Clinical researchers (AHRQ 1998, Borhani 1965, Clinical Advisor for Nurse Practitioners 2006 ) have long been calling much of the Southeastern United States, including Alabama, Arkansas, Louisiana, Mississippi, (and more recently East Texas-----see Ramshaw 2011) as part of a stroke belt, and the medical literature has long used the term “the Stroke Belt Buckle” for both North & South Carolina and Georgia.
But now, stories in the New York Times (Rabin 2009) and USA Today (Brophy Marcus 2010) , have heightened public awareness of that Stroke Belt & Belt Buckle, particularly with regard to the eating of fried fish (Bakalar 2011) as possibly a contributing dietary factor.
Are Stroke Belt Dwellers Not Getting Enough Fish-Provided Omega-3 Fatty Acids?
The key study (Nahab et al 2011) places no clear cut blame on any particular type of fish, but suggests that of the 21,675 study participants, only 5,022 ate the recommended two servings per week of fish high in omega-3 fatty acids, a nutraceutical associated with good cardiovascular health.
By this, the authors imply that the majority of Southerners were not eating fish like mackerel, herring, salmon (coldwater ocean-going species for the most part, which were cited as examples of fish one should eat to obtain omega-3s). This is not surprising since none are particularly common to Southern cuisine, nor are they quite as available in supermarkets, and in the case of salmon, not as affordable relative to alternative fish.
Additionally one feature of those Southerners with a higher rate of stroke was that many had two or more servings of other fried fish not so notably rich in omega-3s.
Where are Stroke Belt Dwelling Fried Fish Eaters Eating Their Fried Fish Meals?
To most people in the Stroke Belt ( I now count myself among their numbers) it would seem important for any study to be more definitive to distinguish between home-cooked and restaurant-cooked, in determining which fish are most likely to be involved in any study implicating fried fish, although it is not clear that the authors did this with the survey instrument that they used. The reason that "where the fish is typically eaten", is important is that both the type of fish and the type of frying vary, sometimes dramatically between home-cooked and restaurant-cooked, here in the South.
Are The Freshwater Fish Favored By Those In the Stroke Belt Somehow at Fault?
Home-cooked fish in the South means predominantly freshwater fish. First and foremost, it’s farm-raised catfish, then farm-raised tilapia, followed by sport-fished, wild-caught crappie or bass. Along the Gulf Coast, home-cooked saltwater fish like red snapper is also common.
Restaurant-cooked fish in the South vary further by whether one is eating at a large, generally nationwide chain, or at a locally-owned or regionally-concentrated operation.
The overall fisheries marketing consideration here in the South (and actually increasingly for the rest of the US), is that there is a strong preference among restaurant-goers for fish whose flesh is white and whose taste, unlike the taste of herring, mackerel, and sometimes salmon, is mild.
Fishy tastes and oily, dark flesh do not sell well in the South, and indeed, have been bred out of today’s farm-raised catfish, one of the reasons for its sustained popularity. Unfortunately, perhaps, oily, dark-fleshed fish are usually very rich in omega-3s.
But The Stroke Belt is Not the Only Place in the Country Where Fried Fish Relatively Lower In Omega-3s is Frequently Eaten
The local/regional fish found in the restaurants of the Stroke Belt are today overwhelmingly farmed catfish and farmed tilapia.
Wild-caught cod, haddock, and pollock, are sometimes available but are expensive and far more characteristic of homes and restaurants New England, New York, & New Jersey, than the South. (I lived my first 56 years in New England, so I know whereof I speak).
However, today’s restaurant pollock and haddock, whether served at local, regional, or national restaurants---- outside of the local, coastal New England market------ is much more likely to come from Alaskan waters than from New England, today).
Judging from their corporate websites, it is sometimes possible to sort trying to sort out which “mild, white fish” is used for larger restaurant chains. Given that “mild white fish” can vary quite a bit in terms of their omega-3 levels, it ought to make a difference if it is the omega-3s that matter the most.
Unfortunately for our purposes in tacking down which fish was in the “fish-wich,” so to speak, many national chains, particularly outside the South, use a number of differing fish interchangeably without necessarily cueing the consumer.
None of the following is to be taken as indicative of a lack of concern on the part of the restaurant chain for the wholesomeness of whatever fish it is. There is no proof that any of the species discussed is unsafe to eat, just that some fish have more omega-3s than others.
Denny’s appears to use an assortment of fish including pollock and “pangasius” (generally these are farmed catfish-like fish imported from Vietnam or the People’s Republic of China, but are not to be confused with the arguably much more closely monitored, more quality-controlled US farm-raised catfish.) Denny's also sometimes uses haddock.
Long John Silvers uses a similar variety of white, mild fish, but also include hake ( a relative of the cod family), and tilapia.
Wendy’s uses primarily cod.
Ruby Tuesdays uses the usual assortment of white fish, but has premium seafood entries that include farmed salmon and farmed trout. Of those, only the salmon and the trout would have notably higher omega-3 levels.
Are All Types of Frying Equally Bad, Assuming That It’s the Frying That’s the Problem?
