You know the usual suspects behind your terrible mood: lousy customer service, unresolved arguments, and maybe even a tight deadline at work. One thing's clear. You have very little control over these external factors. But hey, what if there was something you could change in your life that'll give your mental state a little lift? Here’s a clue: it has something to do with the single-celled organisms that reside in your gut. In other words, your gut microbiome.
Research has increasingly demonstrated a link between mood disorders and damage to the gut microbiota, to be more specific (1). Scientists term the communication between the gut and brain as the 'gut-brain axis'–and this article covers everything we know about the concept so far.
The Link Between Gut Bacteria And Mood
Below, find an exploration of research that shows a clear association between gut bacteria and mood.
Gut Bacteria And Psychiatric Disorders
According to a 2017 review published in the Journal of Psychiatry & Neuroscience, several studies highlight the finding that patients with gastrointestinal disorders (i.e. inflammatory bowel disease and irritable bowel syndrome) have higher rates of anxiety and depression than the general population (2, 3). The opposite holds, too. Individuals with anxiety and depression present more GI symptoms than healthy controls (4).
Researchers have also noticed that certain species of bacteria–mainly belonging to the genus Bacteroides–are more likely to be found in the guts of depressed patients, while those linked to better mood (primarily the genera Blautia and Eubacterium) are lacking (5). Another convincing finding that fortifies the link between gut bacteria and depression: when formerly carefree rodents in a 2017 study published in European Neuropsychopharmacology were inoculated with bacteria from depressed individuals, they developed signs of the condition (6).
Gut Microbiome And The Population At Large
As of now, it might seem as though your gut microbiome only affects your risk of having a psychiatric disorder. But the truth is that the connection between gut microbiome and mood affects us all. Even in the absence of a clinical case of depression or anxiety. A growing body of research suggests that a well-balanced microbiome can be vital to easing everyday stresses and keeping the blues at bay even in otherwise healthy individuals. A 2015 study published in Brain, Behavior, and Immunity, for instance, found that a positive shift in gut bacteria populations resulted in significantly fewer reports of sad mood and negative thoughts (7).
How Does Gut Bacteria Alter Mood?
If you’ve read thus far, this question must be on your mind: “How can these unintelligent, simple organisms in my gut affect higher functions in my brain?” It’s a curious phenomenon indeed. A quick disclaimer before diving in. It must be said that scientists have only begun to probe the mechanisms by which the microbiome might be altering mood–and driving the mental health disorders it appears to be associated with. There's a lot more to learn, and nothing's for sure yet. Regardless, researchers currently believe that there are multiple physical and biochemical pathways through which your gut and brain are connected.
#1 – The Vagus Nerve
The vagus nerve is the longest cranial nerve in your body, connecting most of the major organs between your brain and colon–like a system of roots or cables (8, 9). That means it connects your gut and brain. It's known to send signals in both directions. Therefore, it was an obvious suspect when scientists wanted to study the mechanism behind brain-gut interactions. And, of course, it appears that there is at least some evidence for this.
Various animal studies, for example, find that when stress inhibits the signals sent through the vagus nerve, gastrointestinal problems arise (10). Interestingly enough, there have been animal studies documenting that when the vagus nerve is severed, gut bacteria's effects on brain biochemistry, stress response, and behavior evaporate (11)! Similarly, a 2014 human study published in PLOS ONE found that individuals with irritable bowel syndrome or Crohn's disease had reduced vagal tone, suggesting a reduced vagus nerve function (12). These are all clear signs that the vagus nerve is likely to play an important, mediating role in the gut-brain axis.
#2 – Neurotransmitters
Scientists have also found that the gut bacteria produce neurotransmitters such as serotonin, dopamine, and GABA–all of which are chemical messengers that play a crucial role in mood regulation (13, 14). As outlined by a 2014 review published in the Journal of Medicinal Food, Lactobacillus species produce acetylcholine and GABA; Bifidobacterium species produce GABA; Escherichia species produce norepinephrine, serotonin, and dopamine, while Bacillus species produce norepinephrine and dopamine (15). But what do these neurotransmitters do, exactly?
