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Fish Can Contribute to Increased Stroke Risk

Americans living in the southern “stroke belt” states consume more fried fish, which may contribute to the region’s high stroke mortality rate….

Fadi B. Nahab, MD, medical director of the Stroke Program at Emory University Hospital in Atlanta, Georgia explains that, “Eating less healthy fish may be contributing to America’s stroke belt and to racial disparities in stroke…. Our study is the first major study to look at geographic differences in fish consumption in and out of the stroke belt.”  

People who live in the states of North Carolina, South Carolina, Georgia, Alabama, Mississippi, Tennessee, Arkansas, and Louisiana are more likely to die from stroke than people living in other parts of the U.S., the researchers note.

Omega-3 fatty acids in fish, especially oily fish, favorably alter platelet aggregation, blood pressure, lipid profile, and endothelial function and may reduce the risk for ischemic stroke. However, when fish is fried, it loses natural omega-3 fatty acids. Moreover, in the U.S., most fish served fried tends to be from lean species that pack lower amounts of omega-3 fatty acids.

The Reasons for Geographic and Racial Differences in Stroke (REGARDS) study is a national, population-based longitudinal cohort study with oversampling of blacks and persons living in the stroke belt. The total cohort is made up of 30,239 participants aged 45 years and older.

Dr. Nahab’s team studied 21,675 of the participants; 34% were black, 56% were women, and 74% were overweight (body mass index, 25.0 kg/m2 or higher). Their mean age was 64.9 years.

Forty-four percent lived in non–stroke belt states, 34% lived in the stroke belt, and 19% lived in the stroke “buckle” — the coastal plain region of North and South Carolina and Georgia — an area within the stroke belt with the highest stroke mortality rates.

Although black participants consumed more total fish servings per week than their white counterparts, most of the additional consumption was in the form of fried fish. “African Americans were 3.5 times more likely to have 2 or more servings of fried fish per week than whites, regardless of where they lived,” Dr. Nahab said. “Overall, African Americans ate twice as much fried fish as whites did in the study.”

Total average servings of fish per week were lower among residents of the stroke belt and stroke buckle than residents of other areas, but stroke belt and stroke buckle residents ate less nonfried fish and more fried fish.

The American Heart Association (AHA) recommends 2 or more servings of fish (preferably oily fish) per week for people without known cardiovascular disease. In people with documented cardiovascular disease, the AHA suggests considering additional supplements of eicosapentaenoic acid and docosahexaenoic acid.

In the REGARDS study, less than one quarter of the participants (5022/21,675) ate 2 or more servings of nonfried fish per week.

Compared with people outside the stroke belt, those in the stroke belt were 17% less likely to eat 2 or more weekly servings of nonfried fish (odds ratio [OR], 0.83; 95% confidence interval [CI], 0.77 – 0.90) but 32% more likely to have 2 or more weekly servings of fried fish (OR, 1.32; 95% CI, 1.17 – 1.50).

People living in the stroke buckle were 11% less likely to get at least 2 weekly servings of nonfried fish (OR, 0.89; 95% CI, 0.81 – 0.98), but they were 17% more likely to have 2 or more weekly servings of fried fish (OR, 1.17; 95% CI, 1.00 – 1.50) than those living outside the stroke belt.

It is possible, he added, that differences in dietary fish consumption — and specifically cooking methods such as frying — contribute to the higher rates of stroke among those who live in the stroke belt and among blacks.

Dr. Nahab concludes that, “Because the fish served fried frequently has lower levels of the omega-3 fats docosahexaenoic acid and eicosapentaenoic acid, which have been shown to be beneficial for cardiovascular disease prevention, increases in oily fish consumption (salmon, herring, mackerel), limiting fried fish intake, and/or supplementation of fish oil may potentially contribute to stroke prevention.”

In the current study, only 6% of participants reported taking fish oil supplements, including 5% of white participants and 1% of black participants.

Neurology, Dec. 22, 2010