Researchers say certain fish diets seem to help in the prevention of MS, but scientists aren’t sure yet why.

Eating fish may reduce the risk of developing multiple sclerosis.

A preliminary study published this week concluded that eating fish and consuming over-the-counter fish oil supplements is associated with a 45 percent reduced risk of developing multiple sclerosis (MS).

Fish consumption also showed success against clinically isolated syndrome (CIS), in which a person will have one MS-type attack but no further disease development.

The full study will be presented at the American Academy of Neurology’s 70th annual meeting in Los Angeles in late April.

Fish provide a much-needed polyunsaturated fatty acid (PUFA) known as omega-3, which have been shown to be neuroprotective in nature. They’ve also shown ability to suppress MS-related inflammation in nonhuman research.

In the latest study, a group of experts in Southern California wanted to see if a simple lifestyle modification such as eating fish could reduce the risk of MS.

“We are increasingly recognizing that MS is not only a chronic inflammatory disease of the central nervous system but also often leads to diffuse neuro-degeneration.” said Dr. Annette Langer-Gould, who is associated with Kaiser Permanente Southern California in Pasadena, a member of the American Academy of Neurology, and a study author.

“While the cause is not known, the rising prevalence of MS has led to increased interest in identifying modifiable risk factors including diet.”

Modifiable risk factors (MFRs) are choices people with MS can make that may offer benefit or detriment to their illness.

Smoking tobacco and consuming alcohol are two MRFs to be avoided for those with MS.

Taking vitamin D and vitamin B-12 have been proven beneficial for people with MS and are considered MRFs worth adopting.

The new research analyzed the diets of 1,153 people in the MS Sunshine Study out of Kaiser Permanente Southern California.

Fish consumption was categorized.

Participants were divided into two groups.

Those considered to have a high fish intake either ate fish once a week or took a fish oil supplement along with eating fish one to three times per month. Any over-the-counter fish oil supplements were considered OK.

Low fish intake was defined as less than one serving of fish per month and no fish oil supplements.

“Most fish consumed in California is salmon or [Pacific] tuna, which are not as high in mercury as swordfish and mackerel, also known for their high omega-3 content,” explained Langer-Gould.

Some tuna does have higher mercury content. Shrimp was another omega-3 seafood consumed during the study.

Langer-Gould described how “fish or other seafood consumption is particularly interesting because it’s the main determinant of circulating and tissue levels of omega-3 polyunsaturated fatty acids (omega-3 PUFAs).”

Because omega-3 PUFAs are neuroprotective and have anti-inflammatory effects, it “provides at least two biologically plausible mechanisms whereby higher omega-3 PUFA intake and biosynthesis could protect against development of MS,” Langer-Gould told Healthline.

Whether higher fish or omega-3 consumption reduces the risk of MS is unclear.

What is also not clear is why fish consumption is protective.

The study looked at genetic variations as a way to measure whether omega-3 fatty acids might be the key to why fish and seafood consumption is protective versus eating other foods, such as red meat and processed items.

Researchers found 2 of the 13 genetic variations examined were associated with lower MS risk, even after accounting for the higher fish intake. This may mean that some people have a genetic advantage to regulating fatty acids. But “it does not mean that people with a certain genotype need to eat more fish than others to get the same health benefits,” Langer-Gould clarified.

The next step is for research to try to replicate the findings in another dataset.

“If our findings are confirmed, it will be important to determine whether the protective effect is mediated by the anti-inflammatory, metabolic, and/or neuroprotective actions of omega-3 fatty acids and whether fish/fish oil consumption could improve MS prognosis,” said Langer-Gould.

“While the study did not look at the effect of fish/fish oil consumption on MS prognosis, the findings could certainly lead to lifestyle modification interventions that could improve overall health for MS patients and perhaps prevent MS in their offspring,” Langer-Gould explained.

MS isn’t considered genetic but may be seen in familial situations.

Langer-Gould emphasized that this study “simply shows an association and not a cause and effect.”

More research is needed.

Editor’s note: Caroline Craven is a patient expert living with MS. Her award-winning blog is, and she can be found on Twitter.