Fermented foods are highly beneficial to your health. However, the underlying practices regarding human consumption (the Paleolithic tradition of eating them) and the new scientific developments regarding just how these foods are bioactive – are two vastly underrepresented areas of knowledge. I hope to cover both areas and explain just why our ancestors instinctually sought out fermented foods, and what we now know about the exact scientific mechanisms that underlie their function in the human body, as well as the brain.
Firstly, our Paleolithic ancestors consumed honey, fruits or berries, and their juices, which were unknowingly subjected to natural microbial fermentation.1 It didn’t take salient scientific literature to suggest these fermented foods were optimal for their health.2 Fermented foods have mentally stimulating properties, analgesic properties, sedating properties, and many other positive functions.3 Interestingly, the shift away from traditional diets has been marked with not only changes in gut microflora, but also an increase in depression and negative mental health conditions.4
As the authors of this study note, chronic diseases, which are growing in prevalence, largely arise from a mismatch of our microbiome, which did exceedingly well in past environments, and modern day living.5 Our modern world is overfed, malnourished, sedentary, sleeping less than ever, and socially isolated.6 This not only leads to depression, but to metabolic syndrome, as well – which furthers depression.7 How can fermented foods help to combat the modern pandemic of metabolic syndrome, obesity, and depression?
This is a good question, and one with many answers.8 Mechanistically, their role in the production of specific neurotransmitters is important, and one possible answer to the proposed question.9 As researchers have noted, micronutrients play a role in the synthesis of neurotransmitters.10 A Western diet provokes not only a systemic inflammatory state, but also an altered mood (via intestinal permeability) and can even interfere in microbe-to-brain signaling pathways.11, 12 In fact, researchers have even found metabolic syndrome in the brain.13
This study provided mechanistic evidence that dietary habits can interact with brain functions. Of course, another reason to consume a Paleo Diet rich in fermented foods, and lower in sugar, is the long-term detrimental effects of high-sugar diets on cognitive function.14
Historically, traditional diets are correlated with lower levels of anxiety and depression. Plainly stated in one study’s conclusion, “those with better quality diets were less likely to be depressed, whereas a higher intake of processed and unhealthy foods was associated with increased anxiety.”15 What do almost all traditional diets have in common? They contain fermented foods. In fact, fermented foods and beverages can comprise anywhere between 5-40% of the human diet in some populations.16 In addition, important groups of gut bacteria, often considered markers of a healthy gut, are inversely associated with obesity.17, 18, 19
Furthermore, in mice, the absence of toll-like receptor 5 alters the gut microbiota – leading to more food intake, insulin resistance, and obesity.20 Eating fermented foods helps to favorably effect the composition of the gut microbiota.21 In addition, epidemiological studies have shown that consumption of cabbage and sauerkraut is connected with a significant reduction of breast cancer occurrences.22
So, how did our Paleolithic ancestors know that fermented foods would be beneficial? This answer remains unclear, even though traditions were passed down from generation to generation. Fermentation of food increases beneficial flora, like lactic acid bacteria.23 While our ancestors likely didn’t know this, they still used fermented foods regularly, likely due to the anecdotal results they witnessed.24 Indigenous people have patterns of illness very different from Western civilization; yet, they rapidly develop diseases, once exposed to Western foods and lifestyles.25, 26
Beneficial microbes in fermented foods can decrease anxiety, diminish perceptions of stress, and improve mental outlook.27 Brain derived neurotrophic factor (BDNF) can be increased via either probiotics, or fermented foods.28 BDNF is found in regions of the brain that control eating, drinking, and body weight; it likely contributes to the management of these functions.29 Stress is also known to alter gastrointestinal microflora.30 Probiotics and fermented foods can help to lower systemic inflammatory cytokines, decrease oxidative stress, improve nutritional status, and correct SIBO.31
In one study, researchers even linked gut microbes to autism.32 In their study, a probiotic was found to help. This brings us to the possible exciting conclusion that probiotics and large servings of fermented foods may provide therapeutic strategies for neurodevelopmental disorders.33
Interestingly, researchers have also found that propionic acid, which is a short-chain fatty acid produced by microbiota, can have negative effects on health and behavior. A number of inherited and acquired conditions, such as propionic/methylmalonic acidemia, biotinidase/holocarboxylase deficiency, ethanol/valproate exposure, and mitochondrial disorders, are all known to result from elevations of propionic acid and other short-chain fatty acids.34
The Western diet traditionally produces an unfavorable ratio of ‘good vs. bad’ gut flora.35 In addition, gut flora can help regulate fat storage.36 So not only are you more likely to have neurological problems, with a poor ratio of gut flora, but you are more likely to become obese.37 Hopefully all this information has driven home the fact that the Paleo Diet, which is anti-inflammatory, and rich in fermented foods, will deliver a positive ratio of healthy gut bacteria. It may seem like a small change, but it can make all the difference in the world, when it comes to your health.
