Short answerNobody can say yet. The one large trial compared two doses of fish oil, and a higher dose did no better than a low one.
Evidence grade
Does not helpNot enough evidenceHelps a littleGood evidence
Not enough evidence yet
What it is
Fish oil is rich in omega 3 fatty acids, which are thought to calm inflammation. It is sold as capsules and liquids. The idea is that a higher intake of omega 3 might ease pain and slow wear in a knee with arthritis.
What the research shows
gave 202 people with knee arthritis and regular knee pain either high dose fish oil or a low dose blend for two years. Neither the patients nor the researchers knew which they had. Both groups improved. The high dose group did no better than the low dose group, and cartilage on MRI did not differ. If anything, the low dose group had less pain at two years, which the authors said needs further study.
Reviews of the wider research agree that the evidence is weak. found no clear benefit in osteoarthritis, and found no lasting effect from any of them. The Australian trial did not include a group on a plain placebo, so it cannot show whether fish oil beats no treatment. The low dose product also contained another oil that may have had its own effect.
Risks and effort
Fish oil can cause a fishy aftertaste, burping and an upset stomach. At high doses it may thin the blood a little, so tell your doctor or pharmacist before you start if you take a blood thinner or have an operation planned.
