The first trial in increasing dietary fiber in a primary care setting is published on today. It reports that soluble fiber (psyllium) is an effective treatment for irritable bowel syndrome (IBS). On the other hand, insoluble fiber such as bran may worsen symptoms.

Irritable bowel syndrome is characterized by abdominal pain and an irregular bowel habit. It affects about 10 percent of the population. To help alleviate symptoms, the increase in dietary fiber is recommended. However, there is incomplete confirmation that fiber truly alleviates symptoms. In fact, some studies have suggested that insoluble fiber may even aggravate symptoms.

In order to eliminate this uncertainty, Dr René Bijkerk from University Medical Center Utrecht and colleagues studied 275 patients aged 18 to 65 years. They all had irritable bowel syndrome. They received at random either 10 grams of psyllium (soluble fiber), bran (insoluble fiber), or placebo (rice flour) twice a day for twelve weeks.

After one, two and three months, patients were assessed. They used standard scoring scales to evaluate symptom relief, severity of abdominal pain and quality of life.

Results indicated that psyllium was the most efficient treatment for irritable bowel syndrome. There were a considerably superior number of patients reporting satisfactory symptom relief. Symptom severity was reduced by 90 points in the psyllium group, 49 points in the placebo group, and 58 points in the bran group, after three months of treatment. But there was no report of differences between the groups in abdominal pain or quality of life.

An interesting fact was that bran showed no clinically relevant advantage. In addition, many patients seemed to be intolerant to bran and as a result the dropout rate was highest in this group.

The authors remark that these results support the recommended addition of soluble fiber such as psyllium. However, bran does not appear as an effective first treatment approach in the clinical management of irritable bowel syndrome. In fact, they conclude that bran may worsen symptoms of irritable bowel syndrome and should be advised only with caution.

“Soluble or insoluble fibre in irritable bowel syndrome in primary care? Randomised placebo controlled trial”
C J Bijkerk, general practitioner, N J de Wit, associate professor of general practice, J W M Muris, associate professor of general practice, P J Whorwell, professor of medicine and gastroenterology, J A Knottnerus, professor of general practice, A W Hoes, professor of clinical epidemiology and general practice
BMJ 2009; 339:b3154

Written by Stephanie Brunner (B.A.)