Fish oil

What fish oil might do, and what it might not

Fish oil may modestly reduce pain for some people with RA.

That doesn't mean it is controlling the inflammation that can damage joints.

Fish oil should not replace disease-modifying treatment.

What the evidence shows

When researchers pooled trials of marine oils in people with RA, they found a small average reduction in pain. The evidence for that pain effect was rated moderate in quality. Importantly, that rating describes how confident we are in the finding, not how large the benefit is.

The evidence does not establish fish oil as a treatment that controls the underlying RA.

Moderate-quality evidence, small effect

The evidence can be reasonably convincing while the benefit itself is still modest.

Evidence quality tells us how confident we are in the estimate. It doesn't tell us the effect is large.

What about algae oil?

People who don't eat fish often look for algae oil. That can supply EPA and DHA without fish.

The pain evidence on this page comes from marine-origin oils, mostly fish oil. That pooled review did not include algal-oil trials. It also left out plant oils such as flaxseed, because the body converts only small amounts of those into EPA and DHA.

Algae oil is not automatically the same as the marine oils that were studied. One later small trial used microalgae DHA in enriched foods, including items that were not plant-based. That is not enough to treat algae-oil capsules as having the same small pain evidence.

For questions about overall eating patterns rather than fish-oil supplements, see diet and nutrition.

What taking part usually involves

• Taking capsules regularly. Products differ, including in EPA and DHA content.
• A commercial bottle may not match the oils used in the trials.
• Deciding whether a small possible benefit is worth the cost and effort.