The nervous system in our gut has been called the ‘second brain’. It is connected to our brain via sympathetic and parasympathetic pathways and has bi-directional activity. In simple terms, this is the gut-brain axis, and it works both ways. A review published in October 2021 discusses the roles of gut bacteria and intestinal cells in chronic pain, neuropathy and hyperalgesia (increased sensitivity or response to pain)1. It is important to note that many studies which explain pathways and signalling are carried out in mice. This is very common in cell signalling and in nutrition.
Gut bacteria signal to your nerves via gut cells
Enterochromaffin cells (EC cells) are only part of the complex story of the gut-brain axis however. This new review examines this signalling pathway in detail. EC cells line the digestive tract, sensing gut bacteria and other signals from the gut and pass messages through to our nerves. In this way, our gut bacteria may influence visceral pain, inflammatory pain, headache or migraine, neuropathic pain and therefore is a new target for pain relief2.
Beneficial bacteria for appropriate pain responses
Receptors on EC cells can detected short chain fatty acids produced by our beneficial bacteria. These are just one of the essential products that we depend on our bacteria to make to promote our health and wellbeing. Analysis of your beneficial bacteria can indicate how much short chain fatty acid producers you have. It can also indicate if you might be low in these important chemical messengers. Changes in the types and quantities of short chain fatty acids have been demonstrated in peripheral neuropathy pain and rheumatoid arthritis pain among others.
Dysbiosis or bacterial imbalance may promote pain
EC cells can also recognise molecular signals from unwanted microbes in our gut such as lipopolysaccharide (LPS toxin) released by bacteria, flagellin (a protein component of the outer membrane of bacteria) and other structural components. It is proposed that dysbiosis or imbalanced bacteria in the gut therefore plays a role in chronic pain and neuropathy.
Too much or too little serotonin is a problem
EC cells in the gut release serotonin and about 90% of the serotonin in our body is produced at the gut by these cells. Serotonin is sometimes called the ‘happy hormone’ in the brain as it helps to regulate mood. A variety of signals including dietary, gastric acid, bacterial or viral signals, mechanical stimulation and drugs can trigger serotonin production at these cells. Serotonin usually functions to promote good intestinal motility and in turn bacterial balance. However, when the stimulus is too much, excess serotonin can cause the release of inflammatory signals, excite nerves and cause pain.
Serotonin can trigger mast cell activation and degranulation which is important for inflammation, histamine intolerance and Mast Cell Activation Syndrome. It may also induce excess contractions in the gut leading to loose stools, cramps and ‘IBS’ symptoms. It is therefore important to control the production of serotonin at the gut. Selective serotoinin reuptake inhibitors (SSRIs) or serotonin noradrenaline reuptake inhibitors (SNRIs) are the most common medications used to treat neuropathic pain3.
Our gut bacteria may play a direct role in brain health
Studies in mice have shown that gut bacteria can structurally influence the nervous system and the brain. This includes effects on the permeability of the blood brain barrier and the function and connectivity of the amygdala. The amygdala plays a role in mood disorders, nerve regeneration diseases and chronic pain.
Can we target the gut bacteria to reduce pain?
Already we know that supplementing with certain strains of Lactobacillus and Bifidobacteria (beneficial bacteria) in mice can increase the pain threshold. Altered gut bacteria (dysbiosis) has been associated in large human studies with particular types of pain also e.g. low Bifidobacteria in knee joint pain. This is a fascinating link between your gut bacteria and pain from perhaps anywhere in your body. Assessing your levels of beneficial bacteria and addressing dysbiosis could play a role in pain management in chronic pain, inflammation and neuropathy.
Is your gut related to your chronic pain disorder?
If you have IBS or digestive symptoms such as constipation or diarrhoea, bloating, flatulence cramps, pain or discomfort, it could be that the bacteria in your gut are out of balance. We have also seen in a number of patients with chronic inflammatory conditions, that even in the absence of digestive issues, there can be low beneficial bacteria in the gut. This might have been caused by stress, history of antibiotics or other medications such as proton pump inhibitors (PPI) or acid reflux medication. In addition we have seen an increase in the number of patients who have altered gut bacteria because they are following a restricted diet such as gluten free or grain free, keto, paleo, low FODMAP or other diets. If you want to know whether your gut bacteria is related to your chronic pain disorder the GI Ecologix test might be very helpful for you.
If you would like more information about the services we offer, including testing, please get in touch.
- Xu et al (2021) Enterochromaffin Cells: Sentinels to Gut Microbiota in Hyperalgesia? Front in Cellular and Infection Microbiology 11:1014
- Xu et al. (2021). Fecal Microbiota Transplantation: A New Therapeutic Attempt From the Gut to the Brain. Gastroenterol. Res. Pract.6699268
- Lee at al (2010) A review of SSRIs and SNRIs in neuropathic pain. Expert Opin Pharmacother11(17):2813-25.