Probiotics are live microorganisms that when administered in adequate amounts confer a health benefit on the host. The gut microbiota is thought to be involved in the pathogenesis of multiple gastrointestinal disorders, including IBS. The goal of using probiotics in IBS is to modify the microbiota and, in doing so, alter fermentation, gas production, and absorption. In general, studies involving probiotics have been of low methodological quality due to small numbers of patients, a variety of probiotic agents used, and short follow-up periods. In a systematic review of 19 studies evaluating a variety of individual and combination probiotic products in patients with IBS, the conclusion was that probiotic use generally results in modest improvement in overall symptom burden. A second systematic review found evidence for use of Bifidobacterium infantis 35624 in providing benefit in the composite symptom score of IBS patients on the basis of two appropriately designed clinical trials. In one study, 362 women were randomly assigned to groups that received doses of B. infantis at 1 × 10⁶, 1 × 10⁸, or 1 × 10¹⁰ colony-forming units (CFUs) per day or placebo for 4 weeks. Only the 1 × 10⁸ CFU dose was found to provide benefit compared to placebo, significantly improving abdominal pain and secondary measures. Randomized studies of B. animalis and B. lactis in conjunction with yogurt starters have found significant reductions in abdominal distention and IBS symptoms. A probiotic product containing a combination of seven different probiotic organisms (VSL#3; three bifidobacteria, three lactobacilli, and one streptococcus) has been shown to significantly improve bloating compared with placebo. Further studies are needed to confirm these findings and establish optimal doses and duration of therapy.

Prebiotics are distinct from probiotics in that they are nondigestible food ingredients that beneficially affect the host by selectively stimulating the growth and/or activity of one of a limited number of potentially health-promoting bacteria in the colon. Prebiotics are thought to act by stimulating the growth of beneficial commensal microbes, resulting in an increase in vitamin and mineral absorption, improved digestion, and increased protection against viruses, fungi, and damaging bacteria. They may also act by increasing the amount of short-chain fatty acids and lactic acid-producing bacteria and activating carbohydrate receptor immune cells. A randomized, placebo-controlled clinical trial of the prebiotic trans-galacto-oligosaccharide (GOS) in IBS found that, compared with those receiving placebo, patients taking the prebiotic had improvements in stool consistency, bloating, and flatulence. A dose of 3.5 g/day was most successful in this study. Another study focusing on optimal dose of prebiotics found that patients ingesting 10 g/day of short-chain fructo-oligosaccharide (scFOS) for 7 days exhibited the greatest increase in fecal bifidobacteria counts while minimizing side effects, such as abdominal cramps, excess flatus, and bloating.

Acupuncture is part of traditional Chinese medicine that has been practiced for thousands of years. In contrast, its use in Western society has only recently become more common and better accepted. In traditional Chinese medicine, acupuncture is believed to rebalance the “qi,” the energy or life force in the body that runs through meridians, by penetrating the skin with solid, thin, metallic needles at specified acupoints, manipulated by hand or electric stimulation. While the exact mechanism whereby acupuncture may improve gastrointestinal symptoms is not known, acupuncture has been shown to influence visceral reflex activity, gastric emptying, and gastroesophageal reflux. Specifically, in IBS, acupuncture has been suggested to alter visceral sensation and motility by stimulating the somatic nervous system and the vagus nerve. Several high-quality, randomized, controlled studies have evaluated the efficacy of acupuncture in IBS. Schneider and colleagues randomized 43 patients with IBS to either acupuncture or sham acupuncture (i.e., a non-penetrating needle). There was no significant difference in quality of life ratings between subjects in each group; however, there was a significant improvement from baseline symptoms in both groups. Another recent study by Lembo and colleagues compared the effects of acupuncture, sham acupuncture, and no treatment (control) in relieving patients’ IBS symptoms. No significant difference in global IBS symptoms was found between the acupuncture and sham groups; however, both of those groups demonstrated a significant effect on overall improvement in IBS compared to the waitlist control group. The results of these studies suggest that both acupuncture and sham acupuncture are effective in alleviating IBS symptoms compared to a waitlist control. These studies do not exclude the possibility that it is the ritual of acupuncture that is responsible for this positive effect.