Women who eat fried chicken every day may be 13 per cent more likely to die prematurely than people who avoid these foods, a US study suggests.
Fried fish is only slightly better, with a seven per cent greater risk of premature death from all causes associated with one daily serving, the study found.
"Eating fried foods does increase total calorie intake and risk of obesity, which is related to an increased risk of death," said senior study author Wei Bao of the University of Iowa in Iowa City.
"However, in our analysis, we have accounted for total calorie intake, lifestyle habits, and obesity status," Bao said by email. "After controlling for these factors, the association of fried foods with all-cause death and cardiovascular death remained."
As many as one in three adults in North America eat fast food, usually fried, every day, Bao and colleagues note in the BMJ.
During frying, foods can lose water and absorb fat, which may make meals crunchier and more appetising but also encourage people to eat more than they should. Previous research has linked fried food to an increased risk of obesity, heart disease and diabetes, but the potential connection to premature death has been unclear.
For the current study, researchers examined diet questionnaire data from 106,966 women aged 50 to 79 who participated in the Women's Health Initiative study between 1993 and 2017.
On average, researchers followed each woman for about 18 years. During follow-up, 31,588 women died, including 9,320 who died of heart problems and 8,358 who died from cancer.
To assess fried food consumption, researchers looked at how often women reported eating certain items when they first enrolled in the study, including: "fried chicken"; "fried fish, fish sandwich and fried shellfish (shrimp and oysters)"; and other fried foods, such as French fries, tortilla chips and tacos.
After accounting for other factors that might hasten death such as limited education, inactivity and eating an overall unhealthy diet, researchers found that regularly eating fried foods was associated with a heightened risk of death from any cause and, specifically, from heart problems.
Women who ate at least one daily serving of fried chicken were 12 per cent more likely to die of heart problems than women who didn't eat fried food, the study found. Fried fish, meanwhile, was associated with a 13 per cent higher risk of death from heart problems.
But eating fried food didn't appear to impact the risk of dying from cancer.
Participants who ate fried foods more regularly tended to be younger, non-white, with less education and a lower income. They were also more likely to be smokers, exercise less and have a lower-quality diet.
The study wasn't a controlled experiment designed to prove that fried foods directly impact longevity. Another drawback is that it relied on women to accurately recall everything they ate.
Even so, the results offer fresh evidence that how food is prepared can have a big impact on health, said Dr Clyde Yancy of the Northwestern University Feinberg School of Medicine in Chicago.
"Poultry and fish are generally regarded as 'heart healthy' dietary choices but the process of frying changes the health consequences," Yancy, who wasn't involved in the study, said by email.
"When fried foods are consumed, the altered structure of those fats used for frying generates signals for more inflammation, more (hardening of the arteries) and higher blood sugars," Yancy added. "This only worsens when the fried food ingestion is associated with sugar sweetened beverages, high sodium and less fruit and vegetable intake."
Avoiding fried foods may be ideal, but some frying methods may be better than others, said Daniel Lackland, a researcher at the Medical University of South Carolina in Charleston who wasn't involved in the study.
"Elimination of trans fats is important," Lackland said by email. "Consuming foods prepared by grilling or baking would be the preferred choice - but if occasional fried foods are consumed, frying with safer oils such as olive oil would be a good way to go."