People who eat fish a few times each week are slightly less likely to suffer a stroke than those who only eat a little or none at all, according to an international analysis.
The omega-3 fatty acids in fish may lower stroke risk through their positive effects on blood pressure and cholesterol, wrote Susanna Larsson and Nicola Orsini of Sweden's Karolinska Institute in the journal Stroke.
Their analysis was based on 15 studies conducted in the United States, Europe, Japan and China, each of which asked people how frequently they ate fish, then followed them for between four and 30 years to see who suffered a stroke.
"I think overall, fish does provide a beneficial package of nutrients, in particular the omega-3s, that could explain this lower risk," said Dariush Mozaffarian, a Harvard School of Public Health epidemiologist whose research was included in the analysis.
"A lot of the evidence comes together suggesting that about two to three servings per week is enough to get the benefit."
Vitamin D, selenium, and certain types of proteins in fish may also have stroke-related benefits, he added.
Data for the analysis came from close to 400,000 people aged 30 to 103.
Over anywhere from a few years to a few decades, about 9,400 people had a stroke. Eating three extra servings of fish each week was linked to a six-per cent drop in stroke risk, which translates to one fewer stroke among a hundred people eating extra fish over a lifetime.
The people in each study who ate the most fish were 12 per cent less likely to have a stroke than those that ate the least.
Mozaffarian's report separated the effects of different kinds of fish and found that people who ate more fried fish and fish sandwiches, not surprisingly, didn't get any stroke benefit.
But the research can't prove that adding more non-fried fish to your diet will keep you from having a stroke, Mozaffarian told Reuters Health.
People "could have healthier diets in other ways, people could exercise more, people could have better education that could lead them to see their doctors more," he added, all of which could decrease their risk of strokes.
Still, most studies have tried to take those other health and nutrition factors into account to isolate the effects of fish as much as possible -- and they suggest a cause-and-effect relationship, he said.
It's likely that people who start out eating no fish or very little probably have the most to gain by putting it on their plate more often.
"You get a lot of bang for your buck when you go from low intake to moderate, a few servings per week," Mozaffarian said.
After that, the benefit from each extra serving probably goes down.
Fatty fish such as salmon and herring are especially high in omega-3s, The American Heart Association recommends at least two servings of fatty fish in particular each week.