What causes IBS?
Irritable bowel syndrome (IBS) is a common digestive condition that affects approximately 12% of the global population. The common symptoms of IBS are outlined in the ROME IV criteria which outline IBS symptoms.
These IBS symptoms include:
- Changes in the stool consistency
- Abdominal pain
- Changes in the frequency of bowel movements
Additional symptoms such as bloating, and distention are also common in IBS. [Source: Pubmed]
Rather than there being a single cause of IBS, there are several factors that can contribute to IBS development.
These causes of IBS can include:
- Alterations in the gut-brain connection
- Food sensitivities
- Gut bacteria imbalances
- Low-grade inflammation
- Increases sensitivity in the nerves in the gut [Source: MDPI, Pubmed]
A key factor that is understood to contribute to IBS symptoms is the balance of the gut microbiome. Imbalances in the gut microbiome is termed dysbiosis and is commonly seen in IBS. This can be caused by long-term dietary patterns as well as the use of medications such as antibiotics. [Source: Pubmed]
Do antibiotics damage the gut?
As well as increasing the risk of developing IBS, the use of antibiotics in early life is also associated with the development of obesity, autoimmune diseases and allergic conditions.
The impact antibiotics have on the gut microbiome can depend on the type of antibiotic as well as the dose and duration it’s taken for.
The antibiotic Vancomycin has been shown to alter the balance of the gut microbiome leading to an increase in pathogenic species such as Klebsiella, Escherichia, and Shigella and reducing the beneficial Bacteroidetes species. [Source: Pubmed]
Clindamycin usage has been shown to reduce the diversity of the organisms in the gut microbiome and a reduction in beneficial species such as Roseburia, Lachospira, Coprococcus, Dorea, and Ruminococcus.
Broad-spectrum antibiotics that include ciprofloxacin, vancomycin, and metronidazole, promote the growth of less beneficial Streptococcus and also reduce the numbers of beneficial short-chain fatty acid-producing bacteria Bacteroides, Subdoligranulum, and Faecalibacterium.
These studies report that the gut can return back to its original balance after 8-31 months however, the microbiome can often remain changed from its original state. [Source: Pubmed]
The result of antibiotic usage on the gut microbiome was summarised in a 2019 report that found that the majority of antibiotics increase the levels of less beneficial gut bacteria. These less beneficial bacteria include Citrobacter spp., Enterobacter spp., and Klebsiella spp which contain molecules that promote inflammation in the gut.
Antibiotics also lead to other profound changes in the intestinal microbiota. These changes include a decrease in bacterial diversity, changes in the abundance of important beneficial bacteria and an increase in antibiotic resistance.
This can deplete levels of beneficial gut bacteria (such as Lachnospiraceae, Ruminococcaceae, and Clostridium scindens) which may promote the growth of pathogens such as Clostridium difficile, and Enterococcus. [Source: Pubmed, Pubmed]
Does taking antibiotics cause IBS?
Studies have found that antibiotics are a risk factor for developing IBS. In the 4 months after antibiotics, the risk of developing IBS is 3 times higher than it would have been without antibiotics. [Source: Pubmed]
This can be seen more so in the following 2 types of antibiotics, macrolides and tetracyclines.
- Macrolides include: Azithromycin, clarithromycin, and erythromycin
- Tetracyclines include: tetracycline, doxycycline, minocycline, tigecycline. [Source: Pubmed, Pubmed]
Antibiotics can lead to changes in the gut microbiome that may then lead to IBS. These changes can include a reduction in the good bacteria and an increase in the bacteria that have a negative impact on the gut. The combination of these factors may then reduce the stability of the gut microbiome and increase the risk of IBS.
The specific changes that can be seen after antibiotics are reduced diversity in the gut microbiome. Since the diversity of the gut microbiome is an indicator of how stable and resilient the gut is, a reduction in diversity indicates that the gut is more susceptible to further changes that can promote IBS symptoms.
Reductions in key beneficial bacteria have also been reported after antibiotics. This includes the gut bacteria F. prausnitzii and Bifidobacterium. F. prausnitzii is one of the most abundant bacteria in the gut and helps to reduce inflammation and the immune system in the gut while Bifidobacterium helps to crowd out pathogenic bacteria and regulate the immune system. The combined effect of the reduction in the 2 key bacterial groups can make the gut less resilient and more likely to infections and inflammation.
