Eating Fish Eases Rheumatoid Arthritis

August 9, 2017

Lower disease activity may be associated with higher intake of fish as a whole food.

Several past trials have tested the effect of fish oil supplementation for patients who are living with rheumatoid arthritis. Now a new study suggests that lower disease activity may be associated with higher intake of fish as a whole food.

Researchers found a statistically and clinically significant reduction in Disease Activity Score 28 using C‐reactive protein (DAS28-CRP) among participants with rheumatoid arthritis who consumed fish more than twice a week, compared with those who consumed fish less than once a month or never.

“Our observed difference in DAS28-CRP of 0.49 between the highest and lowest categories of fish consumption is approximately one-third the magnitude of previously reported pre- and post-treatment differences in DAS28 among methotrexate users,” said the study authors, led by Sara K. Tedeschi, MD, MPH, of Brigham and Women’s Hospital and Harvard Medical School.

They reported their findings in a recent issue of Arthritis Care and Research.

The study

This novel investigation of the relationship between consuming fish as a whole food and rheumatoid arthritis disease activity was conducted as a cross-sectional analysis using baseline data from participants in the Evaluation of Subclinical Cardiovascular Disease and Predictors of Events in Rheumatoid Arthritis (ESCAPE-RA) cohort study. The ESCAPE-RA study enrolled adults aged 45 to 84 years who met the American College of Rheumatology 1987 rheumatoid arthritis classification criteria.

Participants completed a 120-item food frequency questionnaire, which assessed diet over the past year. For each item, frequency of consumption was recorded on a 9-point scale, ranging from “never to less than once a month” to “twice a week or more.” Participants also indicated small, medium, or large servings for each item, which allowed total average energy per day to be calculated.

For the current study, frequency of fish consumption was calculated using 2 items: “tuna fish, salmon, sardines (cooked or raw including sashimi or sushi)” and “other broiled, steamed, baked or raw fish (trout, sole, halibut, poke, grouper, etc.).” These categories were selected because of their higher omega-3 fatty acid content compared with other seafood items on the questionnaire. Fried fish, non-fried shellfish, and fish in mixed dishes were not included for the purposes of this study.

Of 176 participants, 35 (19.9%) reported infrequent fish consumption (never to less than once a month); 31 (17.6%) were frequent consumers (twice a week or more).

The findings

Linear regression models tested the relationship between frequency of fish consumption and DAS28-CRP. All models were adjusted for total average energy consumed per day. After adjusting for age and sex, DAS28-CRP was significantly lower, by an average of 0.65, among participants consuming fish twice a week or more compared with those eating fish less than once a month or never.

With additional adjustment for confounders, such as race, body mass index (BMI), smoking, education, and annual income, DAS28-CRP was significantly lower, by an average of 0.49, in participants consuming fish twice a week or more compared with those who consumed fish less than once a month or never.

Sensitivity analyses, which adjusted for the use of biological disease-modifying antirheumatic drugs and fish oil supplements, obtained similar results.

Implications

Although it’s beyond the scope of the current analysis, there has been speculation that lower rates of rheumatoid arthritis in some countries may be related to cultural or environmental differences, including frequency of fish consumption.

“Our observation that baseline consumption of fish ≥2 times per week was associated with lower DAS28-CRP at the same point in time may either reflect a generally healthier lifestyle among those who eat fish most often or may reflect an effect of consuming fish as a whole food that contains various macronutrients and micronutrients in addition to omega-3 fatty acids,” the authors wrote.

The group that consumed fish more than twice a week had some baseline traits that generally can be associated with improved disease activity, such as lower BMI and higher socioeconomic status. Still, the prevalence of smoking was highest in this group, making it difficult to draw conclusions about how potential confounders could affect the relationship between fish consumption and DAS28-CRP.

The ESCAPE-RA cohort was predominantly composed of white, well-educated, married patients who had longstanding rheumatoid arthritis, meaning the results may not generalize to other populations. Because the study is cross-sectional, firm conclusions cannot be drawn about the impact of frequent fish consumption on rheumatoid arthritis disease activity. A randomized controlled trial would be required to provide firm evidence that greater fish consumption lowers rheumatoid arthritis disease activity.

References:

Tedeschi SK, Bathon JM, Giles JT, et al. “The relationship between fish consumption and disease activity in rheumatoid arthritis.” Arthritis Care Res (Hoboken). 2017 Jun 21. doi: 10.1002/acr.23295. [Epub ahead of print]