 Steinkraus KH: Comparison of fermented foods of the East and West. In Fish Fermentation Technology. Edited by Lee CH, Steinkraus KH, Reilly PJ. Tokyo: United Nations University Press; 1993:1-12.
 Steinkraus, K.H. (2002), Fermentations in World Food Processing. Comprehensive Reviews in Food Science and Food Safety, 1: 23–32.
 Park KY, Jeong JK, Lee YE, Daily JW. Health benefits of kimchi (Korean fermented vegetables) as a probiotic food. J Med Food. 2014;17(1):6-20.
 Hidaka BH. Depression as a disease of modernity: explanations for increasing prevalence. J Affect Disord. 2012;140(3):205-14.
 Cho I, Blaser MJ. The human microbiome: at the interface of health and disease. Nat Rev Genet. 2012;13(4):260-70.
 Spalding A, Kernan J, Lockette W. The metabolic syndrome: a modern plague spread by modern technology. J Clin Hypertens (Greenwich). 2009;11(12):755-60.
 Edwardson CL, Gorely T, Davies MJ, et al. Association of sedentary behaviour with metabolic syndrome: a meta-analysis. PLoS ONE. 2012;7(4):e34916.
 Swain MR, Anandharaj M, Ray RC, Parveen rani R. Fermented fruits and vegetables of Asia: a potential source of probiotics. Biotechnol Res Int. 2014;2014:250424.
 Rechenberg K, Humphries D. Nutritional interventions in depression and perinatal depression. Yale J Biol Med. 2013;86(2):127-37.
 Bourre JM. Effects of nutrients (in food) on the structure and function of the nervous system: update on dietary requirements for brain. Part 1: micronutrients. J Nutr Health Aging. 2006;10(5):377-85.
 André C, Dinel AL, Ferreira G, Layé S, Castanon N. Diet-induced obesity progressively alters cognition, anxiety-like behavior and lipopolysaccharide-induced depressive-like behavior: focus on brain indoleamine 2,3-dioxygenase activation. Brain Behav Immun. 2014;41:10-21.
 Sánchez-villegas A, Toledo E, De irala J, Ruiz-canela M, Pla-vidal J, Martínez-gonzález MA. Fast-food and commercial baked goods consumption and the risk of depression. Public Health Nutr. 2012;15(3):424-32.
 Agrawal R, Gomez-pinilla F. ‘Metabolic syndrome’ in the brain: deficiency in omega-3 fatty acid exacerbates dysfunctions in insulin receptor signalling and cognition. J Physiol (Lond). 2012;590(Pt 10):2485-99.
 Kodl CT, Seaquist ER. Cognitive dysfunction and diabetes mellitus. Endocr Rev. 2008;29(4):494-511.
 Jacka FN, Mykletun A, Berk M, Bjelland I, Tell GS. The association between habitual diet quality and the common mental disorders in community-dwelling adults: the Hordaland Health study. Psychosom Med. 2011;73(6):483-90.
 Borresen EC, Henderson AJ, Kumar A, Weir TL, Ryan EP. Fermented foods: patented approaches and formulations for nutritional supplementation and health promotion. Recent Pat Food Nutr Agric. 2012;4(2):134-40.
