Because there is no effective cure for the autoimmune disease, many patients have turned to supplements that are known to affect the immune system and inflammation -- and therefore could theoretically slow the progression of disease in the brain.

But so far, evidence that a supplement-boosted diet can help people with MS has been lacking. And the new data add to that skepticism, the report's lead author said.

"We think this study proves that omega-3 has no beneficial effect on MS disease activity," Dr. Oivind Torkildsen from Haukeland University Hospital in Bergen, Norway, told Reuters Health.

Based on the findings, he added, "We have stopped advising patients to take omega-3 supplements."

About 400,000 people in the United States have MS, in which the protective coating around nerve fibers starts breaking down, slowing the speed of signals traveling between the brain and body.

Common symptoms are problems with balance and muscle coordination. Some patients have memory loss and trouble with logical thinking.

Studies have suggested that as many as one-third of people with MS have tried fish oil supplements, despite a lack of hard evidence supporting their use.

So the researchers set up a small but rigorous trial, in which 92 people with the disease were randomly assigned to take fish oil supplements or fish oil-free placebo pills daily.

The fish oil supplements contained the omega-3 fatty acids EPA and DHA.

Study participants took only their assigned pills for six months, then continued on the supplements while also getting treated with the injectable MS drug interferon beta 1-a for another year and a half.

Torkildsen and his colleagues found that after both rounds of treatment, patients assigned to take fish oil weren't any better off than those on the placebo.

By two years from the start of the study, just under half of patients in both groups had had a disease relapse, with new or worsening neurological symptoms.

Based on changes in brain scans taken regularly during the study, MS progressed in 13 patients taking fish oil and 12 on the placebo pills over those two years.

There was also no difference in fatigue or quality of life reported by patients taking either type of supplement, the researchers reported Monday in Archives of Neurology.

The supplements used in the study, marketed as Triomar, were provided by Pronova Biocare. Merck added some of the additional funding, and study researchers individually reported financial ties to Merck and other pharmaceutical companies.

The findings don't mean that no one with MS should be taking omega-3 supplements, according to Dr. Bianca Weinstock-Guttman, an MS researcher from the University at Buffalo.

It's likely, she said, that the supplements combined with diet changes -- such as eating less saturated fat, and lowering total cholesterol -- may play a role in slowing the course of the disease along with medications.

"The adding on of (fatty acids) may not make a difference if the rest of the diet doesn't change," Weinstock-Guttman, who wasn't involved in the new study, told Reuters Health.

"I would focus on a good healthy, balanced diet," agreed Dr. Sharon Lynch, who studies MS treatment at the University of Kansas Medical Center in Kansas City but also wasn't tied to the new research.

"I think we're better off trying to eat better than taking a bunch of supplements to make up for the fact that we're not eating better," she said.

Regular aerobic exercise can also lessen fatigue in people with MS, Lynch told Reuters Health -- but fish oil supplements seem to be off the list of potentially-helpful interventions.

The supplements can be bought over-the-counter for about 50 cents per day for the doses used here.

"The omega-3s will not hurt you, because they seem to be good for cholesterol and the heart," Lynch said, "but they're not likely to do much for the MS itself."

SOURCE: bit.ly/J5MLHx Archives of Neurology, online April 16, 2012.

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