EPA and DHA, the long-chain omega-3 fatty acids found in oily fish and fish oil supplements, have a well-established role in reducing systemic inflammation and a specific mechanistic effect on joint health. The evidence is sufficient to support their regular use in adults with inflammatory joint conditions and in those seeking to reduce the inflammatory component of musculoskeletal pain.
The Mechanism
Arachidonic acid, an omega-6 fatty acid that predominates in the modern Western diet, is the substrate from which pro-inflammatory eicosanoids including prostaglandin E2, leukotriene B4, and thromboxane A2 are synthesised. EPA competes directly with arachidonic acid for the same enzymatic pathways, producing eicosanoids with substantially lower inflammatory potency. DHA is converted in the body to resolvins and protectins, compounds that actively resolve inflammation rather than simply blocking it.
The Evidence in Arthritis
Multiple meta-analyses of randomised controlled trials in rheumatoid arthritis have demonstrated that fish oil supplementation reduces morning stiffness, tender joint count, and NSAID requirements. The effect is dose-dependent, with higher doses of 3 to 4 grams of EPA and DHA daily producing larger effects. In osteoarthritis, the evidence is more modest but consistently points toward reduced pain and improved function with regular fish oil use.
The Practical Recommendation
- Consume oily fish such as salmon, mackerel, sardines, or herring at least three times per week
- If supplementing, target at least 2 grams of combined EPA and DHA daily, noting that the fish oil capsule total weight does not equal EPA and DHA content
- Choose a product with third-party testing for heavy metal contamination and oxidation
- Allow four to six weeks for meaningful clinical effects, as omega-3 incorporation into cell membranes takes time