Bifidobacterium, courtesy CDC/Bobby Strong

Irritable bowel syndrome (IBS) is a chronic gastrointestinal condition associated with abdominal pain and changes in bowel movements. It affects approximately 12% of the population, and in practices devoted to abdominal and pelvic pain (like my own), up to a 1/3 of patients have IBS. Irritable bowel syndrome is subclassified based on “typical” bowel movements: constipation (IBS-C), diarrhea (IBS-D), and both diarrhea and constipation (IBS-M).

Some studies suggest that abnormal bacterial growth in the intestines may have a role in IBS. For these reasons some providers recommend probiotics and many patients take them. Is there any medical evidence to support this practice?

FIrst of all, what are probiotics? According to the National Center for Complementary and Allopathic Medicine, probiotics are live bacteria similar to the beneficial microorganisms that we have in our body (typically our gut, but we have “good” bacteria in the vagina as well).

There are 2 good studies that have looked at probiotics, specifically Bifidobacterium. One study looked at outcomes with Bifidobacterium infantis and found that a dose of 1 x 108 CFU/mL  daily helped symptoms approximately 20% better than the placebo with no adverse events. Another study looked at  B. bifidum MIMBb75 versus placebo, and the patients randomized to the probiotic showed statistically significant improvement in health-related quality of life. This probiotic was also well tolerated and adverse events did not differ from placebo.

One important thing to consider with IBS is the placebo response rate is as high as 59%, so results must always be interpreted with caution. These 2 studies with Bifidobacterium are more useful than most probiotic studies because they are randomized and there is a placebo arm.

Studies with Lactobacillus spp. have not been encouraging for IBS.

So is it worth trying Bifidobacterium? It might be. The studies tell us symptoms improve within 2 weeks, so for people who want to try it don’t buy a truck load. Get a 4 week supply and keep a diary, paying attention to pain, bloating and bowel movements. If after 2-3 weeks you feel better, you have your answer.

As other probiotics have been largely underwhelming for IBS in the literature, it’s a good idea to stick with what has at least in 2 studies (smallish, but well done) has shown to be better than placebo: Bifidobacterium infantis or B. bifidum.

There is no allopathic medicine and there is no alternative medicine. There is only evidence based medicine.



Remember, this post is not direct medical advice.


Whorwell PJ, Altringer L, Morel J, et al. Efficacy of an encapsulated probiotic Bifidobacterium infantis 35624 in women with irritable bowel syndrome. Am J Gastroenterol. 2006;101:1581-1590. 23.

Guglielmetti S, Mora D, Gschwender M, et al. Randomised clinical trial: Bifidobacter bifidum MIMBb75 significantly alleviates irritable bowel syndrome and improves quality of life- a double-blind, placebo-controlled study. Aliment Pharmacol Ther. 2011;33:1123-1132.

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