Symbiotic microbes participate in both our body and our metal health. Our intestinal microbes affect our brain using a communication system (the so called gut-brain axis) that goes beyond our proper structures (nerves, blood, hormones, neurotransmitters). This is a field of research that has been sprouting only recently giving new insights on how our behaviour and mood can be controlled by something other that "us". This research suggests to take good care of our internal guests.
What we are is what we eat….also because of how we feed our microbes! Thus, the diet we maintain can have specific consequence on our moods and behaviour since what we eat makes up what type of bacteria inhabit our intestine, and these bugs appear to have a lot to do with our brain functioning.
If food affects bacteria and bacteria affect the brain, than we could talk about “Food for a good mood” (hints here below...). Some well-known effects of the typical Western diet (highly processed food, heavily loaded by sweetened desserts, fried food, processed meat, refined grains, high-fat dairy, fast-food), too rich in bad fats and low-fiber carbohydrates, are:
- weakened gut barrier, which loses its selectivity, and
- disturbed cognitive performance.
Moreover, what identifies the typical Western diet is also the presence of high fructose corn syrup, added to many food items (packaged food) and juices. High fructose, besides being bad for the liver, increases the harmful bacterial lipo-polysaccharides and adds another component in the explanation on how sugar is linked to depression.
Diets dominated by proteins, as often the Western diets are, were already shown in 1910 to be able to shift the bacterial microflora, increasing certain types of bacteria and decreasing lactobacillus and bifidobacterium spp. This change would also lead to some behavioural changes (lassitude, cognitive difficulties and disinterest in stimuli).
On the opposite, a Mediterranean diet (rich in whole food, fruits and fibers, vegetable proteins, fish, olive oil) is associated with lowered risk of depression and anxiety.
Not only it is important to preserve a god amount of good gut bacteria, it is also very important to maintain a high variety of bacteria in the gut. Bacteria diversity is important to our health as species diversity is necessary for the health of an ecosystem: a loss of bacterial biodiversity is associated with digestive tract disorders, skin conditions and also obesity.
Certain diets would create a high diversity of the intestinal microbiota, and, as a consequence: - decreased signs of anxiety, and improved cognition. For example, diets that contain high-fiber and fermented foods, vegetables and fish (like traditional or not-fast food-containing diets, that often include bacteria, such as in fermented soy food in Japan, kimchee in Korea, kefir in Russia etc.) lead to higher amounts of Bifidobacterium and Lactobacillum and higher biodiversity.
It is interesting to note that diminished environmental biodiversity (lower number of plant species) in the proximity of homes is associated with lower bacterial biodiversity on the skin of people who present allergy. And similarly, richness in biodiversity of vegetation and birds within urban environments is positively associated with mental well-being, through an increased richness of gut microbiota!
Bacteria, even the ones that inhabit our gut, are found in nature, in the soil, water and plant food. If we impoverish our environment and loose species of plants and animals - and thus bacteria-, or if we live in an environment remote from nature and deprived of species, we are more prone to diseases, both physical and mental.
What are then the specific food items that potentiate our cognitive functions and our moods thanks to the bacteria response to them?
have all being proven to show beneficial effects on gut microbiota, they:
- increase Lactobacillus and Bifidobacterium,
- protect gut permeability and
- protect blood brain barrier permeability
- lower risk of depression,
- lower cognitive decline and
- improve resistance to stress.
In addition, all these food items have high anti-oxidant potential and help prevent the inflammatory process in the blood as well as in the brain.
Some specific minerals are also necessary to keep a well fucntioning gut biota. A diet low in magnesium and zinc (found in vegetables and nuts) is associated with intestinal permeability and loss of bifidobacteria and lactobacilli. Such diet is also linked to depression.
Waht about fats? Although trans-fatty acids or (bad) fat fast food and commercial bakery products are associated with higher depression, also a diet poor in other (good!) oils, omega-3 fatty acids and olive oil, has the same effects. A diet deficient in omega 3 (oily fish, flax, walnuts) also increases the risk of an overgrowth of pathogenic bacteria in the small intestine which, as we saw earlier, increases the risk of anxiety and depression. Thus not all fats are the same and omega 3 and olive oil are strong anti-oxidants, protect the gut barrier and are related to a reduced depression risk.
