Mycobacterium vaccae is a non-pathogenic bacterium found naturally in soil. Its name comes from the Latin word “vacca” (cow), as the first strain was cultured from cow dung. This bacterium has drawn scientific and public attention due to its potential effects on human health, making it a subject of ongoing research.
The Immune System Connection
The “Old Friends” or hygiene hypothesis suggests that reduced exposure to a diverse range of microorganisms, including Mycobacterium vaccae, may contribute to inflammatory and autoimmune conditions in modern societies. This theory proposes that our immune systems, accustomed to constant microbial interaction, now lack the necessary “training” to maintain a balanced response. A lack of early life exposure can lead to an exaggerated inflammatory response.
Exposure to M. vaccae can help regulate the immune system, fostering a more balanced inflammatory response. Specifically, this bacterium stimulates regulatory T-cells (Tregs), which are specialized immune cells that help suppress excessive inflammation. By promoting the production of anti-inflammatory cytokines, M. vaccae may help mitigate inflammation, a factor linked to various chronic disorders. One lipid found in M. vaccae, 10(Z)-hexadecenoic acid, can inhibit pathways that drive inflammation within stimulated immune cells.
Influence on Mood and Brain Health
Mycobacterium vaccae impacts mood and brain health, largely through its interaction with the immune system and the gut-brain axis. When immune cells are activated by M. vaccae, they trigger serotonin release in the brain, a neurotransmitter associated with mood regulation. Studies in mice show exposure to this bacterium increases serotonin production in brain areas that modulate anxiety and depression, such as the prefrontal cortex. This mechanism may explain observed antidepressant-like effects.
The gut-brain axis is a bidirectional communication pathway between the gut microbiome and the central nervous system. M. vaccae, as a soil microbe, influences this axis by promoting an anti-inflammatory state in the brain. Research indicates M. vaccae can reduce levels of stress-induced proteins and increase receptors that help maintain brain immune cells in an anti-inflammatory state. This modulation of brain inflammation is thought to underlie its potential to reduce anxiety and promote stress resilience.
Current Research and Therapeutic Potential
Research into Mycobacterium vaccae is ongoing, with findings from animal and early human studies. In mice, injections of M. vaccae have been shown to increase serotonin levels and decrease anxiety-like behaviors, while oral administration improved maze navigation and reduced anxiety. These animal models suggest a potential for preventing stress-related psychiatric disorders.
Beyond mood disorders, M. vaccae is being explored for its broader therapeutic potential. It has been investigated as an adjuvant in tuberculosis treatment, showing improved sputum conversion and radiological assessment in some meta-analyses. There is also interest in its use for autoimmune diseases and as a potential adjunct to improve outcomes in cancer treatment, though early trials for cancer did not consistently show improved survival rates. However, M. vaccae is currently in the research phase and is not available as a commercial supplement or an approved medical treatment.
Natural Exposure and Safety
People are naturally exposed to Mycobacterium vaccae through outdoor activities like gardening, farming, and spending time in natural environments where soil is present. Contact can happen through the skin or by inhaling soil particles in the air.
Mycobacterium vaccae is a non-pathogenic bacterium, meaning it does not typically cause disease in healthy individuals. While rare instances of infection have been reported, these usually occur in individuals with compromised immune systems or underlying health conditions. For the general population, natural exposure to M. vaccae is considered safe.