Taking omega-3 fish oil supplements is often touted as a way simple way to protect your heart - but experts say the evidence that it does any good is flimsy at best.
UK-based Cochrane researchers looked at trials in over 100,000 people and found little proof that it prevented heart disease.
They say the chance of getting any meaningful benefit from taking omega-3 is one in 1,000, the BBC reports.
Eating oily fish, however, can still be recommended as part of a healthy diet.
The review mainly looked at supplements rather than omega-3 from eating fish. Experts still believe the latter is good for the heart as well as general health.
The NHS says people should try to eat two portions of fish per week, one of which should be oily fish, such as salmon, fresh tuna or mackerel, to get enough "good" fats.