But the study also suggested that not all frying oils are equally dangerous, or pose the same health risks.
The research team, led by the Harvard School of Public Health’s Department of Nutrition and Epidemiology, analyzed diet and disease data from a group of more than 100,000 women and men. They concluded that those who ate fried foods four to six times a week, saw their risk for developing Type 2 diabetes spike 39%, compared to those who ate fried foods less than once a week. Coronary disease jumped by 23% in the same group.
That level of consumption of fried foods equates to almost one meal of fried food every day. But the real culprit in the study is the widespread use of the kind of oil used to fry foods – partially hydrogenated vegetable oil, the king of trans-fat. Margarine and shortening are hydrogenated vegetable oils as well.
“Trans fat is made by adding hydrogen to vegetable oil through a process called hydrogenation, which makes the oil less likely to spoil. Using trans fats in the manufacturing of foods helps foods stay fresh longer, have a longer shelf life and have a less greasy feel.
Scientists aren’t sure exactly why, but the addition of hydrogen to oil increases your cholesterol more than do other types of fats. It’s thought that adding hydrogen to oil makes the oil more difficult to digest, and your body recognizes trans fats as saturated fats.” – Mayo Clinic.
Oils with trans-fats are the worst for you
All cooking oils break down when they’re heated to the temperatures required to fry foods. Most importantly, the structure of the fatty acids change. Oils with trans-fats create a high level of oxidative stress in our bodies, which means that we can’t neutralize all of the antioxidants these fats create. As a result, the substances thrown off by the heated oils are stored in our fat tissues and lead to a host of health problems, including Type 2 diabetes and heart disease, as well as high cholesterol, obesity, and hypertension.
Especially troublesome is the fact that restaurants re-use these oils to fry and fry again, which makes them even more dangerous. It’s one of the reasons New York City cracked down on the use of trans-fats in restaurants. The benefit to restaurants is that they last longer and can be reused, but unfortunately, that also makes them toxic for humans.
To be fair, many restaurants have reduced their use of trans-fats in cooking oils, but they’re still prevalent in some chains, and ubiquitous in prepared foods.
A co-author of the study, Leah Cahill, research fellow in nutritional sciences at the Harvard School of Public Health, says that past research hints that cooking oils which are free of trans-fats may pose fewer health risks. But as far as which fried foods you should eat, and which ones you shouldn’t, that’s too complex a question.
If you’re really craving fried chicken tonight, cook it at home in peanut oil (as in this recipe from Bon Appetit), olive oil, or even lard. Any of these cooking oil choices is safer than buying it from a fast food restaurant which uses the same oils over and over again.
But of course, fried chicken is a heavyweight when it comes to calories, regardless of trans-fats or good fats. So if you’re on a weight management program, it’s probably a road you shouldn’t go down at all.