The various health effects of eating fish are well documented, but a new study reports on potential benefits specifically for people suffering from rheumatoid arthritis (RA).

The study, published this week in Arthritis Care & Research, found that eating fish at least twice per week correlated with lower RA disease activity and less swelling and tenderness in patients’ joints.

The cross-sectional analysis used baseline data from 176 participants in the Evaluation of Subclinical Cardiovascular Disease and Predictors of Events in RA (ESCAPE-RA) cohort study. The team used responses from dietary questionnaires to calculate each participant’s frequency of fish consumption.

Answers were categorized as “never to less than one serving per month,” “one serving per month to less than one serving per week,” “one serving per week,” and “two or more servings per week.”

Types of fish included tuna fish, salmon, sardines, trout, sole, halibut, poke and grouper, which were broiled, steamed, baked, or eaten raw.

Eating fish at least twice a week correlated with less joint swelling and tenderness than those who rarely or never ate fish. A blood marker showed that RA disease activity was also lower in frequent fish consumers.

Specifically, the team found that disease activity scores were an average of half a point lower in people who ate fish most often compared to those who ate the least.

While this may not seem like a significant difference, a score of less than 2.6 on the scale used in the study indicates remission, while a score of more than 5.1 refers to active disease, so a half-point difference is considered clinically significant in this case. The researchers explain the half-point difference equates to about one-third improvement reported in clinical trials for methotrexate drugs, which are considered standard of care for RA.

The researchers did adjust for demographic factors, as well as the use of any biologic disease-modifying RA drugs, fish oil supplements and smoking.

The team contributes the observed relationship between fish consumption and lower disease activity scores to the abundance of omega-3 fatty acids fish typically have. Omega-3s are known to have an anti-inflammatory element, and previous studies have suggested fish oil supplements can have similar results.

Fried fish, shellfish and meals that included fish within a mix of other ingredients (like a stir fry) were excluded because these types of meals tend to lack omega-3s.