Well, let’s first take a look at serotonin. It's thought to regulate anxiety, happiness, and mood (16, 17, 18, 19). Low serotonin levels have been associated with depression, and increased levels of it brought on by medication (e.g. SSRIs) are thought to decrease arousal. As for dopamine, it’s known as the ‘feel-good’ neurotransmitter–and understandably why. It contributes to feelings of alertness, focus, motivation, and happiness. Disaster strikes when you have too much of it, though. In excess, dopamine can contribute to psychiatric disorders like mania, hallucinations, and delusions (20, 21, 22). So, ultimately, gut bacteria's ability to produce these mood-altering neurotransmitters, thereby offers scientists a greater understanding of the connection between gut and mental health.
#3 – Short-Chain Fatty Acids
In addition to producing neurotransmitters, your gut bacteria are also responsible for producing short-chain fatty acids (SCFA) such as butyrate, propionate, and acetate through the fermentation of dietary fiber (23). Other than exerting local effects in the gut and peripheral tissues, scientists are now beginning to speculate that SCFAs play a pivotal role in microbiota-gut-brain crosstalk. This is supported by animal studies suggesting a decrease in SCFAs level is implicated in the onset of depression (24). In line with this, clinical evidence has shown that SCFA concentrations are lower in individuals with depression than in controls (25, 26).
Moreover, current scientific literature shows that butyrate possesses an antidepressant-like effect that reverses behavioral alterations in mouse models, such as low energy, anhedonia, and cognitive and sociability impairments (27, 28, 29). Therefore, taking into account all these studies, it’s evident that SCFAs are a possible means of communication between the gut microbiome and the brain.
#4 – Inflammation
Researchers also believe that stress-induced changes to the microbiome may, in turn, affect the brain and mood. For instance, a few studies suggest that defensive molecules your gut produces during infection (known as inflammatory cytokines) disrupt brain neurochemistry–and can make you more vulnerable to anxiety and depression (30, 31, 32). In line with this, experimental evidence links changes in the chemokine network to depressive behavior. And researchers of clinical studies have also indicated an association between neuroinflammation and depression (33).
What Can You Do To Improve Gut Health?
Chances are, you’re already wondering how you can improve your gut health. Well, there are indeed a few things you can do. Arguably most important of all: ensure you eat a diverse range of foods which will, in turn, lead to a diverse microbiota; this is because the more species of bacteria you have living in your gut, the greater the number of health benefits they may be able to contribute (34, 35, 36, 37, 38).
One cannot overstate the importance of regular physical exercise. In addition to its benefits for cardiovascular health, research also suggests that it may improve gut health (39). For instance, a 2014 study published in Gut found that athletes had a large variety of gut flora compared to nonathletes–hinting at the possibility that working out may increase gut microbiome diversity (40). Getting enough sleep (at least 7 hours of quality sleep nightly) is also crucial if you wish to improve your gut health. A 2014 animal study published in PLOS ONE indicated that irregular sleep habits and disturbed sleep could have adverse outcomes for the gut flora, which may increase the risk of inflammatory conditions (41).
And of course, when it comes to improving your gut health, one strategy that’s been consistently backed by science is this: probiotics. A small 2016 study published in Nutrition found that when participants with major depression took a probiotic supplement for 8 weeks, most of them had lower scores on the Beck Depression Inventory, a common method of evaluating depression symptoms (42). A 2017 review also found that daily probiotic supplementation seemed to alleviate depression and anxiety symptoms (43).
A Note On Supplementing With Probiotics
Searching for a suitable probiotics supplement? Look no further than Dr. Danielle’s Probiotics; it contains Bacillus spores specifically chosen for their natural, hardy outer shell that guards the spore against destructive factors like heat and stomach acid.
Oh, by the way: supplementing with probiotics isn’t going to cut it if your gut lining is unhealthy. That’s because it may become too porous–allowing toxins, bacteria, and partially digested food to reach the tissues below it (44, 45). This can, in turn, harm the ‘good’ bacteria in your gut (what a waste of probiotics!) To prevent that, supporting the health of your gut lining is crucial. And for that, there is nothing better than Dr. Danielle’s Gut Assist; its unique formula helps boost your gut lining’s ability to defend itself against the daily assaults from all kinds of stressors (e.g. toxins and pathogens).
Takeaway? You’ll have to boost your gut’s population of ‘good’ bacteria (through probiotics)–while making sure your gut lining is in the best shape possible (through Gut Assist). This two-pronged strategy will get you the best possible gut health in record-breaking time.