Imbalance of the gut microbiota is created by infection, use of antbiotics, over-vaccination, overgrowth of abnormal microbiota due to poor intestinal mobility caused by low fiber-high processed food etc. Such microbes imbalance has been found in:
autism, asthma, allergy, chron’s disease, atherosclerosis, fat liver disease, cirrhosis, inflammatory bowel disease, rheumatoid arthritis, multiple sclerosis, eczema, dermatitis, cystic fibrosis, pancreatitis, food allergy.
Use of probiotics: probiotics are a “live microbial …supplement which beneficially affects the host…. by improving its intestinal microbial balance”. (Fuller, 1989)
Priobiotics are often prescribed and effective for compensating the use of antibiotics and restore the normal intestinal microbial composition. However, when such probiotics are no longer consumed, the added bacteria are rapidly eliminated by the colon. But although probiotic might not have a great permanent impact on the gut flora, a single strain of lactobacillus or bifidobacterium can improve overall microbial diversity. Further, probiotics help in:
- removal of environmental toxins from the gastrointestinal tract,
- prevention of intestinal permeability,
- reduction in systemic oxidative stress,
- promotion of immunity,
- compensation of fatigue and depression,
- neurotransmitter production,
- treatment of diarrhoea,
- symptomatic relief of irritable bowel syndrome,
- improvement of fasting insulin levels and glucose metabolism
- Limitation of gastric/intestinal pathogens (e.g. Helicobacter pylori)
Example of strains used in therapy:
- Lactobacillus plantarum C29, isolated from Asian kimchi, can increase the production of a hormone in the hippocampus which preserves nerve cells and encourages their growth.
- L. rhamnosus IMC 501 and L. paracasei IMC 502 minimize the systemic oxidative stress associated with intense physical activity.
- Lactobacillus casei has been successfully used in experiments to fight depression and chronic fatigue.
In order to facilitate the implantation of new bacteria in the gut, use of prebiotics accompany the probiotic supplementation. Prebiotic are growth substrates feeding beneficial bacteria. Among these, fructooligosaccharides are the only efficiently used ones. They include oligofructose and inulin, found in capsules or in natural food: garlic, onion, asparagus, artichocke contain such prebiotics naturally.
Most strains of Bifidobacterium use this type of food and ferment it to produce short chain fatty acid (SCFA) that are food to colonic cells, liver, muscles and other tissues. As an example, in irritable bowel syndrome, the oral consumption of a prebiotic significantly reduced anxiety while increasing bifidobacteria.
Therapeutic use of probiotics and prebiotics are usually supplemented by other gut nutrients that repair the intestinal barrier: L-glutamine, butyric acid, short chain fatty acids, which are normally created by bacteria from carbohydrates reaching colon (fibers), EPA-GLA essential oils, gamma-orynazol (found in rice bran oil).
TO SUMMARIZE: FOOD FOR YOUR MOOD to lower depression, anxiety and improve cognitive function
Probiotics: good bacteria to add to the gut, found in food: fermented soy, fermented cabbage, kefir, live fermented yogurt
Prebiotics: fibers feeding good bacteria found in onions, garlic, artichockes, asparagus
Food for mood: cocoa, honey, blueberries, bananas, pomegranate, green tea, coffee; omega 3, olive oil.
Mediterranean diet: high fibers, vegetables, fruit, fish, complex carbohydrates
Addolorato G, et al.2008 State and trait anxiety and depression in patients affected by gastrointestinal diseases: Psychometric evaluation of 1641 patients referred to an internal medicine outpatient setting. Int J Clin Pract 62:1063–1069.
Akbaraly TN, Brunner EJ, Ferrie JE, Marmot MG, Kivimaki M, Singh-Manoux A. 2009, Dietary pattern and depressive symptoms in middle age. Br J Psychiatry. 2009 Nov;195(5):408-13. doi: 10.1192/bjp.bp.108.058925.
