The link between diet and mental health is well established and you may already be making the effort to eat mood and mind-boosting foods. But there is another consideration when eating for your mental health—microbes. Specifically, bacteria in your gut.
For years, scientists thought that the brain was at the helm of your thoughts and feelings through a top-down approach of operation, where it would control and guide every process in the body. In recent history, we've learned that microbes in our gut, especially the large intestine, are also in constant communication with the brain via the central nervous system. Emerging evidence is forging a stronger link between your micro biota and behaviors, anxiety, stress, and depression.(1) Though much remains to discover, here are three ways gut microbes may be impacting your mental health and vice versa:
Depresssion
Recent studies have found altered gut bacteria in people with mental health problems. One study found higher levels of Proteobacter and Bacteroidetes in a sample of patients with depression. These bacteria are linked with higher levels of inflammation. Interestingly, higher levels of isovaleric acid were also found in these patients, which is a neurotransmitter that competes with the relaxing amino acid GABA.(2)
A large retrospective study looking at 200,000 people with depression in the UK also found that higher antibiotic usage is linked to an increased risk for depression and anxiety. With more studies like these coming to light, the importance of keeping your gut bacteria in balance will become a critical point in mental health.(3)
Stress
Stress increases intestinal permeability and inflammation. A Norwegian study of soldiers who endured challenging and stressful situations for four days had significant changes to their guts that increased the leakiness of their guts and systemic inflammation. Increased permeability of the gut allows inflammatory bacterial byproducts to enter the bloodstream where they can circulate to the rest of the body and trigger inflammatory pathways of the immune system. If managing stress isn't front of mind yet, make sure to incorporate easy daily stress management habits to keep your gut-brain axis in balance.(4)
Alzheimer's
Alzheimer's is a growing problem in the US where it currently ranks as the sixth leading cause of death. The disease robs people of their memories and mental faculties as the nerve cells slowly die through the progression of the disease. Much research is still needed to better understand all the factors affecting Alzheimer's progression, but chronic low-grade inflammation (the kind brought about by chronic stress) is a significant risk factor. Lipopolysaccharide (LPS) is a molecule found in higher amounts in Alzheimer's patients. This molecule is found in many bacteria and can trigger inflammation in the body.
The strongest link between Alzheimer's and gut bacteria can be found in studies using mice, where microbial sterile mice had 70% less likelihood of brain pathology and neuroinflammation, but had an increased likelihood of developing brain problems when they had a gut biome transplant from mice with brain pathology.
Supporting A Balanced Gut
Researchers at Rush University in Chicago have created a new diet that is specifically designed to support mental health. It is appropriately called the MIND diet. The MIND diet focuses on ten foods that reduce brain pathology, like Alzheimer's.(5) The diet emphasizes eating dark leafy greens, vegetables, nuts and seeds, oils, berries, whole grains, and more. Learn more at
https://www.rush.edu/news/mind-diet.
Probiotics are increasing in popularity as more people set out to supplement and support a healthy gut biome. Studies suggest that probiotics may help reduce gut permeability, oxidative stress and inflammation.(6) In animal studies probiotics have also been linked to decreased risk of anxiety, depression, and stress and human studies are also showing benefits to participants.(7) While eating a diet rich in probiotic foods like kimchi, sauerkraut and kefir are great ways to support an optimal gut biome, functional foods that incorporate pre- and probiotics can also offer a convenient solution to a healthy gut-brain axis.
References
- Foster JA, McVey Neufeld KA. Gut-brain axis: how the microbiome influences anxiety and depression. Trends Neurosci. 2013 May;36(5):305-12. doi: 10.1016/j.tins.2013.01.005. Epub 2013 Feb 4. PMID: 23384445. https://pubmed.ncbi.nlm.nih.gov/23384445/ (accessed February 2021).
- Jiang H, Ling Z, Zhang Y, et al. Altered fecal microbiota composition in patients with major depressive disorder. Brain, Behavior, and Immunity. Volume 48, 2015, Pages 186-194, ISSN 0889-1591. https://doi.org/10.1016/j.bbi.2015.03.016 (accessed February 2021).
- Lurie I, Yang YX, Haynes K, Mamtani R, Boursi B. Antibiotic exposure and the risk for depression, anxiety, or psychosis: a nested case-control study. J Clin Psychiatry. 2015 Nov;76(11):1522-8. doi: 10.4088/JCP.15m09961. PMID: 26580313. https://pubmed.ncbi.nlm.nih.gov/26580313/ (accessed February 2021).
- Karl JP, Margolis LM, Madslien EH, et al. Changes in intestinal microbiota composition and metabolism coincide with increased intestinal permeability in young adults under prolonged physiological stress. APSselect 2017 4:5, G559-G571. https://journals.physiology.org/doi/full/10.1152/ajpgi.00066.2017%40apsselect.2017.4.issue-5 (accessed February 2021).
- Morris MC, Tangney CC, Wang Y, et al. MIND diet associated with reduced incidence of Alzheimer's disease. Alzheimers Dement. 2015 Sep;11(9):1007-14. doi: 10.1016/j.jalz.2014.11.009. https://pubmed.ncbi.nlm.nih.gov/25681666/#:~:text=Introduction%3A%20In%20a%20previous%20study,incident%20Alzheimer's%20disease%20(AD). (accessed February 2021).
- Rao RK, Samak G. Protection and Restitution of Gut Barrier by Probiotics: Nutritional and Clinical Implications. Curr Nutr Food Sci. 2013;9(2):99-107. doi:10.2174/1573401311309020004 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3864899/ (accessed February 2021).
- Messaoudi M, Lalonde R, Violle N, et al. Assessment of psychotropic-like properties of a probiotic formulation (Lactobacillus helveticus R0052 and Bifidobacterium longum R0175) in rats and human subjects. Br J Nutr. 2011;105(5):755-764. doi:10.1017/S0007114510004319 https://pubmed.ncbi.nlm.nih.gov/20974015/ (accessed February 2021).
