There is emerging and promising evidence showing a link between eating more oily fish could help protect against multiple sclerosis.

Eating oily fish like salmon and tuna regularly every week is said to help protect against cardiovascular disease, arthritis and even dementia.

Emerging and "exciting" new evidence now suggests the rich source of omega-3 fatty acids could be a weapon against multiple sclerosis, which is on the rise in Australia.

Preliminary results of US study of more than 1000 Americans, recently presented at the 2018 American Academy of Neurology's annual Meeting, found people who were consuming fish at least once a week, or were consuming fish oil supplements, were nearly 50 per cent less likely to get MS.

Very similar results have been found in Australia, says Dr Lucinda Black, from the School of Public Health at Curtin University.

Researchers, led by Dr Black, examined the diets of more than 650 Australians and found the regular fish eaters were significantly less likely to experience an initial demyelinating event - a precursor to MS.

"What I found is that there was a 50 per cent reduced risk of MS with people consuming two serves a week of oily fish," said Dr Black.

The yet to be published research suggests that eating oily fish could be particularly beneficial for those at high risk of getting MS, said Dr Black.

"If you have a family history of MS, that's when it would be important," said Dr Black.

Other risk factors include smoking, a history of glandular fever and low vitamin D.

Multiple sclerosis is a disease of the central nervous system that affects communication between the brain and other parts of the body.

It causes the body's immune system to attack the myelin, the fatty white substance that insulates and protects the nerves.

Symptoms of MS may include fatigue, numbness, tingling or difficulty walking.

The evidence is "certainly" already there to explain why omega-3 benefits brain health.

Dr Black says this could be the same reason why it appears to provide a protective effect against MS.

"Because multiple sclerosis involves the myelin sheath around the nerves and that is largely made up of omega-3 fatty acids, so it has both structural and functional importance in the brain," explained Dr Black.

New data from the Menzies Institute for Medical Research shows 25,600 Australians now live with the neurological disorder, a rise of 4400 in eight years.

Dr Matthew Miles, MS Research Australia CEO, says genetics alone can't be responsible for the rise in prevalence.

"There has to be other environmental reasons and we also know that it can't be just because we're getting better at diagnosing it," Dr Miles said.

He said the role of diet and lifestyle in the prevention and treatment of MS is another "exciting" area of research that has emerged.

"It's alway harder to prove but this is a very important and encouraging and developing part of MS," he said.