It’s no secret that fried food isn’t good for you. But a new study published in The BMJ details exactly how eating these foods may affect your health over time — and spells out which kinds may be the worst for you.
“People know fried food may have adverse health outcomes, but there is very little scientific evidence to demonstrate what the long-term adverse outcomes are for eating fried foods,” says Dr. Wei Bao, an assistant professor of epidemiology at the University of Iowa College of Public Health and a co-author of the study. “In general, we found that fried food consumption is associated with overall mortality.”
The researchers looked at about 20 years’ worth of data for almost 107,000 older women in the U.S., ages 50-79. All of the women were part of the Women’s Health Initiative study, and they filled out one detailed questionnaire about their dietary habits in the 1990s. Their health was tracked by researchers until 2017, and during that time more than 31,500 people died.
Those who reported eating at least one serving of fried food per day had about an 8% higher chance of dying early, compared to women who said they did not eat any, according to the study. They also had a 8% higher chance of dying specifically from cardiovascular disease.
However, fried food consumption did not seem to correspond to a higher risk of dying from cancer, despite some past research that has connected the two. “We know diet is important for cancer prevention or cancer survival, but not all of the dietary components [seem to be equally important],” Bao says.
Fried chicken and fried fish were more strongly linked to early death than other fried foods, which the researchers grouped in a miscellaneous category including French fries, crackers, tortilla chips and snacks. The strength of the association may be because people simply consume more fried chicken or fish, Bao says, or because of differences in how those foods are prepared. For example, many restaurants reuse oil when they cook foods like fried chicken, which Bao says may increase the number of harmful byproducts transferred to the food. Meats also tend to be more deeply fried than many snack foods.
However, that finding (unfortunately) doesn’t absolve French fries. Since they were lumped into the miscellaneous group, the researchers weren’t able to look specifically at how French fries individually affected health — and it’s possible that their risks were obscured by comparably healthier foods in the “other” category, like crackers or fried plantains, Bao says. Past research has connected French fries to cancer and a higher mortality risk.
Still, Bao says his study is among the first to look at how eating any type of fried food affects mortality risk over time. The only other one he’s aware of, he says, was conducted in Spain in 2012, and did not find a correlation between fried foods and a higher death risk. This may be because more Spanish people prepare their food at home, rather than eating it in restaurants, and choose healthier frying oils, such as olive oil, Bao says.
In the new study, the researchers accounted for factors like medical history, demographics, smoking, drinking habits and overall diet quality, in an effort to isolate the effects of fried foods. But an observational study can a never prove cause and effect, and the authors note that it’s impossible to rule out the impact of other factors that affect health.
Another limitation of the study is that it only assessed dietary habits once, so it didn’t reflect how women may have changed their diets over time. Nonetheless, Bao says he believes that the findings are strong and likely apply to populations other than older women, even though the data did not specifically address other groups.
“We didn’t have any reason why the effects may differ by age, or even by gender,” Bao says. “I would suspect the association may be similar among younger women or even among men.”
Many other studies have linked fried foods to health issues including obesity, Type 2 diabetes and heart disease, but researchers estimate that nearly 40% of Americans eat fast food on any given day.