The Link Between Stress and IBS, Part 2
For anyone who suffers with Irritable Bowel Syndrome (IBS), the road to improved gut health may feel impossible or, at the very least, a long and arduous journey. IBS is a very complicated disorder that involves many other aspects of your health and life, but there is hope and that is what this three-part article series is all about! Part One of this article series, featured in the last issue of ELMTM Maine, talked about the six contributing factors of Irritable Bowel Syndrome (IBS), how the body responds to stress and the role stress plays in IBS. Today, we dive a little deeper into how the state of the community of bugs living in your digestive tract (aka your gut microbiota) can effect and be effected by stress as well as influence whether you will suffer from IBS.
The Direct Effects of Stress on Gut Microbiota
The terms gut microbiota and gut microbiome are usually used interchangeably, however there is an actual distinction between them. The human gut microbiota is the collection of microbial cells living in the human digestive tract; the human gut microbiome is the actual genes of those microbial cells. So, the microbiota is your community of gut bugs and the microbiome is their cumulative genetic code. Amazingly, this community of symbiotic microbes consist of close to 400 different species, a majority of which belong to one of two phyla – Firmicutes and Bacteroidetes. The microbiome of these microbes is reported to have a colossal 3.3 million non-redundant genes, while the human genome consists of a mere 22,000 genes. This means the human body contains over 100 times more microbiota genes than human genes! Not all of these species, or their genes, reside in every human body, however. There has been similar microbiota found among family members, but there does not seem to be a core set of microbiota species shared among all humans. In fact, studies indicate the gut microbiota and microbiome differ substantially, up to an 80-90% difference, between individuals.
Whatever the microbiota variety is in each individual, this community of commensal bacteria is crucial to gut health. They produce enzymes which allow the body to absorb certain nutrients. They help balance the gut microbiota by creating an inhospitable environment for pathogenic species. Additionally, they can help maintain the integrity of the intestinal wall, produce neurotransmitters, regulate bowel movements, modulate visceral hypersensitivity and may even control anxiety – key characteristics that contribute to the remission or onset of IBS. More recently, research has also proposed a more complicated communication pathway between the gut and brain that includes the gut microbiota.
The Brain-Gut-Microbiota Axis
Just as the gut and brain send signals to each other, it has been found that the microbiota can also create a bidirectional communication with the brain. Similar to the HPA axis’s intricate network of checks and balances for the stress response (discussed in Part One), the microbiota becomes part of a complex system called the Brain-Gut-Microbiota (BGM) axis. The BGM axis connects the microbiota, enteric nervous system, sympathetic “fight or flight” nervous system, parasympathetic “rest and digest” nervous system, as well as hormonal and immune responses. Although the specific role of the microbiota within this brain-gut communication is still not fully defined, it is proposed that the microbiota influence the enteric nervous system and immune system, both of which effect the body’s stress response. Even if the microbiota’s role is not determined yet, the concept of the BGM axis is supported by studies that associate the stress response with microbiota balance.
Stress and the Microbiota
Research of numerous animal studies has indicated a strong correlation between stress and the microbiota. Studies have indicated that rats without commensal microbiota showed elevated levels of anxious behavior as well as impaired control of the stress response. Other studies have shown a link between depression and an altered microbiota and confirmed that different types of psychological stress altered the composition of animal microbiota. Additionally, HPA axis activity, the marker of the stress response, is consistently increased in studies of microbiota-deficient animals. In short, research shows stress negatively effects the microbiota. On a positive note, studies that showed an exaggerated HPA axis activity also indicated the stress response normalized after commensal bacteria were introduced. This further endorses the concept of a bidirectional communication between the brain and microbiota – stress can influence the state of the commensal bacteria and the commensal bacteria can influence the stress response.
This is very important information for IBS sufferers, especially understanding the role stress plays in IBS because the bidirectional interaction of the BGM axis has been implicated in IBS patients. According to the authors of The Intestinal Microbiota and Irritable Bowel Syndrome:
“Several animal and a few human studies indicate that the intestinal microbiota can be related to the altered pain-modulation processes as well as with the psychological, emotional, and behavioral disturbances often observed in IBS.”
This means the bidirectional communication between the brain and microbiota can influence and be influenced by stress. It’s becoming clear that stress not only contributes to the six leading factors in IBS (see Part One) but also plays a role in balancing the microbiota. Could this mean there is also a connecting link between microbiota balance and IBS symptoms?
Finding a Fundamental Connection Between IBS and Dysbiosis
Every town community in the United States, and the world, is usually rich with a diversity of characters, some good and some bad. If the town is suddenly overrun by the bad seeds, it corrupts the community. The same holds true for the microbial community living in each and every human gut. This community is full of a variety of beings with some good, and bad, characters. To keep the community healthy and happy the good guys need to keep the bad guys in check. However, if the shady characters create upheaval, it is the host – aka the human – that suffers.
There are three types of microbial characters. First, we have probiotics which are bacteria that create some kind of benefit to human health – such as regulating bowel movements or enhancing absorption of nutrients. Next is commensal bacteria which live in a symbiotic relationship with humans but may not create a direct benefit. Finally, pathogenic species such as some bacteria and viruses actually harm human health. When probiotic and commensal bacteria can keep pathogens at bay while also keeping their own population under control, the microbiota is considered healthy and in balance. However, if the pathogens start taking over, or there is overgrowth of commensal bacteria, the gut microbiota is considered to be in dysbiosis. It is this gut dysbiosis that may be the link connecting stress to the onset of IBS.