 Conterno L, Fava F, Viola R, Tuohy KM. Obesity and the gut microbiota: does up-regulating colonic fermentation protect against obesity and metabolic disease?. Genes Nutr. 2011;6(3):241-60.
 Flint HJ. Obesity and the gut microbiota. J Clin Gastroenterol. 2011;45 Suppl:S128-32.
 Parekh PJ, Arusi E, Vinik AI, Johnson DA. The role and influence of gut microbiota in pathogenesis and management of obesity and metabolic syndrome. Front Endocrinol (Lausanne). 2014;5:47.
 Sandoval DA, Seeley RJ. Medicine. The microbes made me eat it. Science. 2010;328(5975):179-80.
 Hemarajata P, Versalovic J. Effects of probiotics on gut microbiota: mechanisms of intestinal immunomodulation and neuromodulation. Therap Adv Gastroenterol. 2013;6(1):39-51.
 Szaefer H, Licznerska B, Krajka-kuźniak V, Bartoszek A, Baer-dubowska W. Modulation of CYP1A1, CYP1A2 and CYP1B1 expression by cabbage juices and indoles in human breast cell lines. Nutr Cancer. 2012;64(6):879-88.
 Chelule PK, Mbongwa HP, Carries S, Gqaleni N. Lactic acid fermentation improves the quality of amahewu, a traditional South African maize-based porridge. Food Chem. 2010;122:656–661.
 Anukam KC, Reid G. African traditional fermented foods and probiotics. J Med Food. 2009;12(6):1177-84.
 Lipski E. Traditional non-Western diets. Nutr Clin Pract. 2010;25(6):585-93.
 Llaverias G, Danilo C, Wang Y, et al. A Western-type diet accelerates tumor progression in an autochthonous mouse model of prostate cancer. Am J Pathol. 2010;177(6):3180-91.
 Bested AC, Logan AC, Selhub EM. Intestinal microbiota, probiotics and mental health: from Metchnikoff to modern advances: part III – convergence toward clinical trials. Gut Pathog. 2013;5(1):4.
 Bercik P, Denou E, Collins J, et al. The intestinal microbiota affect central levels of brain-derived neurotropic factor and behavior in mice. Gastroenterology. 2011;141(2):599-609, 609.e1-3.
 Binder DK, Scharfman HE. Brain-derived neurotrophic factor. Growth Factors. 2004;22(3):123-31.
 Logan AC, Katzman M. Major depressive disorder: probiotics may be an adjuvant therapy. Med Hypotheses. 2005;64(3):533-8.
 Dinan TG, Stanton C, Cryan JF. Psychobiotics: a novel class of psychotropic. Biol Psychiatry. 2013;74(10):720-6.
 Gilbert JA, Krajmalnik-brown R, Porazinska DL, Weiss SJ, Knight R. Toward effective probiotics for autism and other neurodevelopmental disorders. Cell. 2013;155(7):1446-8.
 Parvez S, Malik KA, Ah kang S, Kim HY. Probiotics and their fermented food products are beneficial for health. J Appl Microbiol. 2006;100(6):1171-85.
 Macfabe DF. Short-chain fatty acid fermentation products of the gut microbiome: implications in autism spectrum disorders. Microb Ecol Health Dis. 2012;23
 Turnbaugh PJ, Ridaura VK, Faith JJ, Rey FE, Knight R, Gordon JI. The effect of diet on the human gut microbiome: a metagenomic analysis in humanized gnotobiotic mice. Sci Transl Med. 2009;1(6):6ra14.
 Bäckhed F, Ding H, Wang T, et al. The gut microbiota as an environmental factor that regulates fat storage. Proc Natl Acad Sci USA. 2004;101(44):15718-23.
 Ley RE, Bäckhed F, Turnbaugh P, Lozupone CA, Knight RD, Gordon JI. Obesity alters gut microbial ecology. Proc Natl Acad Sci USA. 2005;102(31):11070-5.