This is seen further by the overgrowth of the inflammation-promoting Enterobacteriaceae family of bacteria. This group includes pathogenic bacteria Escherichia, Shigella, Klebsiella, and Enterobacter. These proinflammatory bacteria may contribute to low-grade inflammation in the gut wall, a key factor in IBS. [Source: Pubmed]
The duration of changes in the gut bacteria depends on the antibiotic being used.
- Ciprofloxacin leads to a one-year change in the gut microbiome.
- Clindamycin leads to a two-year change in the gut microbiome.
- Clarithromycin plus metronidazole leads to a four-year change in the gut microbiome. [Source: Pubmed]
Also Read: How Long Does IBS Last?
Do antibiotics cause leaky gut?
Antibiotics have been shown to lead to an increase in the permeability of the gut lining. This is often referred to as leaky gut.
How antibiotics cause leaky gut is understood to be due to changes in how certain enzymes in the gut are broken down and processed. In particular, protease enzymes (which are released from the pancreas) come into contact with the gut lining.
Without antibiotics present, these enzymes that digest protein, are broken down by the gut bacteria and do not come into contact with the gut lining. However, as antibiotics deplete the gut bacteria these proteases may be present in high amounts and come into contact with the gut lining, triggering a change in gut health. [Source: Pubmed]
Via similar mechanisms, antibiotics may also contribute to the IBS symptom of visceral hypersensitivity. This is the increased sensitivity of the news along the lining of the digestive tract which results in pain and discomfort. [Source: BMJ]
In susceptible individuals, this impact can trigger a vicious cycle. Here, a short period of increased permeability can allow the immune system closer access to the microbes in the gut, leading to immune activation. This may then increase the permeability further. [Source: Pubmed]
This was seen to a greater extent when the antibiotics levofloxacin and metronidazole were prescribed. A less obvious change in the gut was seen after the use of Rifaximin, an antibiotic often prescribed for SIBO. [Source: Pubmed, Pubmed]
Can I take probiotics with antibiotics?
The beneficial yeast probiotic Saccharomyces boulardii, has been studied alongside antibiotics. This probiotic has been shown to reduce the risk of developing diarrhoea that is caused by antibiotics.
The benefit of using the probiotic was seen when it was started early in the course of antibiotic treatment. However, the continuation of its use, once the course of antibiotics was completed, did not lead to an increased benefit.
Studies have indicated that the effective dose of Saccharomyces boulardii is between 250mg and 1,000mg per day. [Source: Pubmed]
Additional probiotics have also been studied with positive results in reducing antibiotic-associated diarrhoea. These specific species of probiotics include:
- B. licheniformis,
- B. longum
- L. acidophilus
- L. casei
A dose-dependent benefit was also noted with doses of greater than 10 billion CFU providing the most protection.
The way probiotics can help reduce the side effects of antibiotics include:
- To temporarily colonise the gut preventing the adherence of opportunistic gut bacteria
- Lower the gut pH, making it a less favourable environment to pathogenic bacteria
- Preventing the binding of bacterial toxins to the gut lining.
- Increase the strength of the immune system in the gut. [Source: Pubmed]
Best antibiotics for IBS and SIBO?
SIBO (small intestinal bacterial overgrowth) is a condition where a higher level of bacteria is present in the small bowel that is considered normal. This overgrowth may be present in up to 78% of those with IBS.
Symptoms of SIBO include what is typically seen in IBS. These symptoms of SIBO include:
- Bloating
- Distention
- Abdominal pain
- Diarrhoea [Source: Pubmed]
Once SIBO is diagnosed via a SIBO breath test, part of the approach to treat SIBO can include antimicrobials to modify the gut microbiome.