As mentioned previously, many studies have indicated stress can alter the gut microbiota and an altered gut microbiota, i.e. gut dysbiosis, can create stress on the body. Although there is not yet a clearly defined causative role linking gut dysbiosis to IBS, there is a trend of reduced beneficial bacteria and increased pathogenic species seen in IBS patients. Additionally, epidemiological observations have revealed a disruption of the microbiota – e.g. dysbiosis – often precedes development of IBS symptoms. Other clinical studies have confirmed differences in microbiota, specifically their stability and diversity, in IBS patients and IBS symptoms such as abdominal pain and bowel habits have been shown to be influenced by microbiota dysbiosis. When considering the role of stress, it has been suggested that changes in the microbiota due to stress may pave the way for any subsequent IBS symptoms. This stress-induced gut dysbiosis can even be linked to each of the six contributing factors of IBS.
Linking Gut Dysbiosis to the Six Contributing Factors of IBS
1. Altered brain-gut function
There is direct evidence that bacteria in the human gut communicates with the brain via the enteric nervous system (ENS). Additionally, the gastrointestinal tract can change the density of the microbiota through gut motility (movement through the digestive tract), intestinal permeability (leaky gut), immune response and release of gut hormones. The gut-brain communication can therefore effect and be affected by the microbiota. Additionally, certain probiotic bacteria such as Bifidobacterium infantis can control production of 5-HT, a key signaling substance in the brain-gut axis, promoting the microbiota’s influence on brain-gut function and IBS factors.
2. Abnormal gut motility
The production of 5-HT is also important for gut motility. One study found certain microbiota species typically found in a healthy gut promoted the production of serotonin (5-HT) in the large intestine which, in turn, controlled gut motility. Additionally, by-products produced by the gut microbiota, such as short chain fatty acids, can regulate movement through the digestive tract. A healthy gut microbiota can better regulate bowel movements, something IBS sufferers struggle with. Another possible sign of dysbiosis is increased volumes of methane gas in the intestinal tract which is produced by a species called Methanogens. Methane has been shown to reduce gut transit time, and, not surprisingly, this gas has been found in high volumes in IBS patients who suffer constipation.
3. Intestinal permeability
Part of the gut microbiota’s effects on gut motility and 5-HT production is due to its activation of the immune system caused by intestinal permeability (see Part One). Furthermore, gut microbiota may also lead to intestinal permeability. Two species that may be present in the microbiota, Ruminococcus gravus (R. gravus) and Ruminococcus torques (R. torques), have been shown to degrade the protective mucus layer of the intestines. These species have been seen in IBS-D and post-infection IBS patients. Another mucus degrading group of species, Akkermansia, may also be implicated in IBS patients. These microbiota species, through their damaging properties, may then initiate low grade inflammation.
4. Low-grade inflammation
In fact, it has been shown that the microbiota can trigger a proinflammatory state when there is increased intestinal permeability. Studies have indicated the microbiota engages the immune system of the gut and an altered gut microbiota may lead to an altered immune reaction. This, in turn, may generate a low-grade inflammatory response, creating a snowball effect of more intestinal permeability and low-grade inflammation. This is not the only road to inflammation though. A previous gut infection also creates an inflammatory response, activates the immune system and may invite more pathogenic species in, leading to dysbiosis. This pathogenic-dominant dysbiosis as well as an increase in inflammatory markers have been implicated in IBS patients.
5. Visceral hypersensitivity
The microbiota has also been shown to regulate visceral perception. Through the enteric nervous system, the microbiota can influence regions in the brain that interpret mood and stress-related information, process visceral pain perception and even initiate the body’s responses to this information. This may impact the severity of abdominal pain in IBS patients. Interestingly, visceral hypersensitivity can be induced by microbiota dysbiosis and this symptom can even be transferred from IBS patients to previously germ-free rats via the microbiota. Additionally, IBS patients who experienced pain in one study had over five times less Bifidobacteria compared to those without pain, highlighting the role of microbiota in IBS symptoms.
6. Psychosocial factors
The microbiota’s influence on bowel habits or visceral pain may in turn alter thoughts or emotions, especially considering visceral factors may impact upon human psychology. This seems logical when there are many viruses and bacteria that affect behavior – HIV has been linked to cognitive impairment, rabies is associated with hydrophobia, Brucella suis causes emotional disturbances, Leptospira has been shown to cause manic and psychotic symptoms, and Mycobacterium tuberculosis causes depression and anxiety. Campylobacter jejuni (C. jejuni), a bacteria common in foodborne illnesses, has also been shown to induce anxiety-like behavior and worsen inflammation in stressful conditions, an effect that was reduced when treated with the probiotic Lactobacillus farciminis (L. farciminis). Additionally, a certain balance of microbiota may influence the likelihood of whether IBS patients also suffer from depression. There was a lower prevalence of clinically significant depression in IBS patients with increased Firmicutes and decreased Bacteriodetes compared to patients with normal microbiota, while an increase of R. torques has been associated with increased severity of emotion and social dysfunction.
It is becoming clear that the health of the gut microbiota can not only be influenced by stress, but it can also play a role in each of the six contributing factors of Irritable Bowel Syndrome. So, if you suffer from IBS or IBS-like symptoms, rebalancing your gut microbiota will be another key step on your journey to better health.
There are now two very important steps to improving your health if you suffer from IBS – Managing Stress and Rebalancing Your Microbiota. Please stay tuned for the third and final installment in ELMTM | Maine to learn all about the proven nutrition and lifestyle changes you can make to get back to optimal health.
Stephanie Walsh, CPT, CNTP, CEPC is a Certified Nutrition Therapy Practitioner, Certified Eating Psychology Coach and Certified Personal Trainer. Contact Stephanie at (207) 730-2208 or email her: swalsh@theholistichealthapproach.com. www.theholistichealthapproach.com.
ELM™ | Maine
