New Zealand green-lipped mussel (Perna canaliculus) has been studied as a complementary therapy for rheumatoid arthritis (RA) due to its anti-inflammatory properties. The scientific interest originated in the 1970s when lower rates of arthritis were observed in coastal Maori populations, which was hypothesized to be linked to their diet rich in shellfish, including green-lipped mussels. Since then, several small randomized controlled trials and open-label studies have been conducted. The active components are believed to include omega-3 polyunsaturated fatty acids and other bioactive lipids, which may help modulate inflammation.

However, the clinical evidence is limited and mixed. Some studies suggest modest benefits in reducing joint pain and morning stiffness in RA patients, but the effect sizes are generally small and not consistently statistically significant. Meta-analyses and systematic reviews often conclude that while green-lipped mussel extract appears to be well tolerated, the overall quality of evidence is low, with methodological flaws, small sample sizes, and short study durations. The ingredient is more commonly studied for osteoarthritis than RA, and regulatory bodies do not endorse it as a first-line or proven therapy for rheumatoid arthritis.

In summary, there is some scientific rationale and limited clinical evidence supporting the use of New Zealand green-lipped mussel for RA, but the strength of evidence is weak (rated 2/5), and it should not replace standard medical treatments.