Marine oil, often referring to fish oil rich in omega-3 polyunsaturated fatty acids (EPA and DHA), has been studied for its potential to reduce inflammation in autoimmune conditions such as rheumatoid arthritis (RA). Multiple randomized controlled trials and meta-analyses have demonstrated that supplementation with marine oil can lead to modest improvements in clinical outcomes for RA patients. These benefits include reduced joint pain, morning stiffness, and the need for nonsteroidal anti-inflammatory drugs (NSAIDs). The proposed mechanism involves the anti-inflammatory properties of EPA and DHA, which can alter the production of pro-inflammatory eicosanoids and cytokines.

Despite these positive findings, the overall magnitude of benefit is generally considered moderate, and marine oil is not a replacement for disease-modifying antirheumatic drugs (DMARDs). Guidelines from organizations such as the American College of Rheumatology note that fish oil supplementation may be considered as an adjunct therapy in RA, but emphasize that evidence is not strong enough to recommend it as a primary treatment. The quality and dosage of marine oil supplements can also impact outcomes, and not all studies have shown significant effects.

In summary, there is scientific validation for the use of marine oil as a supportive adjunctive therapy in RA, with evidence rated as moderate (3/5). It may provide symptom relief for some patients, particularly in reducing pain and inflammation, but it should not be relied upon as a sole therapy.