before, during and at the end of the study, the composition of the microbiota in the feces of the participants was analyzed.

Stress level, general state of health and diet were also assessed using standard questionnaires. An analysis of the metabolic profile of plasma, urine, and feces samples was also performed.

Participants in the psychobiotic diet group consumed the following foods during the study:

• 6-8 daily portions of fruits and vegetables with a high content of prebiotic dietary fibers, such as onions, leeks, cabbage, apples, bananas;
• 5-8 daily portions of cereals;
• 2-3 daily servings of fermented foods, including sauerkraut, pickles, kimchi, kefir and koumiss;
• 3-4 servings of legumes per week, such as beans, peas and lentils.

At the same time, participants of the control group were recommended to follow a diet according to the food pyramid. At the end of the four-week study, the Irish researchers observed a 32% reduction in the level of stress perceived by participants in the psychobiotic diet group. In addition, minor changes in gut bacterial composition were observed, but significant changes in specific fecal lipids and urinary tryptophan metabolites were found.

Two categories of fermented foods that are good for the brain

The researchers also found that there are two categories of fermented foods that appear to have significant positive effects on brain health: sugar-based and vegetable-based fermented foods. Fermented vegetable products include a wide range of options such as:

• Salting of natural fermentation,
• kimchi,
• miso,
• tempo,
• Tea tea.

Regarding sugars, it is important to note that during microbial fermentation, dietary polysaccharides are converted into fermentable sugars such as glucose (from cellulose), xylose, arabinose, galactose, and mannose. Although sugar-based foods are often demonized, fermented sugar converts raw sugar into a variety of beneficial metabolites. So any fermented food that contains a source of sugar, such as the lactose in milk that turns into yogurt, can benefit brain health.

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