FISH oil supplements taken by millions for their health benefits do not reduce the risk of suffering a stroke, a new study suggests.
However, researchers said that eating oily fish at least twice a week may have a significant impact.
An analysis of studies involving almost 800,000 people in 15 countries found that there was no link between taking the capsules and a reduced risk of stroke.
Omega 3 fatty acid supplements and cod liver oil are taken by millions of people every day as it has been suggested they are good for the heart.
The capsules are thought to work by improving the health of blood vessels, lowering cholesterol and reducing inflammation. The market is worth at least £139m (€172m).
In the latest research, scientists examined 38 studies and found that consumption of fish was associated with a reduced risk of stroke.
People eating two to four servings a week were 6pc less likely to suffer a stroke. Those eating five or more portions of oily fish had a 12pc lower risk.
The researchers also looked at levels of omega 3 fatty acids in the blood and found that, comparing those with the highest levels and the lowest, there was no significant difference in stroke risk.
The findings suggest that the flesh of the fish must be eaten to gain the full benefits.
Fish is high in vitamins D and B, which have been linked to healthy blood vessels, while it also contains trace minerals such as iodine.
The scientists noted that if people eat large quantities of fish each week they tend to eat less red meat and other foods that are relatively unhealthy for blood vessels.
The researchers, writing in the 'British Medical Journal', also said that the apparent health benefits of oily fish over white fish may simply be down to the way it is cooked, as white-flesh fish tends to be fried.
Authors from the division of human nutrition at Wageningen University, in the Netherlands, suggested that although it is "reasonable" to advise that eating one or two portions of fish per week could reduce the risk of coronary heart disease and stroke, any benefit of omega 3 fatty acid supplementation is likely to be small. (©Daily Telegraph, London)