One approach for this is the antibiotic Rifaximin. This antibiotic that is used for SIBO is poorly absorbed from the gut meaning that it does not enter general circulation which reduces the risk of systemic toxicity or side effects. [Source: Pubmed]
A characteristic of rifaximin is that it is soluble in bile. Since bile is reabsorbed and recycled at the end of the small intestine, this means that rifaximin does not enter the large intestine in high amounts. As a consequence, rifaximin is more effective in the small intestine and has minimal impact in the large intestine. [Source: Pubmed]
Rifaximin may also have an anti-inflammatory effect on the gut and increase friendly gut bacteria such as Bifidobacteria and Faecalibacterium prausnitzii making it a unique antibiotic. [Source: Pubmed] Rifaximin has also been proposed to treat dysbiosis (a general imbalance in the gut bacteria) as well as SIBO (an overgrowth). [Source: Pubmed]
Historically, broad-spectrum systemic antibiotics were used to treat SIBO but there are associated with greater side effects. These antibiotics include; fluoroquinolones, metronidazole, tetracycline, amoxicillin-clavulanic acid and chloramphenicol.[Source: Pubmed]
The side effects from these antibiotics include; headache, nausea, dizziness, dyspepsia, abdominal discomfort, abdominal distention, diarrhoea, constipation and flatulence. [Source: Pubmed]
How to treat IBS and SIBO naturally
A 2017 analysis concluded that probiotics are effective at treating SIBO. This was seen in a reduction in symptoms as well as through SIBO test results. A further improvement was seen with the use of probiotics alongside antimicrobial therapies. [Source: Pubmed]
Herbal antimicrobials have been studied alongside rifaximin. A 2014 study concluded that antimicrobial herbs were as effective as antibiotics in treating SIBO. The herbs included in the antimicrobial formulas used in the study include:
- Oregano oil
- Thyme
- Lemon balm
- Coptis
- Pau D’arco [Source: Pubmed]
In addition to this study, research has also shown that other herbs have the ability to support the balance of the gut microbiome. These herbs include:
- Garlic (allicin) [Source: Pubmed]
- Neem [Source: Pubmed]
- Clove oil [Source: Pubmed]
- Peppermint oil [Source: Pubmed]
Alongside antimicrobials, probiotics and prebiotics have been shown to increase how well these approaches work at reducing the levels of bacteria in SIBO. [Source: Pubmed, Wiley]
Finally, the low FODMAP prebiotic fibre PHGG (partially hydrolysed guar gum) was shown to improve the eradication of SIBO. This was seen in results where the eradication rate of SIBO was 62% when only antimicrobials were used, versus an eradication rate of 87% when PHGG was used alongside antimicrobials. [Source: Pubmed]
What to do if you get diarrhoea while on antibiotics?
Diarrhoea is a common side effect of antibiotics that can occur in up to 30% of those treated with antibiotics. This can occur during the course of antibiotics or up to 2 months after the course has ended.
Diarrhoea from antibiotics is understood to take place due to the way antibiotics cause imbalances in the gut bacteria. This can include Clostridium difficile infections which can be responsible for up to 25% of cases.
Other organisms that can contribute to antibiotic-associated diarrhoea include; C perfringens, Staphylococcus aureus and Candida spp as well as alterations in carbohydrate and bile digestion. [Source: Pubmed]
Diarrhoea and antibiotics
The antibiotics that are more likely to cause diarrhoea include aminopenicillins, clavulanate, cephalosporins, and clindamycin. Additional factors include being aged over 65, immunosuppression, being in an intensive care unit, and prolonged hospitalisation all increasing the risk of diarrhoea from antibiotics.
If the diarrhoea is severe a doctor may prescribe a replacement antibiotic with fewer side effects. The antibiotics with a lower risk of causing diarrhoea include; quinolones, co-trimoxazole, or aminoglycosides. In addition to this rehydration may be required to replace electrolytes lost via loose stools.
Common advice is that medications that slow the gut should be avoided. This includes medications such as loperamide (Imodium). This is due to these medications slowing the gut down and preventing the toxins produced by potential bacterial infections from being excreted effectively through the stool. [Source: Pubmed]
Additionally, as already mentioned probiotics (such as Saccharomyces boulardii) have been shown to help reduce these side effects of antibiotics. [Source: Pubmed]
Consultation
While antibiotics can be an important treatment for infections, they can lead to side effects such as diarrhoea. For many, these symptoms will resolve shortly after the antibiotics have ended.
However, there are some who then go on to develop IBS. This can be due to changes in the balance of the bacteria as well as alterations in the gut lining and the immune system in the gut.
Rebalancing the gut can involve dietary changes and the introduction of natural supplements.
To read more about this natural approach to IBS read our blog ‘How to Cure IBS’.
