Did you ever notice how quickly a thought triggers a feeling in the gut? When something frightens you, a bad thought, and you feel like an elevator is plummeting in your tummy. Or, when you anticipate something fun, it rises.
But perhaps you have noticed that during periods of high stress, things you normally eat can suddenly cause gastric issues, such as bloating, constipation, cramping, stomach griping, and diarrhea. In some people who are exceptionally sensitive, a mere stressful thought can trigger some gut spasms. Some people under stress totally lose their appetite, while others can’t turn it off and gorge.
It’s all due to the gut-brain axis -- a more recently understood and explored aspect of physiology.
What is the Gut-Brain Axis?
In the 1960s and 1970s, researchers discovered several peptides that dually resided in the brain and gastrointestinal tract, leading to the concept of the brain controlling GI function and coining the term “gut-brain axis (GBA).”
The GBA is complex but it involves direct, lightning-fast communication both ways (bilateral) between the GI tract (gut) and the brain. The GBA ensures proper functioning and maintenance of gastrointestinal homeostasis (“healthy balance’), and it has been increasingly shown to have numerous effects on motivation, affect, and some cognitive abilities. It also serves to connect the cognitive and emotional brain centers with GI functions, including immune response and intestinal permeability, among other mechanisms. Biochemical activity involved in GBA communication involve neuro-immuno-endocrine mediators.
The GBA network entails the central nervous system (CNS), brain and spinal cord, autonomic nervous system (ANS), enteric nervous system (ENS) and the hypothalamic pituitary adrenal (HPA) axis. The ANS is the part of the nervous system that controls activity not consciously controlled, such as breathing, heartbeat, and digestion, while the ENS is a significant part of the ANS specifically governing the GI tract. The HPA is the central stress response system, which is influenced by the hypothalamus’ secretion of corticotropin-releasing factor (CRF), which encourages the pituitary gland to release adrenocorticotropic hormone (ACTH) which in turn stimulates release of cortisol – the stress hormone that also causes accelerated production of pro-inflammatory cytokines. This pathway of communication allows the brain to influence several specific cells that themselves tend to be influenced by the gut microbiota.
Due to continued clarification of what is involved in and influences the gut-brain axis, say some researchers, “the concept of a microbiome GBA is now emerging.”
One area of gastrointestinal health involving the microbiome and the GMA is irritable bowel syndrome (IBS), which is a dysfunction in the GI tract causing altered bowel movements from constipation to mucus-laden diarrhea accompanied by painful cramps.
Other characteristics of IBS include visceral hypersensitivity, food sensitivity, poor carbohydrate absorption and intestinal inflammation. And if this pile of discomforts wasn’t enough, people with IBS also tend to have anxiety and depression more than people who don’t have IBS.
By 2014, according to one research team, the idea that the pathogenesis of IBS is largely influenced by a dysregulated gut-brain axis has largely become medically accepted, and that the gut microbiome has shown to be pivotal in both onset and worsening of symptoms. Additionally, they point out, microbiota manipulation has been reliably shown to impact IBS symptoms.
Another research team agrees that “Alterations in the bidirectional interactions between the intestine and the nervous system have important roles in the pathogenesis of irritable bowel syndrome (IBS). A body of largely preclinical evidence suggests that the gut microbiota can modulate these interactions.”
One placebo-controlled study of 77 men and women looked at how probiotic strains -- L. salivarius UCC4331, Bifidobacterium infantis 35624 -- affected inflammatory state in bowel function in those with IBS. At the beginning of the study they exhibited an abnormal ratio of interleukin-10 to interleukin-12, signifying a pro-inflammatory state. The team found that the B. infantis 35624 group had a more normalized ratio at the study’s end.
What is the Role of the Microbiota in the Gut-Brain Axis?
Bacterial residents in the gut microbiota have been shown to influence the GBA through several ways.
Gut hormone (neuroendocrine) signaling: Microbial byproducts stimulate the production of neuropeptides that circulate int eh bloodstream and influence the ENS.
Vagus nerve: This brain stem nerve connects to the abdomen and other areas in the body. It contains neurons that communicate with the hypothalamus and limbic system (emotional seat).