Arnold L 1929 Alterations in the endogenous enteric bacterial flora and microbic permeability of the intestinal wall in relation to the nutritional and meteorological changes. J Hygiene 1929, 29:82–116
Bested et al. 2013 III Intestinal microbiota, probiotics and mental health: from Metchnikoff to modern advances: part III – convergence toward clinical trials, Gut Pathogens 2013, 5:4
Fuller, R. 1989 Probiotics in man and animals. J. Appi. Bacteriol.
Gibson, G.R., Roberfroid, M.B.1995 Dietary Modulation of the Human Colonie Microbiota: Introducing the Concept of Prebiotics American Institute of Nutrition.
Herter CA, Kendall AI 1910 The influence of dietary alterations on the types of intestinal flora. J Biol Chem
1910, 7:203 –36
Ley RE, et al.2008 Evolution of mammals and their gut microbes. Science 320:1647–1651.
Lavasani S, Dzhambazov B, Nouri M, Fak F, Buske S, Molin G, et al. 2010 A novel probiotic mixture exerts a therapeutic effect on experimental autoimmune encephalomyelitis mediated by IL-10 producing regulatory T cells. PLoS One. 2010; 5: e9009.
Lindeberg S. 2012 Paleolithic diets as a model for prevention and treatment of Western disease. Am J Hum Biol 2012, 24:110–115.
Logan, A.C. Martin Katzman 2005. Major depressive disorder: probiotics may be an adjuvant therapy, Medical hypotheses, 64, 3: 533-538 (http://www.medical-hypotheses.com/article/S0306-9877%2804%2900496-7/abstract)
Miura H, Ozaki N, Sawada M, Isobe K, Ohta T, Nagatsu T. 2008 A link between stress and depression: shifts in the balance between the kynurenine and serotonin pathways of tryptophan metabolism and the etiology and pathophysiology of depression. Stress 2008, 11:198-209.
Maes, M., Marta Kubera and Jean-Claude Leunis 2008 The gut-brain barrier in major depression: Intestinal mucosal dysfunction with an increased translocation of LPS from gram negative enterobacteria (leaky gut) plays a role in the inflammatory pathophysiology of depression, Neuroendocronology letters, 29, 1, 117-124
Mohammadi, D. 2015 Could an inflamed brain be a hidden cause of depression?, New Scientist, 29 June 2015
Nikolov RN, et al. 2009 Gastrointestinal symptoms in a sample of children with pervasive developmental disorders. J Autism Dev Disord 39:405–413
Ochoa-Repáraz J, Mielcarz DW, Wang Y, Begum-Haque S, Dasgupta S, Kasper DL, et al. 2010 A polysaccharide from the human commensal Bacteroides fragilis protects against CNS demyelinating disease. Mucosal Immunol. 2010; 3: 487-495.127.
Riaza Bermudo-Soriano C, Perez-Rodriguez MM, Vaquero-Lorenzo C, Baca-Garcia E 2012 New perspectives in glutamate and anxiety. Pharmacol Biochem Behav 2012, 100:752–774.
Sanchez-Villegas, A. and Miguel A Martínez-González 2013 Diet, a new target to prevent depression?. BMC medicine, 11, 3
Seckl JR, Meaney MJ 2004 Glucocorticoid programming. Ann N Y Acad Sci 1032:63–84.
Skarupski,K.A., C.C. Tangney, H. Li, D.A. Evans, and M.C. Morris, 2013 Mediterranean Diet and Depressive Symptoms Among Older Adults Over Time, J Nutr Health Aging. 2013; 17(5): 441–445.
Tsai YC, Chiu Li W, Dowd SE, Scurlock B, Acosta-Martinez V, Lyte M. 2009 Memory and learning behavior in mice is temporally associated with diet-induced alterations in gut bacteria. Physiol Behav 2009, 96:557–567.
Wang, Y. et al. 2014, An intestinal commensal symbiosis factor controls neuroinflammation via TLR2-mediated CD39 Signalling, Nature Communication, July 1014, 5, 4432
Wang, Y. et al. 2014, A commensal bacterial product elicits and modulates migratory capacity of CD39+ CD4 T regulatory subsets in the suppression of neuroinflammation, Gut Microbes 5:4, 1–10