The term IBS is used to describe chronic colon problems that occur in the absence of an identifiable medical cause. Common symptoms include alternating diarrhea and constipation, excess intestinal gas, intestinal cramping, uncomfortable bowel movements, abdominal discomfort following meals, and excessive awareness of the presence of stool in the colon. Despite all these distressing symptoms, in IBS, the intestines appear to be perfectly healthy when they are examined. Thus the condition belongs to a category of diseases that physicians call “functional.” This means that while the function of the bowel seems to have gone awry, no injury or disturbance of its structure can be discovered. (The analogous problem in the stomach is called dyspepsia, and the two conditions frequently overlap.)

Because the cause of IBS is not understood, conventional medical treatment of IBS is highly inadequate. One drug that had shown promise, Zelnorm, was withdrawn from the market for safety issues. Another, Lotronex, was temporarily withdrawn, and then re-approved, but only under strict limitations. Other medical treatment approaches for IBS include increased dietary fiber, drugs that reduce bowel spasm, and drugs to address constipation or diarrhea as needed. In addition, various forms of psychotherapy, including hypnosis, have been tried, with some success.1-6


Peppermint oil is widely used for IBS, and the evidence suggests that it is probably useful. A majority of placebo-controlledstudies have found peppermint oil to be more effective than placebo.7-12,34,49,64,67 However, most of these studies are small.

For more information, including dosage and safety issues, see the full Peppermint article.


Numerous double-blind trials indicate that various probiotics("friendly" bacteria) may be helpful for IBS.15,16,25,27,28,35,47,50,51,54-56,61,69,70

For example, in a 6-week, double-blind, placebo-controlled trial of 274 people with constipation-predominant IBS, in which constipation is a more significant symptom than diarrhea, use of a probiotic formula containing Bifidobacterium animalissignificantly reduced discomfort and increased stool frequency.50 Another study examined the effects of 4 weeks of treatment with L. plantarumon intestinal gas in 60 people with IBS. This study found benefits that persisted for an entire year after treatment stopped.15 In a review of 3 randomized trials, Lactobacillus rhamnosus GGwas associated with improvement in symptoms, especially a reduction in abdominal pain, among 393 children with IBS.72

In another randomized trial, 266 women with constipation who consumed yogurt containing B. animalisand the prebiotic fructo-oligosaccharide twice daily for two weeks experienced significant improvement in their symptoms compared to women consuming regular yogurt as a placebo.60

And finally, a 4-week randomized trial involving 122 people with IBS found evidence that B. bifidumimproved symptoms and quality of life compared to placebo.78

Benefits have also been seen in other smaller, double-blind trials, as well, using Lactobacillus plantarum,25, 27L. acidophilus,16,55L. rhamnosus,47L. salivarus,51,63 and B. infantis,51as well as proprietary probiotic combinations including various strains.28,35,54,62 One such combination, called VSL#3, contains B. longum, B. infantis, L. acidophilus, L. plantarum, L. casei, L. bulgaricus, and Streptococcus thermophilus. In a double-blind, crossover trial, 59 children aged 5-18 years old were randomized to receive VSL#3 or placebo for 6 weeks.69 After a 2-week "wash-out" period, the children were switched to the other treatment. VSL#3 was associated with a reduction in symptoms, including abdominal pain, bloating, and gas.

Of course, not all studies have supported the use of probiotics as a treatment for IBS.26,36,57 One randomized trial involving 90 people with diarrhea-predominant IBS found Saccharomyces boulardiito be more effective than placebo at improving quality of life.70But, the probiotic did not seem to improve the actual symptoms of IBS. Two studies that pooled previous randomized trials on the use of probiotics for IBS came to similar conclusions: probiotics appear to offer some benefit, most notably for global symptoms and abdominal discomfort. However, these two studies were unable to determine which probiotic species were most effective.58,59

Lactobacillus plantarum 299vfailed to provide significant improvements in abdominal pain, bloating, or quality of life when compared to placebo in a randomized trial with 81 adults over an 8 week period.83

Probiotics Lactobacillus, Bifidobacterium, Escherichia, and Streptococcus(alone or in combination) were evaluated in a review of 37 randomized trials. Priobiotics were associated with fewer global symptoms, abdominal pain, bloating, and flatulence when compared to placebo. There were no differences found in urgency-related symptoms. Although probiotic therapy appears effective, the right combination of strains remains unknown.82

For more information, see the full Probiotics article.


In a double-blind study, 55 people with chronic constipation caused by IBS received either ground flaxseed or psyllium seed (a well-known treatment for constipation) daily for 3 months.17 Those taking flaxseed had significantly fewer problems with constipation, abdominal pain, and bloating than those taking psyllium. The flaxseed group had even further improvements in constipation and bloating while continuing their treatment in the 3 months after the double-blind study ended. The researcher concluded that flaxseed relieved constipation more effectively than psyllium.

For more information, see the Flaxseed article.

Chinese Herbal Medicine

Chinese herbal medicine is traditionally practiced in a highly individualized way, with herbal formulas tailored to the exact details of each person’s case. In a double-blind, placebo-controlled trial, 116 people with IBS were randomly assigned to receive individualized Chinese herbal treatment, a “one-size-fits-all” Chinese herbal formulation, or placebo.29Treatment consisted of 5 capsules 3 times daily, taken for 16 weeks. The results showed that both forms of active treatment were superior to placebo, significantly reducing IBS symptoms. However, the individualized treatment was no more effective than the “generic” treatment. Similar results were seen in another study as well.44

In a review of 19 randomized trials with 1,510 people, Chinese herbal medicine was associated with a greater cure rate, and reduced recurrence of constipation-dominant IBS compared to traditional Western treatments. The Chinese herbal medicines focused on the liver and were given over a period of 3-12 weeks. However, there were many biases in the trials, which makes outcomes less reliable.80

For more information on this complex medical system, including important safety issues, see the Traditional Chinese Herbal Medicine article.