Stimulates tryptophan metabolism: The majority of serotonin is produced in the gut. The “feel good” hormone also helps regulate gastrointestinal secretion, bowel motility. The microbiota stimulates tryptophan metabolism, which creates serotonin. In addition, some strains of Lactobacillus and Bifidobacteria produce other “feel good” biochemicals such as gamma amino-butryic acid – the primary inhibitory neurotransmitter (helps promote calm and block anxiety). Another “happy” neurochemical, dopamine, is also produced by some bacillus strains. As mentioned, probiotics also make butyric acid and other short-chain fatty acids that stimulate release of serotonin and the sympathetic nervous system.
Stress-induced intestinal permeability: Leaky gut syndrome (intestinal permeability) is induced by chronic stress that increases inflammation, which increases risk of development of psychiatric disorders. Some research has concluded that the gut microbiota produce neuroactive chemicals that can support psychiatric well-being.
How do Probiotics Support the Gut-Brain Axis?
Within the past dozen years, increasing number of studies have identified a bidirectional relationship between the gut microbiome and brain function (microbiota-gut-brain axis). Supporting the gut-brain axis is accomplished primarily through replenishing and sustaining a robustly diverse microbiota by consuming the proper variety and abundance of probiotic strains that work chiefly to regulate mood, anxiety and neurotransmitters.
There are compelling studies validating the role of the microbiota in regulating depressive behaviors and anxiety. One study illuminated the how alterations in the microbiota induces stress-related behaviors. Another review states that a balanced microbial community is key in regulating health, and “it seems likely that gut microbiota plays a role in depression.”
Further scientific analysis of how probiotics influence the microbiome may provide potential preventative measures for depressive and anxiety disorders.
One scientific review sought to substantiate potential preventative roles of probiotics in the gut microbiota to major depressive disorder and anxiety disorders. Data suggested that the gut microbiota communicates with the central nervous system through endocrine, neural and immune mechanisms, and that the microbiota assists in regulating stress response through the hypothalamic-pituitary-adrenal axis. They found that overall, probiotics reduce anxiety and depressive-like behaviors.
One study showed that L. rhamnosus (JB-1) may have a direct effect on neurotransmitter receptors in the CNS. The probiotic was shown to reduce stress-induced anxiety- and depression-related behavior. Further, the researchers confirmed that the vagus nerve is a major communication pathway between the brain and the bacteria in the gut. They concluded, “Together, these findings highlight the important role of bacteria in the bidirectional communication of the gut–brain axis.”
What Can I Do to Support My Gut-Brain Axis?
The GBA, as we have seen, influences how we feel – and even think (cognitive behavior). It is affected by stress and diet.
Take probiotics: Probiotics are essential to a sturdy health profile as they seed your microbiota, helping it to flourish and keep you resilient in times of significant stress. The good news is that there are many strains, and you don’t have to take a wide variety of pills; probiotics are now available in convenient and tasty dosage forms such as Microshots, as well as appearing in foods beyond yogurt.
Reduce consumption of animal fats: Fats from meat, especially processed meats (deli sandwiches, for example) contain pro-inflammatory agonist arachidonic acid (an omega-6 fatty acid). Further, bad fats can induce alterations in the gut’s microbial signaling to the brain. Fish, however, is a preferred animal food as it contains both essential omega 3 fatty acids DHA and EPA, which have tremendous benefits to the brain.
Exercise regularly and breathe deeply: Exercise releases endorphins that accentuate that “feel good” sensation. Breathing deeply – when you inhale as much as possible, hold it and let it out slowly – induces mental relaxation and clarity as well as physical relaxation. Both activities help support your GBA.
Learn to listen to yourself: When you have thoughts or emotions, your body reacts. When you feel stressed, anxious or depress, there is typically chatter going on in your brain. Take moments to listen to this chatter. Be mindful of the gut feelings certain statements and thoughts are churning in your gut. Work with professionals – or simply talk it out with loved ones so that you can develop strategies to cope and counteract those thought stressors.
Your gut feelings are indeed real. And the connection – the gut brain axis – is a critical link to wellness when being supported via healthy lifestyle and regular probiotic consumption.