Why Are Fried Foods Bad for You? (The Real Reason) | Zero Acre Farms

Why are Fried Foods Bad for You? (The Real Reason)

September 22, 2022

WRITTEN BY: Corey Nelson

Article at a Glance

Introduction

Fried food has been a culinary staple for hundreds, if not thousands of years, with some evidence of pan frying reaching as far back as ancient Egypt.

Until the 20th century, most people cooked fried foods in lard or other animal fats, but all of that ended when inexpensive, mass-produced industrial seed oils gained popularity in the last hundred years or so. Today, almost all fried food is made with seed oils like soybean, sunflower, corn, or peanut oil.

Many people understand that fried foods are associated with health risks like cardiovascular disease and obesity. But not many people understand exactly why fried foods are bad for you.

In this article, you'll learn why common fried foods are harmful, the increased risks of health problems associated with consuming them, and what you can do instead to make frying healthier.

Why Are Fried Foods Bad For You?

Fried foods pack a one-two punch: they're made using unhealthy, inflammatory seed oils, and they're cooked at high temperatures that damage those oils and cause additional problems. We'll start by unpacking the oils that are most commonly used in fried foods and the issues they cause.

Seed oils, often called industrial seed oils, are a subset of vegetable oils derived from seeds. These oils are high in omega-6 linoleic acid, which is associated with health problems, including inflammation, obesity, and cardiovascular disease.

These oils are almost always derived from the seeds of crops and include:

Because of their high linoleic acid content, these oils aren’t great for your health, even when consumed unheated or lightly heated. However, frying with these oils appears to increase the risk of health problems even further compared to consuming them at room temperature or lightly heated.

The reason is that seed oils high in linoleic acid are unstable, which means they break down into harmful byproducts during manufacturing, storage, transportation, and especially during high-heat frying.

And it's the creation of these compounds that is responsible for the increased harm associated with fried food consumption.

The Problems With Heating and Reheating Vegetable Oils

Unlike home cooking, many restaurants reuse frying oil hundreds of times for convenience and cost savings. This practice isn't condoned, but it's also not illegal.

A 2018 study on restaurant oil quality found that over 80% of randomly selected restaurant frying oil was oxidized beyond the recommended limit. Oxidation is a chemical reaction that involves the loss of an electron and creates harmful, toxic compounds in fried foods.

Seed-derived "vegetable oils" high in omega-6 linoleic acid, which are the most common frying oils, begin to break down rapidly from the first time they’re heated and get worse with additional reheating. For example, research shows that after only 30 minutes of heating, levels of toxic, carcinogenic aldehydes in corn oil and sunflower oil increase by 1,000%.

Research also shows that as much as 15% of the fatty acid content of restaurant-prepared french fries is oxidized. And oxidized omega-6 fatty acid byproducts like hydroxylinoleate (HODE) and 4-hydroxynonenal (4HNE) are closely linked with obesity, inflammation, and cardiovascular disease.

Finally, frying and reheating vegetable oils can raise levels of harmful trans fats by 1,000-2,000% or more, increasing trans fats to 5% of the total fatty acid content in frying oils. While artificial trans fats are now banned as food ingredients in many regions, these rules don’t apply to fried foods because the trans fats are formed during the cooking process.

A large meta-analysis including millions of participants found that high trans fat intake is associated with a 34% higher risk of all-cause mortality (death), 28% higher risk of cardiovascular mortality, and 21% higher risk of cardiovascular disease.

Health Problems Associated with Foods Fried in Seed Oils

It’s no secret that fried foods aren’t exactly healthy, but to what extent are they harmful? Studies link fried food consumption with obesity, cardiovascular disease, type 2 diabetes, gut health issues, reduced exercise performance, problems with fertility and pregnancy, and an increased risk of cancer.

Obesity, Caloric Density, and Omega-6 Fats

Fried food consumption is associated with higher obesity rates, even when adjusting for other factors like caloric intake. In other words, "caloric density" (the higher calorie content of fried foods) isn't the only factor behind weight gain when it comes to fried foods.

Studies suggest that potato chips and french fries result in 3 to 6 times more weight gain than boiled, baked, or mashed potatoes despite having the same caloric content. The primary difference is that chips and fries are generally fried in seed oils high in omega-6 linoleic acid, while boiled, baked, and mashed potatoes typically contain other fats that are low in linoleic acid (such as butter or cream).

