In any given moment, within a room of 100 people, 15 of them, on average, are experiencing depression or anxiety on a clinical level—ranking them in the top 10 for global burden of disease.1,2 Typically, treatment for depression and anxiety focuses on the brain. But while the brain is clearly involved with our mood and mood disorders, there’s also growing evidence to suggest we look somewhere else for the root cause and solution: our gut.
What’s your gut got to do with it?
As you know from reading my blog Meet Your Microbiome, your gut contains trillions of microbes, making up 10X your number of human cells and 100X your number of human genes.4 Collectively called your microbiome, this abundance of bacteria is linked to most systems and organs in your body, impacting many aspects of your health. In the last 10 years especially, science has explored how the gut microbiome interacts with your brain, and there’s SO much there it has been given a special name: the gut-brain axis.5 This isn’t JUST about the Vagus nerve, which connects the 2 organs. Now we’ve identified a whopping 50 additional pathways that connect the gut and the brain.5,6 While we don’t know everything about how and what they communicate, here’s what we DO know:
Almost ALL of the body’s serotonin (the happiness chemical) is made in your gut, not your brain. Only 5% of the “happy” and mood stabilizing neurochemical is made in your brain!4-6
People and animals with depression and anxiety:
Have LESS abundant microbiomes.6,10,12,16.17
Have MORE pro-inflammatory bacteria in their microbiome.6,10,12,16,17
Have LESS Bifidobacterium and Lacto-Bacillus bacteria in their microbiome (both commonly found in fermented foods.)11,15
People with a typical “Western” diet have a significant increased chance of developing depression and anxiety8-14
Animals with a “sterile” gut have significantly increased issues with brain cognition, memory, social issues and mood disorders, and they experience more stress, anxiety and depression.13 But there’s hope! When these mice’s guts were “colonized” with good bacteria, the issues resolved.14
So, what’s food got to do with it?
Given we’ve proven there is a meaningful connection between the gut and mood, it’s probably not surprising to learn that food plays a role (because, what you eat impacts your gut!) Here’s a summary of what we know about food and depression:
Foods like pizza, excessive wine, and ice cream actually make us feel worse when we’re feeling depressed.7 Which makes me wonder—what good is a comfort food if it doesn’t actually comfort?
A Mediterranean-style diet and the addition of fermented foods leads to massive improvements in mood and mental well-being.7-10,12,16,17
A prebiotic rich diet has been linked repeatedly to decreases in depressive-like behavior.18,19
Ingesting certain probiotics (like the most studied, lactobacillus) or eating fermented foods daily leads to big improvements in mood and increases in serotonin and dopamine levels for those that experience anxiety and depression.10,12,16,17 On average, the risk reduction was 30%—just from adding something to your diet!
So, what should I do about it?
In summary, among the variables that might protect us against mental health disorders and depression, diet, especially the impact of fermented foods, prebiotics, and probiotics, has emerged as a very strong candidate. The research has literally exploded around the subject—creating a whole new category of medicine called “PSYCHOBIOTICS,” or said differently—the ways fermented foods, prebiotics, and probiotics can literally change your psyche.17
I’m THRILLED this knowledge is becoming more mainstream and even finding its way to national publications like the New York Times. As a nutritionist who has dedicated her adult life to gut health, I am incredibly excited about what’s to come in the next decade in terms of dietary recommendation. My prediction? Way more kombucha and fermented foods!
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- DeRubeis RJ, Siegle GJ, Hollon SD. Cognitive therapy versus medication for depressions: treatment outcomes and neural mechanisms. Nat Rev Neurosci. 2008;9(10):788–96. [PMC free article][PubMed] [Google Scholar]
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- Smith PA. The tantalizing links between gut microbes and the brain. Nature. 2015;526:312–314. doi: 10.1038/526312a. [PubMed] [CrossRef] [Google Scholar]
- Huang TT, Lai JB, Du YL, Xu Y, Ruan LM, Hu SH. Current Understanding of Gut Microbiota in Mood Disorders: An Update of Human Studies. Front Genet. 2019;10:98. Published 2019 Feb 19. doi:10.3389/fgene.2019.00098 (referenced below too)
- Wagner, H. S., Ahlstrom, B., Redden, J. P., Vickers, Z., & Mann, T. (2014). The myth of comfort food. Health Psychology, 33(12), 1552–1557.
- Firth J, Marx W, Dash S, et al. The Effects of Dietary Improvement on Symptoms of Depression and Anxiety: A Meta-Analysis of Randomized Controlled Trials [published correction appears in Psychosom Med. 2020 Jun;82(5):536]
- Bear TLK, Dalziel JE, Coad J, Roy NC, Butts CA, Gopal PK. The Role of the Gut Microbiota in Dietary Interventions for Depression and Anxiety. Adv Nutr. 2020;11(4):890-907. doi:10.1093/advances/nmaa016
- Hidaka BH. Depression as a disease of modernity: explanations for increasing prevalence.J Affect Disord. 2012;140:205–214. doi: 10.1016/j.jad.2011.12.036.
- Oriach CS, Robertson RC, Stanton C, Cryan JF, Dinan TG. Food for thought: the role of nutrition in the microbiota-gut–brain axis. Clin Nutr Exp. 2016;6:25–38.
- Tillisch K, Labus J, Kilpatrick L, et al. Consumption of fermented milk product with probiotic modulates brain activity. Gastroenterology. 2013;144(7):1394-1401.e14014. doi:10.1053/j.gastro.2013.02.043
- Diaz Heijtz R, Wang S, Anuar F, Qian Y, Björkholm B, Samuelsson A, Hibberd ML, Forssberg H, Pettersson S. Normal gut microbiota modulates brain development and behavior. Proc Natl Acad Sci USA. 2011;108:3047–3052.
- Collins SM, Kassam Z, Bercik P. The adoptive transfer of behavioral phenotype via the intestinal microbiota: experimental evidence and clinical implications. Curr Opin Microbiol. 2013;16:240–245.
- Aizawa E, Tsuji H, Asahara T, Takahashi T, Teraishi T, Yoshida S, Ota M, Koga N, Hattori K, Kunugi H. Possible association of Bifidobacterium and Lactobacillus in the gut microbiota of patients with major depressive disorder. J Affect Disord. 2016;202:254–257.
- Barrett E, Ross RP, O’Toole PW, Fitzgerald GF, Stanton C. γ-Aminobutyric acid production by culturable bacteria from the human intestine. J Appl Microbiol. 2012;113:411–417.
- Dinan TG, Stanton C, Cryan JF. Psychobiotics: a novel class of psychotropic. Biol Psychiatry. 2013;74:720–726.
- Cenit MC, Sanz Y, Codoñer-Franch P. Influence of gut microbiota on neuropsychiatric disorders. World J Gastroenterol. 2017;23(30):5486-5498. doi:10.3748/wjg.v23.i30.5486)
- Hughes C, Davoodi-Semiromi Y, Colee JC, Culpepper T, Dahl WJ, Mai V, Christman MC, Langkamp-Henken B. Galactooligosaccharide supplementation reduces stress-induced gastrointestinal dysfunction and days of cold or flu: a randomized, double-blind, controlled trial in healthy university students. Am J Clin Nutr. 2011;93:1305–1311.
Today's blog is written by our very own Daina Trout, MS, MPH