A new Canadian study has found that simple "probiotic" bacteria are effective in treating ulcerative colitis, a painful disease caused by an immune system attack on the body's intestinal tissue and colon.

Researchers at the University of Alberta found six weeks of treatment with pills containing so-called "good" bacteria, or probiotics, can turn the inflamed and bleeding colons of many patients with ulcerative colitis into virtually normal tissue.

Probiotics are not new but their healing powers are just starting to be investigated by the medical community. They are the easily obtained bacteria that turn milk into yogurt and are thought to restore intestinal bacteria balance.

Patients with colitis often have an overgrowth of "bad" bacteria and not enough of the "good" ones. They experience abdominal pain and bloody diarrhea from inflammation and ulcers in the large bowel. The cause of the illness is unknown though genetic susceptibility is thought to play a role.

Researchers tested whether heavy doses of probiotics could help combat the overgrowth of "bad" bacteria in colitis sufferers and help them to heal.

They tested 34 patients with mild to moderate active ulcerative colitis who were not responding to conventional therapy. The patients were treated with VSL, a probiotic mixture containing 450 billion live probiotic bacteria made up of eight lactic acid bacterial species.

Colitis sufferer Joanne Kosowan was diagnosed with the disease 22 years ago. "I was in considerable pain with a lot of bloating, severe cramping and bleeding," she told CTV News. "Yet within a week of being on the probiotics as part of the University of Alberta test I felt better."

The study found that the medication brought about a demonstrated remission in 53 per cent of the study group (18 patients), and a favourable response in another 24 per cent (8 patients). There was no response in 9 per cent of patients and a worsening of symptoms in 9 per cent. Two patients did not complete the final assessment.

About 30,000 Canadians have ulcerative colitis. Unlike the steroid treatment that many of them endure, the probiotic treatment caused virtually no side effects, other than mild bloating.

"This is a potentially new way of treating inflammatory bowel disease... that is probably quite safe and doesn't have a lot of side effects," says Dr. Hillary Steinhart of Toronto's Mount Sinai Hospital.

Doctors don't know why the probiotic treatment doesn't work on all patients or if its effects are permanent. They also say patients shouldn't self medicate or replace current treatments with probiotics off the store shelf.

There is no proof that the doses available in commercial products help symptoms. But they say the study's results are encouraging and probiotics could next be tested on patients with Crohn's disease.

The results of the study are published in the latest edition of the American Journal of Gastroenterology.