A high dietary intake of lean and oily fish may slow the progression of disability in people with multiple sclerosis, a new study suggests. The anti-inflammatory and neuroprotective properties of the nutrients found in fish may be key, the authors said, adding that their findings underscore the potential importance of diet in managing the disease.

Emerging evidence indicates that diet may have a role in the development of inflammatory diseases, including MS, explain researchers from Karolinska Institute, in Stockholm, Sweden. 

While previously published research has linked fish consumption with lower levels of disability among those with MS, few studies have looked at whether it might slow or lessen the progression of disability. To explore this further, the research team drew on 2719 newly diagnosed participants in the Epidemiologic Investigation of Multiple Sclerosis study, a Swedish nationwide population based case-control study, all of whom were recruited between April 2005 and June 2015.

On entry to EIMS, all participants provided information on environmental exposures and lifestyle habits, including their consumption of lean and oily fish, which was categorised as: never or seldom; one to three times a month; and weekly, and scored from 2 to 6, depending on whether they ate lean or oily fish, or both. 

Their disease progression, measured using the Expanded Disability Status Scale, was tracked for up to 15 years through the Swedish MS Registry. Confirmed disability worsening was defined as an increase in the EDSS score of at least 1 point from baseline, sustained between two further check-ups, at least six months apart.

The highest fish consumption at diagnosis was linked to a 44 percent lower risk of confirmed disability worsening as well as a 45 percent lower risk of progressing to EDSS 3 and and a 43 percent lower risk of progressing to EDSS 4 compared with those who ate none or very little.

And the more lean and oily fish that was consumed, the lower was the risk of confirmed disability worsening and progression to EDSS 3 and 4, trends analysis indicated.

In 2021, 1719 participants completed an online follow-up questionnaire which assessed changes in fish intake over time. About 412 (24 percent) had altered their fish consumption: 288 had increased it; 124 had decreased it. Those who increased their score from 2–3 to a score of 5–6 within five years after diagnosis (133) had a 20 percent lower risk of confirmed disability worsening, compared with those who continued to eat little or no fish (400). Only 16 participants increased their fish consumption from a baseline score of 2 to a score of 5–6, but they had a 59 percent lower risk of confirmed disability worsening, compared with those who remained at the lowest level of consumption (101).

The findings held true even when potentially influential factors of physical activity, weight, smoking, alcohol intake, and sun exposure were accounted for. They also remained similar when further adjustment was made for vitamin D level.

This was an observational study, and as such, no firm conclusions can be drawn about cause and effect. And further research to validate the findings and investigate the underlying biological mechanisms is required, the researchers said. But they suggest that while omega-3 fatty acids, predominantly found in oily fish, may contribute to reduced disability progression, the beneficial effects observed from lean fish consumption suggest other factors may also play a significant role.

They also said the results underscore the potential role of diet, particularly fish consumption, as a modifiable factor that could complement existing therapeutic strategies for MS.

The study was published in the Journal of Neurology Neurosurgery and Psychiatry.