Can Eating Fish Lower The Risk of Strokes?

A recent analysis of 15 studies measuring the potential relationship between fish consumption and incidence of stroke in a combined total of 383,838 participants, found that eating fish at least three times per week was associated with a slightly lower risk of stroke.

The recent analysis, by Susanna C. Larsson, PhD and Nicola Orsini, PhD of the Division of Nutritional Epidemiology at the Karolinska Institutet in Stockholm, Sweden, was published online in the September 8, 2011 issue of Stroke, a medical journal of the American Heart Association.

As reported by Reuters Health for MedlinePlus, “Close to 800,000 people in the U.S. have a stroke each year, and 136,000 die from it. Smoking, drinking, being overweight and having high blood pressure and cholesterol are all linked to a higher risk of stroke.”

For purposes of their analysis, Dr. Susanna Larsson and Dr. Nicola Orsini of the Karolinska Institutet in Stockholm, Sweden, identified and reviewed fifteen published prospective studies that measured for a potential relationship between fish consumption and stroke risk. The 15 studies, which were located by searching the Embase and PubMed data bases through May 2011, included a combined total of 383,838 participants age 30 to 103. The studies were done in the U.S., Europe, Japan and China.

In each of the studies, the participants had been surveyed to determine how often they ate fish and related information, and then followed for a period of years, which varied between the studies from four years to 30 years, to determine incidence of strokes among the participants. Over the follow-up periods, the participants in the 15 studies suffered a combined total of 9,360 stroke events.

Drs. Larsson and Orsini indicated that they “conducted a dose–response meta-analysis to summarize the evidence from [these 15] prospective studies regarding the association between fish consumption and stroke risk.”

The authors’ meta-analysis of the 15 studies found that eating three extra servings of fish each week was associated with a 6% reduction in risk of stroke.

However, when the people in each study who ate the most fish were compared to those who ate the least, those who ate the most fish were 12 percent less likely to have a stroke than those who ate the least.

Drs. Larsson and Orsini concluded that, “These findings indicate that fish consumption is weakly inversely associated with the risk of stroke.”

“I think overall, fish does provide a beneficial package of nutrients, in particular the omega-3s, that could explain this lower risk,” Dr. Dariush Mozaffarian, a Harvard School of Public Health epidemiologist whose research was included in the analysis, told Reuters Health.

Drs. Larsson and Orsini wrote that omega-3 fatty acids in fish might lower stroke risk through their positive effects on cholesterol and blood pressure.

Dr. Mozaffarian’s research separated the effects of eating different kinds of fish, and found that eating more fried fish or fish sandwiches did not lower one’s risk of stroke.

But the research did not prove that eating more non-fried fish would prevent you from having a stroke. People who eat a lot of fish, Mozaffarian told Reuters Health, “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.” All of those things might decrease their risk of stroke, he postulated.

Dr. Mozaffarian also said that people who start out eating no fish or very little probably have the most to gain by increasing their fish consumption. “You get a lot of bang for your buck when you go from low intake to moderate, a few servings per week,” he said. After that, the benefit from each extra serving probably decreases.

Fatty fish such as salmon and herring are especially high in omega-3s, and the American Heart Association recommends eating at least two servings of fatty fish each week.

The full report of the meta-analysis by Dr. Susanna C. Larsson and Dr. Nicola Orsini of the Karolinska Institutet in Stockholm, Sweden is available online in the September 8, 2011 issue of Stroke, a medical journal of the American Heart Association.