Evidence review sees deep risks in fried foods — even fried fish 01/31/2019
Many folks find fried foods hard to resist, thanks to the oily, crunchy lusciousness of the batter or breading.
About one in three American adults eat fast food every day, and a significant proportion of it — like fried chicken, fish-fillet sandwiches, onion rings, and French fries — was fried in oil.
And country fairs feature a bizarre variety of deep-fried fare, ranging from butter sticks, whole hamburgers, ice cream, and jelly beans to scorpions and alligator meat!
There’s a good deal of evidence that fish-rich diets reduce the risk for stroke: see Does Fish Fight Stroke?, Stroke: An Update on Fish and other Factors, and Do Fish Beat Fish Oil for Beating Stroke?.
Even though a food like chicken or fish may be generally healthful, the oil-soaked, white-flour coating on the fried version of a healthful food can partially or completely neutralize its health benefits.
And the results a Midwestern scientific team reported after they analyzed data from a very large study in older women paint a rather alarming picture of fried foods.
Before we get to those disturbing findings — which even apply to fried fish — let’s take a quick look at the findings of the most recent evidence review, published in 2015.
Boston team’s evidence review raised red flags
Three years ago, researchers from Boston’s Brigham and Women’s Hospital published their review of the evidence concerning the cardiovascular health impacts of fried foods (Gadiraju TV et al. 2015).
Surprisingly, as they wrote in their review, “Fried food consumption and its effects on cardiovascular disease are still subjects of debate.”
Despite their unhealthful image, there hasn’t been consistent evidence linking greater consumption of fried foods to higher risks for specific conditions: cardiovascular disease, heart failure, diabetes, or hypertension.
While some population studies found links between greater consumption of fried foods and greater cardiovascular and other risks, others either found no such links, or the apparent risks depended on people having other significant risk factors.
In other words, it wasn’t clear whether people's fears of fried foods — and comedians’ frequent jokes about them — are really justified.
And, given recent reversals in the fortunes of saturated fats — whose heart-unhealthful reputation was always oversimplified and has been substantially revised — the presumed risks of fried foods no longer seemed so certain.
Researchers at Harvard-affiliated Brigham and Women’s Hospital scrutinized the available evidence concerning the effects of fried foods on cardiovascular disease, diabetes, hypertension, and obesity.
Most of the available data comes from epidemiological studies, in which people answered diet questionnaires designed to determine their typical consumption of various foods.
But the Boston team's analysis detected links that suggest real risks. As they wrote, “There is strong evidence suggesting a higher risk of developing chronic disease when fried foods are consumed more frequently (i.e., four or more times per week).”
The Boston group also noted “major gaps in the current literature”, including a lack of details about the effects of different frying oils, types of fried food, frying methods (deep-frying versus pan-frying), temperatures and durations of frying, and how often oils are reused.
They also found that many prior studies failed to take people’s overall dietary patterns into account when they analyzed the health effects of eating fried foods frequently.
Now, the results of a new evidence review from Midwestern researchers seems to paint a more incriminating picture of fried foods.
New study reveals deep fried-food risks for women
The new study comes from researchers at the University of Iowa and Washington University in St. Louis (Sun Y et al. 2019).
As we said at the outset, evidence about the risks of eating fried foods frequently is limited and debatable.
So, this Midwestern team decided to review data from a very large study among women to look for any statistical links (correlations) between fried food and death from any cause — especially heart- and cancer-related death.
They analyzed self-reported data about the diets of 106,966 women aged 50 to 79 who’d participated in the Women's Health Initiative (WHI) study.
The WHI was an epidemiological study that took place between 1993-1998, with the participating women being followed for almost a decade.
The researchers collected data on the women's total consumption of fried foods, and their consumption of specific fried foods, including chicken, fish, fish sandwiches, shellfish (shrimp and oysters) and other fried foods, such as French fries, tortilla chips, and tacos.
Women who reported eating fried foods more frequently tended to be younger, non-white, and less educated with lower incomes. They were also more likely to be smokers, to exercise less and to report eating a lower-quality diets overall.
After taking these and other potentially influential lifestyle factors into account, the researchers’ statistical analysis linked regular eating of fried foods to a heightened risk of death from any cause.
Their analysis also linked more frequent eating of fried foods to greater risk for heart-related death: compared with those who did not eat fried food, women who reported eating one or more servings a day were 8% more likely to die from a heart-related cause.
And, despite the relatively healthful nature of chicken and seafood, fried chicken and fried fish or shellfish were linked to a higher risk for heart-related death — particularly among younger women (aged 50-65 years) in the study.
These were their estimates of the risks — compared with eating no fried food — of eating one or more servings of various fried foods daily:
- Fried chicken: 13% higher risk of death from any cause and 12% higher risk of heart-related death.
