Irritable Bowel Syndrome is a functional disorder of the gastrointestinal tract that causes pain, cramping, bloating, bowel movement disturbances, and a sensation of incomplete emptying of the bowel. IBS consists of three subtypes:
- IBS-C (constipation-predominant)
- IBS-D (diarrhea-predominant)
- IBS-M (mixed or cyclic bowel habits)
Researchers still don’t have a complete picture of the conditions and factors that lead to the manifestation of IBS, but a growing body of evidence suggests that the gut microbiome may play a role both in its pathophysiology, as well as in the alleviation of symptoms.
The Relationship Between Gut Microflora and IBS
The accumulation of clinical evidence across 10 years paints an emerging picture of the connection between gut microbiome disruptions, also known as “dysbiosis,” and the expression of IBS symptoms.
Several studies have demonstrated that patients with IBS have similar intestinal microorganism profiles. These profiles include high levels of bacteria that increase inflammation, like Enterobacteriaceae and Streptococcus species, and low levels of helpful bacteria, specifically Lactobacillus and Bifidobacterium species.
The microbiomes of patients who suffer from post-infectious IBS further support the hypothesis that dysbiosis plays a causal role in IBS. Affected individuals have a six times greater risk of developing IBS after a gastrointestinal infection. Researchers believe that antibiotics used to treat the infection have the unintended consequence of depleting helpful bacteria which leaves the colon vulnerable to an overgrowth of harmful bacteria.
Antibiotics like rifaximin have been shown to reduce IBS-related diarrhea, reinforcing the idea that pathogenic overgrowth plays a role in the manifestation of post-infectious IBS.
Probiotics as Treatment for IBS
Probiotics may improve IBS related symptoms and overall quality of life in the following ways:
- Correction of post-infectious lactose intolerance
- Reduction of bloating and gas
- Strengthening of the gut barrier via helpful bacteria
- Reduction of pro-inflammatory proteins that can disrupt intestinal motility
Nailing down the effectiveness of a particular probiotic strain for a specific IBS symptom is difficult due to the fact that there are a myriad of strains and strain combinations, and several subtypes of IBS, all with varying and transient symptom profiles.
That being said, Lactobacillus and Bifidobacterium are the most thoroughly researched genera, and they show the most promise in terms of symptom alleviation. Clinical trials have demonstrated the following positive treatment effects and their associated strains:
- Constipation and bloating: Bifidobacterium infantis, B. brevis and B. animalis
- Diarrhea, cramps, and bloating: Lactobacillus plantarum, L. casei, L. reuteri, and L. acidophilus
- Bowel frequency and motility issues: Bifidobacterium lactis, B. infantis, B. longum, Lactobacillus paracasei, and L. acidophilus
Studies have demonstrated the safety of Lactobacilli and Bifidobacteria mixtures to a degree of confidence that they can be an effective part of most medically supervised treatment plans for IBS management. Still, it is important that clinical research continues, including larger, more inclusive studies that can be generalized to the population as a whole, rather than individual populations such as the very young, or the very old.
Researchers are cautiously optimistic that ongoing trials will only add to the strong body of evidence that highlights the human microbiome as a key causal factor in the development of IBS, and probiotics as a key factor for improvement of symptoms.
Emerging Evidence for Single Strain Effectiveness
Reviews of past clinical trials have generally shown strain mixtures to be more effective at reducing symptoms. However, more recent studies are showing a positive effect using single strain Lactobacillus and Bifidobacteria species.
These new insights could be beneficial to patients who are experimenting to figure which supplements work best for their symptoms (taking some of the time and guesswork out of that process).
In a 2020 clinical trial, IBS patients were separated into three groups. They were given probiotic supplementation for eight weeks and then assessed for symptom severity:
- Group one received L. paracasei
- Group two received B. longum
- Group three received a placebo
After eight weeks, L. paracasei supplementation increased bowel movements in patients with constipation and decreased bowel movements in patients with diarrhea. L. paracasei and B. longum treatments lead to an increase in quality of life and emotional wellbeing compared to pre-treatment.
This study suggests that L. paracasei (on its own) may be an effective treatment for alleviating IBS symptoms in individuals of both IBS-C and IBS-D subtypes.
Choosing a Probiotic Supplement for IBS
As mentioned, a product that works best for your particular symptom profile may take some trial and error, but it’ll be worth it in the end.
Before taking any over-the-counter probiotic supplement, be sure to check the ingredient list. Some manufactured products contain fillers that may exacerbate IBS symptoms in certain people. These include oats, inulin, lactose, fructose, sorbitol, and xylitol.
Try only one product at a time, and stay with it for four weeks. This gives the probiotic time to exert an effect, and it gives you time to assess how it’s affecting your condition.
Single Strain or Multi Strain Probiotics?
Probiotic-containing products come in both single-strain and multi-strain variations. As the evidence suggests, probiotics that contain Lactobacillus and/or Bifidobacterium are the most likely to restore a healthy microbiome, so be sure to choose products with those genera.
You can try matching specific strains to your IBS subtype, or you can begin with a mixture. The important thing is that you stay with one treatment for the full four weeks.
It may also be helpful to keep a symptom journal, so you can have a clear picture of your condition’s trajectory. Do you feel better, worse, or the same?
Always take the appropriate dose as instructed by the product manufacturer, and make sure that the manufacturer has listed the number of live microorganisms the product contains. This is the CFU (colony forming units) number.
Final Thoughts on Probiotics and IBS
Probiotic supplementation can come from either food or dietary supplements. The two most important factors are:
- Matching strains and strain mixtures to your individual symptoms
- Ensuring live organisms at the time of consumption
Many commercial yogurt products contain Lactobacillus and Bifidobacteria, which make them a great natural source for supplementation.
Probiotics in the form of dietary supplements, on the other hand, don’t need to be approved by the FDA. Consumers must be well-informed and cautious when making decisions about purchasing an over-the-counter probiotic supplement.