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Probiotics and Prebiotics


Gut microbiota are microorganisms, mainly bacteria, living in our gut. Bacteria in the gut have a variety of important physiological functions, from vitamin synthesis to breaking down (fermentation) of dietary fiber. Bacterial fermentation of fiber leads to the production of short-chain fatty acids (SCFA) that not only positively affect gastrointestinal health but can also regulate the immune system (and thus impact our general wellbeing). There has been an explosion of interest in the gut flora recently, mainly because of the findings that suggest various ways in which our health may be altered by these microorganisms. The success of the fecal microbiota transplantation (FMT, transfer of stool from a healthy donor to a patient) in the treatment of recurrent Clostridium difficile infection, has also surely contributed to the excitement surrounding the employment of bacteria in treating various diseases. 


Comparisons of gut bacteria between healthy subjects and people with certain conditions (irritable bowel syndrome, asthma, diabetes) showed significant differences. However, at this point, it is not clear whether these differences are the cause or the consequence of the underlying conditions. Nonetheless, an unhealthy microbiome is now being associated with a range of disorders, including autism, allergies, atherosclerosis, and metabolic syndrome. 


Gut microflora depends on a number of factors, such as diet, medications, geographical location, and environmental aspects. An easy and efficient way to modify the structure and function of the gut microflora is through diet. Gut microorganisms rapidly (within a single day!) respond to dietary alterations.   Interestingly, new research implies that microbes may be able to manipulate our dietary choices in ways that make us crave food that the bacteria themselves are thriving on. Although further research is needed, this presents an exciting possibility: breaking unhealthy eating habits (and achieving a healthy weight!) through modification of microflora.





Prebiotics and probiotics for IBS relief

Microflora can be altered not only by diet but also through the use of probiotics and prebiotics. Probiotics are defined as live microorganisms which, when administered in adequate amounts, may confer health benefits on the host. Beneficial microorganisms can be obtained from fermented foods (kimchi, yogurt, sauerkraut, kombucha) and by using probiotic supplements. Prebiotics are substances, mostly carbohydrates, used by these beneficial microorganisms as food. They, too, can be acquired through proper diet and from prebiotic supplements. Generally, clinical studies that investigated the usefulness of probiotics and prebiotics were focused on the supplements rather than the food sources. Although there is a lot of excitement about the potential of probiotics and prebiotics for treating various conditions, many questions about their use (correct dosing, lengths of therapies, choices of strains, etc.) still remain unanswered.

Nonetheless, various studies show promise regarding the use of probiotics in the treatment of several conditions such as irritable bowel syndrome (IBS), ulcerative colitis, constipation, acute diarrhea and others.   The role and proper use of prebiotic supplements to selectively enrich specific bacterial strains are not clearly defined. A balanced, diverse and healthy diet that provides a wide spectrum of prebiotics will offer broader support to the gut microorganisms than any particular prebiotic supplement. 


Probiotics and Prebiotics in Irritable Bowel Syndrome (IBS)


The most recent review of existing clinical studies found probiotic supplements to be effective in reducing symptoms of IBS.   The strains of bacteria that showed most promise were: Bifidobacterium infantis 35624, Lactobacillus plantarum and Bifidobacterium bifidum.


On the other hand, there is no consensus in the scientific literature about the use of prebiotic supplements in IBS. Although there are studies that report some improvement in IBS symptoms, it is clear that the proper use of prebiotic supplements is still largely unknown. For example, in several studies increased doses of prebiotics resulted not in better outcomes, but in the worsening of the symptoms. In our opinion, before further data is made available, it is best to obtain prebiotics from food (fruits and vegetables are a great source of dietary fiber and thus prebiotics), or from those supplements that contain both probiotics and prebiotics. Such supplements also called synbiotics, contain prebiotics in low enough doses not to pose the risk of worsening the IBS symptoms, but in sufficient enough doses to help the bacteria that are also included in the supplement thrive. 


How to Use


General recommendations for how to best use probiotics are hard to make. Studies to date did not produce uniform findings in that regard. Our recommendation is to choose probiotics that contain specific strains of proven beneficial bacteria. The number of bacteria that is needed for a particular health benefit has not been firmly established.  Try different numbers (but remember, bigger is not always better) and evaluate their effects on your symptoms.

Optimal lengths of probiotic therapies are not clear either, but there are indications that the bacteria that are taken as supplements do not become permanently established in the gut flora. This suggests that, if continuity of the beneficial effect is to be ensured, supplements ought to be taken on a regular basis.


As mentioned, another way of enriching your gut flora is by eating fermented foods such as kimchi, sauerkraut, pickled fish, kefir, miso, kombucha. These foods contain various live cultures of bacteria that contribute to the diversity and function of the gut flora. Try different fermented foods and see if any of these improve your symptoms. An excellent book that contains a wealth of information about the science and methods of fermentation is "The Art of Fermentation” by Sandor Ellix Katz.




Most commonly, only mild side effects, such as gas and bloating, are associated with the use of probiotics. Although generally considered safe in the healthy population, probiotics can potentially be harmful in immune-compromised people, patients with resected intestines and serious health conditions.   


Probiotic Supplements for IBS


We found the following probiotic supplements to contain bacterial strains that show promise in IBS.  


  • Align Probiotic supplement 24/7 Digestive support, containing single strain Bifidobacterium infantis 35624

  • Hyperbiotics Pro-15, containing 15 strains including L. plantarum and B. infantis

  • Jarrow formula, Jarrow-Dophilus, containing multiple strains including L. plantarum and B. longum

Last updated: August 16, 2016

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