Does it work? Can St Johns Wort help irritable bowel syndrome?


BACKGROUND: St John’s wort is one of the better known herbal remedies. Evidence continues to mount that it is effective in treating mild to moderate depression. Debate continues over how best to regulate the herb, which in Ireland is available only by prescription.

At the same time, research continues to establish whether St John’s wort may be effective for other conditions, including irritable bowel syndrome (IBS). This condition is a relatively common source of abdominal pain and other bowel problems.

While the symptoms vary widely, they can be both severe and embarrassing. For this reason, IBS is associated with depression, although much remains unknown about their connection. What has been shown, however, is that pharmaceutical anti-depressants can relieve IBS symptoms.

Since surveys show that people with IBS frequently use herbal remedies, interest has developed in whether St John’s wort might relieve IBS symptoms. This year saw the first studies in this area, but the results have not lived up to expectations.


The first randomised controlled trial in this area enrolled 70 patients with diagnosed IBS. Participants took either 900mg St John’s wort daily or placebo. After 12 weeks, symptoms such as pain and bloating, and an overall IBS symptom score, had improved in both groups. However, those taking the placebo had more improvements than those taking St John’s wort. This applied to the overall IBS symptom score, and for diarrhoea, pain and bloating.

A second study enrolled 30 women with IBS who took 900mg St John’s wort for eight weeks. The primary focus here was on anxiety, depression and IBS symptoms of pain and bloating. Significant improvements were found. However, this study did not include a placebo group. Given that the placebo group in the first study did better than the St John’s wort group, this study does not help determine whether St John’s wort is better than placebo for IBS patients.


These studies, like most others, found that those taking St John’s wort had few adverse effects. However, numerous drug interactions have been reported with St John’s wort. Extracts of the herb contain many active ingredients, with hypericin and hyperforin being best known. These compounds affect liver enzymes which affect several other pharmaceuticals. This phenomenon was first noted with immunosuppressant drugs, and then with oral contraceptives. Numerous cases were reported of women becoming pregnant while taking the pill along with St John’s wort. This led authorities in Sweden, the UK and Germany to warn women not to take the two medications at the same time. Other drugs which are affected include warfarin, digoxin, anti-depressants and some anaesthetics. Some reviews claim that almost half of all prescription drugs might be affected by St John’s wort. This remains one of the important reasons why people using St John’s wort should discuss this with their doctors and pharmacists.


More than 50 controlled studies show that St John’s wort is at least as effective as pharmaceutical anti-depressants. While it would therefore be reasonable to think that the herb could help those with IBS, the evidence to date does not support this. As with any medication, additional research helps to reveal which conditions St John’s wort can help and which it doesn’t. Unfortunately, irritable bowel syndrome does not appear to be among the conditions for which St John’s wort might be beneficial.