The study’s authors suggest that frying seems to reduce or destroy natural omega-3 levels in the fish. But there is no indication if by "frying" the authors mean deep-fat frying, like French fries and donuts, or pan-frying as in pork chops or bacon.
As a practical matter in Southern kitchens, most home-cooked fish is likely to be shallow-pan-fried, and most restaurant fish is likely to be battered and deep-fat fried, although grilled fish is coming on strong, particularly at eat-in restaurants in national chains.
Do the Cooking Fats & Oils Matter More than the Fish Within Which They Were Fried?
In any case, if the infusion of oil caused by deep fat frying is the culprit, then this should be explicitly mentioned or separately analyzed.
It should be understood, however, that battered and deep-fried fish probably has a lot less penetration of the cooking oil into the fish than might be imagined, because the oil, if sufficiently hot when the battered fish is placed in it, quickly seals off the fish.
Nor do we know which homes or restaurants use butter, lard, partially hydrogenated semi-solid shortening oils (similar to Crisco) or polyunsaturated oils in liquid form.
This is likely to be a significant matter since, at various times, a number of these fats have been implicated as being unhealthy for the heart, while others (typically olive oil, sunflower oil, and safflower oil and certain other more exotic types, are regarded as downright heart-healthy).
Omega-3 Levels vs. Arachidonic Acid Levels In Fish
There is, an as yet, unresolved debate as to whether eating some fish with lower levels of omega-3 fatty acids but possibly higher levels of a somewhat similar fatty acid, called arachidonic acid (ARA) is as “heart healthy” as eating only high omega-3 fish.
Some farmed fish, particularly catfish and tilapia, have a higher ratio of ARA to omega-3s. Some authors (Weaver et al. 2008) suggest that ARA may promote inflammatory responses within the body, and that may have some implications for cardiovascular disease processes, although the experimental animals on which this position is based is the African green monkey (Parks et al 1990) whose physiology provides a good, but scarcely infallible road map to likely human consequences.
But other authors (Clandinin et al 2005) point out that ARA is demonstrably crucial to the development of infants and is actually added to infant formula.
Tests of significantly larger amounts of ARA in the diet of healthy adults showed no adverse consequences (Brenna & Diau 2007, Nelson et al 1997).
ARA seems to promote healthy immune responses (Kelley et al 1997) and cell and tissue repair (Bonnans & Levy 2007).
In a study of Japanese fishermen, who not only ate fish, but were given additional ARA (Kusumoto et al 2007) there was some adverse blood and platelet chemistry, but this was a rather extreme situation.
By extreme we mean that one would have to eat about five times as much US farm-raised tilapia, or eight times as much US farm-raised catfish, to get even close to the levels of ARA in the Japanese study (Nettleton 2008).
But this debate may be best resolved by a compromise suggested by Chilton (2008) one of the authors of the “fear of ARA ratios in some fish paper,” in answering a critique of that study. Perhaps, Chilton notes, there are simply certain people with chronic inflammatory diseases that might be specially advised to avoid certain fish, (or for purposes of our discussion, certain fish fried in some particular way), while the vast majority of people may eat fried fish gladly, particularly in preference to “bacon, hamburgers, or doughnuts.”
If Farmed Freshwater Fish Are the Problem, Can the Fish Be Farmed In A Different Way?
The answer is yes, if the fish is actually the problem, which is by no means clear. Including certain dried algae (Menghe et al 2009) in catfish feed would improve their lipid profiles beneficially, but whether or not this is commercially feasible in an industry that already has problems with its feed costs (Stankus 2010) or if the supply of the dried algae is sufficient has not yet been determined.
What Factors, Other Than Fried Fish, Might Be Involved in Making the Stroke Belt the Stroke Belt?
The answer is: There are so many posible confounding factors, in the study and in the Stroke Belt, that it would be hard to know when to stop counting.
Lower levels of education and income are also associated with the South and with strokes.
High blood pressure is associated with strokes and higher blood pressure is more common in the South.
Consumption of high saturated fats (particularly lard, pork, ham, bacon, etc.) is common in the South.
As is a high rate of diabetes, obesity, cigarette smoking, and salt consumption
Geography itself in some way, seems to play a persistent role in the incidence of stroke. People who are born in the South but live as adults in other parts of the country seem to have a persistently higher rate of stroke anyway (El-Saed & Kuller 2007, Glymour, Avendaño & Berkman 2007 ) and adults who were born and raised elsewhere who move to the South (much like myself) also have a raised probability of having a stroke (Glymour, Kosheleva & Boden-Albala 2009).
But we should not be too quick to blame somehow being in the Southern United States for causing strokes.
The US Stroke Belt is scarcely the only one in the world: Andalusia in Spain (Castilla Guerra, Del Fern & Marín-Martín 2010) has one of its own, and there is no evidence whatsoever that fried fish, farmed, freshwater, omega-3 poor or arachidonic acid high, has anything to do with it, even as many of the other factors discussed in the latter portion of this blog seem to come together, much as they do in the American South.
Tony Stankus FSLA, tstankus@uark.edu Life Sciences Librarian, Science Coordinator & Professor
University of Arkansas Libraries MULN 233 E
365 North McIlroy Avenue
Fayetteville AR 72701-4002
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Fax: 479-575-4592
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