Food fermentation is an ancient culinary practice that improves the palatability and nutritional value of foods while also having preservative and medicinal functions. Fermented foods and beverages such as sauerkraut, kimchi, yogurt, and kefir are rich in probiotic bacteria such as Lactobacillus and Bifidobacteria and have recently experienced a resurgence in popularity due to increased awareness of the importance of the microbiome and gut health. A growing body of research indicates that the gut microbiome plays a key role in mental health. The consumption of fermented foods may, therefore, be a useful strategy for optimizing mental health. Read on to learn about how probiotics associated with fermented foods may influence brain function and optimize mental and emotional health.
Fermented foods: An ancient antidepressant
Our Paleolithic ancestors had plenty of opportunities to consume foods that had been naturally subjected to microbial fermentation, such as honey, fruits, and berries. Over time, our ancestors came to recognize that fermented foods had beneficial effects on the body, including mental function. This marked the beginning of the ancestral practice of intentional food fermentation. Chemical analyses of food residues in pottery from Neolithic Central America indicate that fermented cacao beverages were being made prior to 1000 B.C. (1) We now know that cacao has neuroprotective effects, enhances cognitive function, and reduces stress. (2)(3) Research also indicates that fermented beverages made of rice, honey, and fruit were being produced in China as far back as 9,000 years ago, around the same time that beer and wine were being produced in the Middle East. (4) Clearly, the roots of our relationship with fermented foods extend far back into human history.
In the present day, scientific research has revealed that probiotic bacteria present in fermented foods have beneficial effects on mental health. (5) Currently, rates of mental health disorders are at an all-time high. Conversely, poor mental health was an anomaly in ancestral communities eating traditional diets, which included plenty of fermented foods. Depression, anxiety, and other psychiatric conditions are “diseases of modernity,” influenced by our modern diet and lifestyle. (6) Could a return to ancestral fermented food consumption be an effective intervention for mental health disorders? The research certainly indicates this it could!
Gut health is compromised in people with mental health disorders
The intestinal wall consists of cells connected by proteins; together these form epithelial tight junctions. Epithelial tight junctions are responsible for regulating intestinal permeability, which controls what can and cannot escape from the intestine into the systemic circulation. When tight junctions are damaged by things such as pathogenic bacteria or certain food chemicals, intestinal permeability is increased and toxins and food proteins can escape from the intestine into the bloodstream, initiating an inflammatory response. This inflammatory response has been linked to depression (7), schizophrenia (8), autism spectrum disorder (9), and anorexia nervosa. (10) A healthy gut microbiome is essential for ensuring preventing excessive intestinal permeability. The consumption of fermented foods, rich in beneficial bacteria, can help replenish the gut microbiome and reduce intestinal permeability. Over time, this may restore normal mental health.
Beneficial bacteria in fermented foods improve mental health
A growing body of research indicates that beneficial bacteria (aka probiotics), which can be found in fermented foods, have a wide range of positive effects on mental health. Here are some of the most important findings:
- Consumption of a fermented beverage containing Lactobacillus casei for just three weeks was found to improve mood and cognition in a large group of adults with digestive complaints. (11)
- Supplementation with Lactobacillus helveticus and Bifidobacterium longum, commonly found in fermented foods, improved depression, anxiety, anger, and anxiety in adults. (12)
- One-month consumption of a fermented dairy product containing Bifidobacterium animalis subsp. lactis, Streptococcus thermophilus, L. bulgaricus, and L. lactis subsp. lactis was found via fMRI to influence regions of the brain involved in the central processing of emotion. (13)
- Red wine has been shown to increase Bifidobacterium levels, which lower a type of pro-inflammatory bacterial metabolite, LPS, that has been implicated in mental health disorders. (14)
- Fermented buckwheat sprouts and lentils have been found to be a rich source of GABA, a calming neurotransmitter that is involved in the regulation of anxiety. (15)(16)
- Lactobacillus pentosus, derived from kimchi, improves mental function and increases BDNF, a protein that supports normal brain function. (17)
Mechanisms of action
Probiotics appear to influence mental health by sending signals through the gut-brain-microbiome axis, which connects the body’s central nervous system (CNS), which houses the brain and spinal cord, with the enteric nervous system (ENS) of the gastrointestinal tract. (18) This axis coordinates bidirectional neural, hormonal, and immunological communication between the gut and brain. The microbiome serves as a node along this axis, producing metabolites that relay messages to both organs. Dysbiosis causes dysregulation of the gut-brain-microbiome axis. Conversely, restoration of a healthy microbiome with probiotics and fermented foods can normal the axis and promote optimal mental health.
Beneficial microbes in fermented foods may also promote mental health by increasing the bioavailability of vitamins and minerals that regulate mood, such as B vitamins, vitamin D, magnesium, and zinc. (19)(20)(21) Finally, microbial fermentation of foods enhances levels of antioxidants and other bioactive compounds, such as GABA (a calming neurotransmitter) that reduce inflammation, which has been implicated in poor mental health and exert antidepressant activity. (22)
While more clinical research would be helpful in understanding how probiotics and fermented foods impact mental health, I think the rich ancestral human history of fermented food consumption is reason enough to begin incorporating more fermented foods into your diet. Fortunately, fermented foods have gone [almost] mainstream, so there are a wide variety of products to choose from in grocery and health food stores. Give sauerkraut, kimchi, kefir, kvass, or yogurt (just to name a few products) a try – you may just find that these fermented foods improve your mood!