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Fried Fish Seen to Raise Stroke Risk
1/6/2011
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by Craig Weatherby


Most evidence suggests that stroke-prevention ranks among the main benefits of eating fish and fish oil.
 
We’ve reported on the epidemiological evidence linking higher fish intake to lower stroke risk… see “Stroke: An Update on Fish and other Factors” and “Fish May Reduce Rates of “Silent” Stroke”.
 
And a recent animal study indicates that DHA – one of the two key omega-3s in fish fat – may even reduce the brain damage resulting from a stroke (see “Omega-3 DHA Helped Rats Avoid Stroke Harm”.)

Why would fried fish raise stroke risk?
Fish contain omega-3 fatty acids (EPA and DHA), which is why fish is heart-healthy, and why the American Heart Association recommends at least two meals of fatty fish (e.g., salmon, sardines, tuna, mackerel) per week.
 
But breading and then deep-frying fish in vegetable oil destroys many of its omega-3s and overwhelms them with the omega-6 fatty acids in the oil … some or all of which will have been damaged (e.g., oxidized) by exposure to the high heat of frying.
 
Omega-6s fats are essential and are certainly heart-healthy in moderation, but the average American’s diet is grossly overloaded with omega-6-rich vegetable oils, providing about 25 omega-6 molecules for every omega-3 molecule consumed.
 
This ratio stands in stark contrast to the diets human adapted to over eons of evolution, which provided omega-3s and omega-6s in much closer balance (i.e., an estimated one part omega-3s to three parts omega-6s).
 
And numerous cell and animal studies show that omega-6 fatty acids tend to promote inflammation… a key driver of cardiovascular disease, cancer, and other ills (see the “Omega-3 / Omega-6 Balance” section of our News Archive).
 
In 2009, the American Heart Association (AHA) issued a study commissioned to look into claims that diets excessively high in omega-6 fats may promote cardiovascular disease.
 
Their panel reviewed the existing evidence, and said they found no signs that omega-6s could be harmful, as long as people also consume the minimum recommended amounts of fish or fish oil (see “Heart Association Appears Blind to Risks of America’s “Omega-Imbalance”).
 
However, scientists from NIH took a hard look at the AHA review, and in a paper published late last year, they refuted its main conclusion very convincingly. (See “Heart Group's Omega-6 Advice Takes a Huge Hit”.)
 
In fact, the NIH group’s analysis confirmed growing, evidence-based fears that the average American diet, grossly overloaded with omega-6 fats, does in fact promote cardiovascular disease.
But most of the epidemiological studies detect a very critical distinction between deep-fried fish – which seems to increase stroke risk – and fish served in other forms (raw, baked, roasted, broiled, grilled, poached, sautéed).
 
As Harvard researchers wrote in 2005 when they reported their findings from a study among 4,775 older adults, “… consumption of tuna or other broiled or baked fish is associated with lower risk of ischemic stroke, while intake of fried fish or fish sandwiches is associated with higher risk” (Mozaffarian D et al. 2005).
 
Now, research by scientists at Atlanta’s Emory University adds even more evidence that diets featuring fried fish pose a stroke risk.
 
People in the “stroke belt” suffer the nation’s highest rates
The study involved people living in the “stroke belt”, which covers Alabama, Arkansas, Georgia, Louisiana, Mississippi, North Carolina, South Carolina and Tennessee.
 
In these states, the risk of dying from stroke is higher than in other parts of the country. For example, in Alabama the annual death rate from stroke is 125 fatalities per every 100,000 people, versus a national average of 98 stroke deaths per 100,000 people.
 
Stroke mortality rates are highest in the stroke belt’s so-called “stroke buckle” …the coastal plain region of North Carolina, South Carolina and Georgia.
 
And among all people in the stroke belt, African-Americans suffer the highest stroke rates of all.
 
The Emory University team analyzed data collected in the long-running REGARDS (Reasons for Geographic and Racial Differences in Stroke) trial conducted by the University of Alabama.
 
The REGARDS study recruited 21,675 people over the age of 45, starting in 2003, and continues to follow them to record their diet/lifestyle habits and health status.
 
Participants were interviewed by phone and received an in-home physical examination. They answered questions about how often they ate oysters, shellfish, tuna, fried fish and other fish not fried.
 
