However, taking fish oil supplements doesn't seem to have the same effect.
A team of international researchers analysed the results of 38 studies to help clarify the association between fish consumption and risk of stroke or mini-stroke (transient ischaemic attack or TIA). Collectively, these conditions are known as cerebrovascular disease.
Regular consumption of fish and long chain omega 3 fatty acids has been linked with a reduced risk of coronary heart disease and current guidelines recommend eating at least two portions of fish a week, preferably oily fish like mackerel and sardines.
However, evidence supporting a similar benefit for stroke remains unclear.
Researchers led by Dr Rajiv Chowdhury - a native of Bangladesh - at Cambridge University and Professor Oscar H Franco at Erasmus MC Rotterdam looked at 38 studies involving nearly 800,000 individuals in 15 countries and including patients with established cardiovascular disease (secondary prevention studies) as well as lower risk people without the disease (primary prevention studies).
Fish and long chain omega 3 fatty acid consumption was assessed using dietary questionnaires, identifying markers of omega 3 fats in the blood, and recording use of fish oil supplements.
A total of 34,817 cerebrovascular events were recorded during the studies.
After adjusting for several risk factors, participants eating two to four servings a week had a moderate but significant 6 per cent lower risk of cerebrovascular disease compared with those eating one or fewer servings of fish a week, while participants eating five or more servings a week had a 12 per cent lower risk.
An increment of two servings per week of any fish was associated with a 4 per cent reduced risk of cerebrovascular disease.
In contrast, levels of omega 3 fats in the blood and fish oil supplements were not significantly associated with a reduced risk, researchers said in a statement.
Several reasons could explain the beneficial impact of eating fish on vascular health, said the researchers. For example, it may be due to interactions between a wide range of nutrients, like vitamins and essential amino acids, commonly found in fish.
Alternatively, eating more fish may lead to a reduction in other foods, like red meat, that are detrimental to vascular health.
The study was published in British Medical Journal.
