New Zealand Green Lipped Mussel Oil (GLMO) has been investigated for its potential role in supporting or treating rheumatoid arthritis (RA) due to its anti-inflammatory properties. The oil contains a unique combination of omega-3 fatty acids, especially eicosatetraenoic acid (ETA), along with other bioactive lipids not typically found in fish oils. These compounds are believed to modulate inflammatory pathways relevant to RA.

Several small clinical studies and animal experiments suggest that extracts of the green-lipped mussel may reduce joint pain and morning stiffness in people with RA, possibly by inhibiting leukotriene and prostaglandin synthesis. Some randomized controlled trials have reported mild improvements in symptoms compared to placebo; however, the evidence is mixed, with other studies showing no significant effect. Notably, most clinical trials have involved mussel extracts in powder or freeze-dried form, and there are fewer robust studies specifically on the oil extract.

Major reviews and meta-analyses conclude that while there is some scientific basis for the anti-inflammatory effects of GLMO, the quality and consistency of evidence for its efficacy in RA are limited. Most guidelines do not recommend it as a standard treatment, citing insufficient evidence. In summary, while there is some scientific interest and weak evidence supporting its use, larger and better-designed clinical trials are needed to confirm benefits for rheumatoid arthritis.