Probiotics: How Good Are These 'Good' Bacteria?

Deborah Flapan; Darbe Rotach

July 16, 2013


Probiotics have been advertised to help a variety of conditions, including irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD), and to prevent food allergies. To help you advise your patients on when probiotics may be an appropriate treatment, this slideshow examines current research to show the latest thinking in this area. Photo by Science Source

Slide 1.

Probiotics are bacteria that are either the same as or similar to microorganisms found naturally in the human body. Also referred to as "good bacteria," probiotics are available in the United States in oral products, such as dietary supplements and yogurt. Despite many health claims made on product packaging and in television ads, the US Food and Drug Administration has not approved probiotics for the treatment of any disease or condition, according to the National Center for Complementary and Alternative Medicine (NCCAM). Photo by Science Source

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Probiotics for Diarrhea in Irritable Bowel Syndrome
Probiotics are sometimes used to treat diarrhea caused by IBD and IBS. However, a recent study of probiotics to treat diarrhea associated with IBS found similar improvements among those who consumed probiotics compared with those who did not. While previous small studies have suggested some probiotic efficacy, the authors concluded that "This trial does not provide evidence for effectiveness of a probiotic in IBS." The study included more patients (n = 179) and a longer study period (12 weeks) than did previous research. (BMC Gastroenterol. Published online March 7, 2013.) Photo by Wikimedia

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Probiotics May Help Prevent Antibiotic-Related Diarrhea ‏
A review published May 31, 2013, in the Cochrane Database of Systematic Reviews found that probiotics are safe and effective for preventing Clostridium difficile–associated diarrhea (CDAD) in children and adults taking antibiotics. In 23 trials examined, enrolling a total of 4213 participants, probiotic use was associated with a significant 64% reduction in risk. On the basis of the overall evidence, the reviewers had moderate confidence in this large relative risk reduction. "Although probiotics are clearly superior to placebo or no treatment for preventing CDAD, further head-to-head trials are warranted to distinguish optimal strains and dosages," the review authors conclude. Photo by Thinkstock

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Probiotics During Pregnancy May Ward Off Eczema, Food Allergy
In research reported in the October 18, 2012, issue of the Journal of Allergy and Clinical Immunology, infants whose mothers took probiotics during pregnancy and while breast-feeding were less likely to develop eczema. The mothers all had a history of allergy, so their children were at high risk. About 30% of infants whose mothers took probiotics developed eczema compared with 79% of infants whose mothers did not. However, the study found no difference in the incidence of other allergies at age 2 years, including milk, wheat, soy, and dog and cat dander. And in a separate review published online April 17, 2013, the authors write, "Twenty-three randomized, placebo-controlled intervention studies regarding the clinical effect of probiotic supplementation on development of [food] allergy and eczema in particular have been published. Around 60% of the studies show a favourable effect decreasing the risk of eczema during the first years of life. The remaining studies fail to show an effect." Photo by Thinkstock

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Allergic Rhinitis Eased by Antihistamine + Probiotic

In other allergy research, supplementing the antihistamine levocetirizine with the probiotic Lactobacillus johnsonii EM1 effectively alleviated the symptoms of perennial allergic rhinitis in a group of Taiwanese children, according to a study published in the July 2012 issue of the International Journal of Pediatric Otorhinolaryngology. The study was somewhat small, with just 62 children. In addition, the "open-label design makes it difficult to compare the clinical response between the 2 treatment groups, but any bias may have been decreased by using the crossover method," the researchers write. Another issue to be resolved is whether the benefit will extend beyond 12 weeks. Photo by Thinkstock

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Probiotics Affect Brain Activity
A new study in the June 2013 issue of Gastroenterology provides the first evidence in humans that probiotics in the diet can modulate brain activity. In a proof-of-concept study using functional MRI, researchers found that women who regularly consumed probiotic-containing yogurt showed altered activity of brain regions that control central processing of emotion and sensation. (The study was funded by Danone Research.) Whether the effects are beneficial is still to be determined with further study, lead author Kirsten Tillisch, MD (pictured), associate professor, Oppenheimer Family Center for Neurobiology of Stress, David Geffen School of Medicine, University of California–Los Angeles, told Medscape Medical News. Photo provided by Kirsten Tillisch

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Probiotics Cut Risk for Hepatic Encephalopathy in Half
In another brain-related study, probiotics were effective in helping to prevent a first episode of overt hepatic encephalopathy in patients with cirrhosis compared with patients not receiving probiotics, researchers reported from the International Liver Congress in May 2013. This study involved patients with a low level of hepatic encephalopathy at worst and was therefore for prevention, not treatment, session moderator Isabelle Colle, MD, from Ghent University in Belgium, who was not involved with the study, told Medscape Medical News. She explained that the use of probiotics is "certainly not" standard for such patients at this point. In previous research, prebiotics have been shown to have a stronger effect than probiotics. (Aliment Pharmacol Ther. 2011;33:662-671, J Gastroenterol Hepatol. 2012;27:1329-1335.) Photo by Wikimedia

Slide 8.

Possible Cholesterol-Lowering Effects
A review of the research on cholesterol-lowering effects of probiotics showed conflicting results, with probiotics resulting in improved lipid profiles in some studies but not others. The authors suspect that the differences may be a result of different mechanisms of action, but more research needs to be done: "Recent research has indicated that probiotics appear to regulate the expression of the NPC1L1 protein, HMGCoA reductase, and 7α-, 27α-hydroxylase, but these mechanisms are still not fully understood," the authors write. (Clin Lipidol. 2012;7:501-507.) Photo by Science Source

Slide 9.

Probiotics and Infection Risk After Colorectal Cancer Surgery
And finally, Chinese patients who received probiotics both before and after colorectal cancer surgery experienced fewer infections after the operation, according to results of a study published online December 12, 2012, in the American Journal of Clinical Nutrition. Patients receiving probiotics also experienced significant decreases in bacterial translocation and intestinal wall permeability. However, an expert not associated with the study suggested that the results may not be generalizable to countries outside of China for several reasons, including differences in how the surgery was prepared for and performed. Photo by Thinkstock

Slide 10.

Conclusion: It Depends
Depending on the condition, probiotics may provide some relief or prevent disease, such as with antibiotic-related diarrhea, eczema in infants, or allergic rhinitis. The effect of probiotics on brain activity may still show clinical benefits when further research is conducted. It appears that probiotic therapy can induce measureable changes in brain activity and may reduce the risk for hepatic encephalopathy in patients with cirrhosis; however, whether probiotics provide additional benefits to the brain has yet to be determined. Similarly, probiotics' effects on lipid levels and infection rates after surgery also need more research. Most adverse effects with these agents are mild and occur rarely, according to the NCCAM, which suggests that probiotics may be a safe treatment option for many conditions. "However, the data on safety, particularly long-term safety, are limited, and the risk of serious side effects may be greater in people who have underlying health conditions," the NCCAM notes. Photo by Science Source

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Contributor Information

Deborah Flapan
Director, Medscape Medical News
Chicago, Illinois

Darbe Rotach
Senior Photo Editor, Medscape
New York City