- Fried fish or shellfish: 7% higher risk of death from any cause and 13% higher risk of heart-related death.
Somewhat surprisingly, the researchers found no evidence linking fried food with greater risks for cancer-related death.
It’s important to note that the WHI was an epidemiological study, so it can only detect statistical links, and cannot prove a cause-effect relation between fried foods and specific health outcomes.
However, the authors stressed the large size and diversity of the study sample, and believe that, as they wrote, “… we have identified a risk factor for cardiovascular mortality that is readily modifiable by lifestyle.”
And their findings led them to a rational recommendation: “Reducing the consumption of fried foods, especially fried chicken and fried fish/shellfish, may have clinically meaningful impact[s] across the public health spectrum.”
That advice is backed by recent findings from the University of Alabama and Atlanta’s Emory University, which linked fried fish to the higher rates of stroke seen among African-Americans and in America’s so-called “stroke belt”, which encompasses Alabama, Arkansas, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, South Carolina, and Tennessee.
As the authors of that study wrote, “Fried fish intake of two or more servings per week is associated with an increased risk of cardiovascular events. Given the increased intake of fried fish in the stroke belt and among African Americans, these data suggest that dietary fried fish intake may contribute to geographic and racial disparities in CVD.” (Nahab F et al. 2016)
Their finding fits with prior reports on the dangers of eating fried fish frequently: see Fried Fish Seen to Raise Stroke Risk, Women's Heart Risk Cut by Fish but Frying it Outweighs the Benefit, and Deep-Frying Blocks the Heart Benefits of Fish.
Why would fried fish be risky, when fish itself is highly healthful?
The answer to this puzzling question probably lies in the nature of deep-frying, and — to a lesser extent — in the types of fish fried by restaurants and fast-food chains.
Deep- or pan-frying food in vegetable oil combines two seriously unhealthful elements:
- Refined white flour.
- Vegetable oil (often reused) that’s high in polyunsaturated omega-6 fats gets heated to high temperatures while exposed to air, which tends to oxidize (degrade) its unsaturated fats.
The downside of many frying oils
The unhealthful nature of refined white flour is well documented, but what’s so bad about the vegetable oils — typically soy, corn, cottonseed, and regular (i.e., not “high-oleic”) sunflower or safflower oil — in which most fried food gets cooked?
Those oils are very high in omega-6 fats. And an ever-growing body of evidence details the dangers of diets — such as the standard American diet — characterized by large amounts of omega-6 fatty acids and very small amounts of seafood-source omega-3 fatty acids.
For more on the topic of America’s unhealthful “omega imbalance”, see the Omega-3/6 Balance page of our website — which hosts the Out of Balance video (featuring interviews with leading researchers) — and relevant news reports in the Omega-3/Omega-6 Balance section of our newsletter archive.
Which fish? The answer matters
The type of fish being fried also matters, and many restaurants and fast-food chains use the least healthful kinds.
While some use Alaskan pollock, which has substantial amounts of omega-3 fatty acids and a healthful omega-3/6 fat balance — many use catfish or tilapia, which have very few omega-3 fats, and highly unhealthful omega-3/6 fat balances.
For more on that topic, see Tilapia Taken to Task, Farmed Fish Possess Unhealthful Fat Profiles, and Farmed Salmon's Diet Yields Unhealthful Cardiovascular Effects.
So, it makes sense to eat plenty of fish to support optimal heart and overall health — just avoid the fried variety!
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- Djoussé L, Petrone AB, Gaziano JM. Consumption of fried foods and risk of heart failure in the physicians' health study. J Am Heart Assoc. 2015 Apr 23;4(4). pii: e001740. doi: 10.1161/JAHA.114.001740.
- Gadiraju TV, Patel Y, Gaziano JM, Djoussé L. Fried Food Consumption and Cardiovascular Health: A Review of Current Evidence. Nutrients. 2015 Oct 6;7(10):8424-30. doi: 10.3390/nu7105404. Review.
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- Nahab F, Pearson K, Frankel MR, Ard J, Safford MM, Kleindorfer D, Howard VJ, Judd S. Dietary fried fish intake increases risk of CVD: the REasons for Geographic And Racial Differences in Stroke (REGARDS) study. Public Health Nutr. 2016 Dec;19(18):3327-3336. Epub 2016 Jun 24.
- Sun Y, Liu B, Snetselaar LG, Robinson JG, Wallace RB, Peterson LL, Bao W. Association of fried food consumption with all cause, cardiovascular, and cancer mortality: prospective cohort study. BMJ. 2019 Jan 23;364:k5420. doi: 10.1136/bmj.k5420.