And a 2007 study of over 33,000 men and women aged 29-69 found that high consumption of fried foods was associated with a 26% higher risk of general obesity for men, 25% higher risk of general obesity (large waist circumference) for women, 17% higher risk of central obesity in men, and 27% higher risk of central obesity in women.

Cardiovascular Disease and Mortality

A large 2021 meta-analysis (study of available studies) in BMJ Heart found that a high intake of fried foods increases the risk of major cardiovascular events by 28%, coronary heart disease by 22%, stroke by 37%, and heart failure by 37%.

And in a five-year study of over 100,000 women aged 50-79, consuming fried foods once or more per week was associated with a 13% higher risk of all-cause mortality (death) and a 12% increased risk of cardiovascular mortality occurring at any time during the study.

In a 2018 study of people who had survived a myocardial infarction (heart attack), compared to control participants who hadn't had a heart attack, frequently consuming fried foods from restaurants was associated with a 26-58% higher risk of heart attacks. The researchers found that people used the same types of oil at home as were used in restaurants — soybean, sunflower, and palm oil. Therefore, the main difference that might explain the disparity in effects was the higher frying temperatures and reuse of cooking oil that occurs in restaurants.

Metabolic Health and Diabetes

The changes that occur during frying, including oxidation, polymerization (which includes acrylamide formation), and hydrogenation (trans fat formation), can have negative effects on metabolic health.

In a 2014 questionnaire-based study of over 111,000 participants, participants who ate fried food 4-6 times per week had a 39% higher rate of type 2 diabetes, and those who consumed fried foods seven or more times per week had a 55% increased risk compared to people eating fried foods less than once per week.

Gut Health and Digestion

Compounds created during frying with seed oils may negatively affect your microbiome and cause or worsen inflammatory disorders of the gut (such as inflammatory bowel disease (IBD)).

In a 2019 paper published in the American Journal of Clinical Nutrition, researchers found that consuming fried foods was associated with lower diversity of the microbiome (gut bacteria and other microorganisms). And low microbiome diversity is associated with reduced immunity, digestive problems, and other health issues.

Athletes and Physical Performance

Considering their adverse health effects, it's unsurprising that common fried foods might be bad for athletic performance. A separate 2021 study tested the effects of dietary acrylamide (a harmful, carcinogenic compound formed during frying) on physical performance. Subjects who consumed the most acrylamide performed poorly compared to those who ate the lowest amounts.

Pregnancy Risk Factors

Research links fried food consumption before and during pregnancy with a higher risk of gestational diabetes as well as increased weight gain during pregnancy.

Cancer

In a case-control study matching 2,579 cancer patients with 2,277 control subjects, high fried food intake was associated with a 1.3- to 2.3-fold increased risk of prostate cancer.

Healthier Alternatives to Traditional Frying Methods

With the scientific literature showing that eating restaurant-fried foods even once per month can significantly increase the risk of serious diseases like diabetes and cancer, you might conclude that there's no place for fried foods in a healthy diet.

That’s because when you're cooking at home, you're not heating oil all day long or reusing it hundreds of times, so you're not producing harmful compounds to the same degree as restaurants.

The second most important factor is the type of cooking oil you use to fry at home. Seed oils (like soybean, sunflower, peanut, corn, grapeseed, canola, cottonseed, and "vegetable oil blends") are still a problem whether or not you're frying or reusing your oil.

And as a 2012 study published in the prestigious British Medical Journal found, replacing industrial seed oils with healthier alternatives prevents the negative health impact of deep frying foods.

Be sure to choose better frying oils that also suit your culinary needs. The best options are fats low in polyunsaturated fats with good thermal stability, traditional examples of which include olive oil, avocado oil, coconut oil, and most animal fats.

The Takeaway

The statistics on the negative health impacts of fried food are extremely concerning. Over one-third of American adults consume foods, typically deep fried, from fast food restaurants every day.

Even if you're only eating fried foods from restaurants once or twice a month, your risk of certain health problems may increase.

And eating them several times per week or more is linked with inflammation, weight gain, cardiovascular disease, metabolic issues, gut disorders, decreased physical performance, and cancer.

Luckily, you can avoid these issues by avoiding restaurants that use seed oils for frying and instead fry food at home without seed oils. You also won't be reusing oil hundreds of times, so you're not exposing yourself to high levels of toxic frying byproducts like aldehydes.