Twenty-one percent of the REGARD study participants were from the “stroke buckle”, 34 percent were from the rest of the stroke belt and 44 percent were from the other 40 contiguous states.
 
Fewer than one in four study participants consumed the two or more servings of non-fried fish per week recommended by the American Heart Association (AHA).
 
And the analysis found that the people in the stroke belt eat more fried fish, compared with Americans from elsewhere in the country.
 
Study details tell an alarming tale
The nationwide study produced seven key findings that link fried fish to increased stroke risk:
  • People from the stroke buckle were 11 percent less likely to meet the AHA recommendations, compared with volunteers from the rest of the country.
  • People in the rest of the stroke belt were 17 percent less likely to meet the AHA recommendations, compared with volunteers from the rest of the country.
  • People from the stroke belt were 32 percent more likely to eat two or more servings of fried fish, compared with volunteers from the rest of the country.
  • People in the stroke buckle were 17 percent more likely to eat two or more servings of fried fish.
  • Overall, people in the stroke belt ate an average of 0.68 servings of fried fish per week, compared to 0.64 in the stroke buckle and 0.62 in the rest of the country.
  • Compared with whites, African-Americans were more than three-and-a-half times more likely to eat two or more servings of fried fish per week.
  • People in the stroke belt ate less non-fried (i.e., stroke-preventive) fish per week – an average of 1.45 servings – compared with 1.52 servings in the stroke buckle and 1.63 servings in the rest of the country.
You may notice that people in the stroke buckle – which has the stroke belt’s highest stroke death rate – reported eating less fried fish and more non-fried fish, compared with people from the rest of the stroke belt.
 
That finding seems to undermine the connection between fried fish and stroke.
 
Yet the statistically stronger between fried fish and stroke held true for people in the stroke belt as a whole, versus people living outside of it
 
And the weaker link between stroke risk and fried fish intake the the coastal stroke buckle could be explained by other, protective differences in diet and lifestyle between people in the buckle and those in the rest of the belt.
 
As lead author Fadi Nahab, M.D., told The New York Times, fried fish was only one potential contributor to differences in stroke rate:
“The No. 1 thing is diet. And yet when we look at dietary differences in and out of the stroke belt, it’s hard to find any other than this one” (NYT 2010).
 
 
Sources
  • Emory University (EU). Eating Fried Fish Likely Factor in Strokes, Study Finds.Dec. 22, 2010. Accessed at http://shared.web.emory.edu/emory/news/releases/2010/12/eating-fried-fish-likely-factor-in-strokes-study-finds.html
  • Gillum RF, Mussolino ME, Madans JH. The relationship between fish consumption and stroke incidence. The NHANES I Epidemiologic Follow-up Study (National Health and Nutrition Examination Survey). Arch Intern Med. 1996 Mar 11;156(5):537-42.
  • He K, Rimm EB, Merchant A, Rosner BA, Stampfer MJ, Willett WC, Ascherio A. Fish consumption and risk of stroke in men. JAMA. 2002 Dec 25;288(24):3130-6.
  • Iso H, Rexrode KM, Stampfer MJ, Manson JE, Colditz GA, Speizer FE, Hennekens CH, Willett WC. Intake of fish and omega-3 fatty acids and risk of stroke in women. JAMA. 2001 Jan 17;285(3):304-12.
  • Mozaffarian D, Longstreth WT Jr, Lemaitre RN, Manolio TA, Kuller LH, Burke GL, Siscovick DS. Fish consumption and stroke risk in elderly individuals: the cardiovascular health study. Arch Intern Med. 2005 Jan 24;165(2):200-6. Erratum in: Arch Intern Med. 2005 Mar 28;165(6):683.
  • Myint PK, Welch AA, Bingham SA, Luben RN, Wareham NJ, Day NE, Khaw KT. Habitual fish consumption and risk of incident stroke: the European Prospective Investigation into Cancer (EPIC)-Norfolk prospective population study. Public Health Nutr. 2006 Oct;9(7):882-8.
  • Nahab F, Le A, Judd S, Frankel MR, Ard J, Newby PK, Howard VJ. Racial and geographic differences in fish consumption: The REGARDS Study. Neurology. 2010 Dec 23. [Epub ahead of print]
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