Are Probiotics Helpful In IBS?

Microbiome Modulation for IBS

Dysbiosis is closely linked to Irritable Bowel Syndrome (IBS) and there is evidence that modulation of the microbiome can target IBS root causes and alleviate symptoms. While AGA clinical guidelines do not recommend probiotics for most conditions, including IBS, probiotic supplementation is generally considered safe by the public. Recent studies seek to assess how probiotic, prebiotic, fermented foods, polyphenols and foods with resistant starch may support increased abundance and resilience of beneficial (commensal) microbes in patients with dysbiosis, though evidence to support their use remains limited to date.

 

Demystifying Dysbiosis

Microbes, including bacteria, play an important role in physiological health. While humans have just 20,000 chromosomal genes, the human microbiome has an estimated 2-20 million genes [1]. These bacteria play a vital role in maintaining balance within the gastrointestinal (GI) tract and decreased diversity, abundance and resilience of the microbiota increases risk for GI complications [2,3].

The prevalence of dysbiosis in IBS is estimated at 73%, compared to 16% in healthy adults [4]. A sub-optimal microbiome is associated with increased production of hydrogen gas, indoles, phenols and other compounds that contribute to IBS pathogenesis and symptoms [3]. Resolution of dysbiosis helps reduce intestinal permeability by improving mucosal barrier function, which prevents pathogens from entering through tight junctions [5]. Reestablishing a healthy microbiome can also reduce IBS symptoms and help alleviate the psychological toll IBS poses [2]. 

 

Microbiome Modulation

The Rome Foundation acknowledges that manipulation of the microbiome may help re-establish the bidirectional gut-brain axis communication pathway and promote intestinal integrity and motility [6]. A healthy intestinal bacteria composition is generally 64% Firmicutes, 23% Bacteroidetes, 8% Proteobacteria and 3% Actinobacteria, while IBS patients show increased abundance of Firmicutes and reduced abundance of Bacteroides [3,4] Among patients with IBS-D and IBS-M, a lower abundance of butyrate-producing bacteria has also been observed [3,4]

Probiotics are viable microorganisms that have a beneficial effect on their host when taken in adequate amounts. Probiotics have the potential to promote a healthy balance of microbiota and support the innate and adaptive immune responses. Among IBS patients, probiotics can help reduce pain, symptom severity, bloating, distension, diarrhea, constipation, visceral hypersensitivity and inflammation and promote motility and barrier function [7]. In research, probiotics have also been shown to support the proper digestion of food and toxins, facilitate the production of vitamins made in the gut and promote the migrating motor complex (MMC), which helps prevent leaky gut [8].

 

Choosing a Probiotic

Probiotics are available as capsules, powders or chewable tablets and common strains include Bifidobacterium, Lactobacillus, Streptococcus thermophilus, Saccharomyces, and Bacillus species. Products may contain a single species or a mixture and the combination of species can influence their impact. When choosing a product, look for those that contain live and active bacteria and list CFU counts. Some probiotics may also be designed with a gastric acid protection which can help ensure probiotics arrive intact in the intestine. Probiotics are best taken just before bed to prevent bacteria from remaining in the stomach or small intestine with food and to allow the bacteria time to reach the colon overnight.

When working with patients with IBS, seek strains of probiotics that have been shown to help with IBS management. For example, Lactobacillus salivarius, L. plantarum, and L. acidophilus. Bifidobacterium strains have been shown to help alleviate IBS symptoms [9,10]. There is also evidence that a multispecies probiotic is more effective than a single-strain product [11]. The probiotic market is large and not all products are high-quality, so proper research into product quality is vital. Manufacturers are required to list the total weight of probiotic bacteria, which includes both live and dead microorganisms, so look for the number of CFU at the end of the product’s shelf life, not at the time of manufacturing [12]. Not all probiotics need to be refrigerated and many freeze-dried, moisture-protected capsules can be effective. Reference a reliable database that offers scientific-based information on products, doses, and formulation for specific conditions.

 

Prebiotics 

Prebiotics feed commensal bacteria and can be an effective means to reduce dysbiosis and promote intestinal health [3,4]. Prebiotics are naturally found in fruits and vegetables and are also available as supplements. Many prebiotic rich foods are high in fructo-oligosaccharides, galacto-oligosacchadies, inulin, beta-glucan and arabinogalactan, all FODMAPs. Low FODMAP options for patients include acacia fiber and partially hydrolyzed guar gum.

 

Other Foods for Microbiome Health

Notably, not all commensal bacteria are available as a probiotic. Akkermansia Muciniphila and Faecalbacterium Prausnitzii, a butyrate producing bacteria, are associated with reduced intestinal permeability, reduced inflammation and lower levels of toxins produced by pathogenic bacteria [13]. However, growth of these strains needs to be promoted through foods. 

Fermented and polyphenol-rich foods and supplements promote commensal bacteria growth, such as those listed above and others. Ginger and quercitin supplements provide large doses of polyphenols while good food sources include cranberry, pomegranate, berries and dark chocolate [14]. Resistant starch, which arrives intact in the colon and also feeds commensal bacteria, can be found in carbohydrate-containing foods that are cooked and eaten once cooled such as potato, beans, legumes and rice.

Further, while adding a probiotic pill or powder may be a convenient and easy (though somewhat pricey) way to introduce specific bacteria strains, fermented foods with live bacteria may be a more nutritious option, as they’ll provide protein, vitamins and minerals, too. The live probiotics in yogurt, kefir and certain cottage cheeses are known to survive intestinal transit, while shelf-stable, pasteurized products like kimchi and sauerkraut contain few to no live microbes. Notably, the FODMAP content of some foods also changes following fermentation. For example, raw cabbage is low FODMAP, while the same amount of cabbage as sauerkraut is high in the FODMAPs polyol and mannitol. Conversely, goat milk, soybeans, and wheat become low FODMAP following fermentation.

 

Summary

The link between microbiome health and IBS is complex and not fully understood. It remains unclear if the link between microbiome health, probiotics and fermented foods is related to the impact microbes have on overall microbiome composition or is a result of other mechanisms, such as modulation of the immune response or digestive processes. 

Diet and lifestyle interventions, such as prioritizing diverse, fiber-rich plant foods, remain a first-line intervention to promote a healthy microbiome, including for those with IBS. The importance of stress management, regular exercise, smoking cessation, and limiting intake of processed sweets, convenience foods and alcohol should not be overlooked, either. Still, there is reason to continue evaluating evidence that specific strains, along with prebiotics and other functional foods, can support the growth of commensal bacteria and potentially promote symptom relief in those with dysbiosis [15].