A study conducted at Shenzhen University, China found that for every four ounces of fried food eaten there's a measurable increase in heart disease risk. The study helps us understand why most nutritional experts assert that fried food, even when prepared at home, is still "processed" food. Some experts point to the fact that simply getting a person to replace McDonald's French fries with home fries made with coconut oil is a step in the right direction. Others point to the advantages of stir frying on low heat. These are fair points. However, if we step back from the gray areas of the "processed" debate, you can't avoid the fact that frying—especially at high temperature—changes food so drastically that it creates health risks. So, it's worth taking a look at precisely how frying changes food—and why it should be reserved for rare occasions. Frying creates a chemical bath When food is heated in oil at high temperatures, it undergoes chemical changes that do not occur during steaming, baking, or boiling: Acrylamides: This is a chemical that can form in plant-based foods (like potatoes or starchy vegetables) when they are cooked at high temperatures. The International Agency for Research on Cancer classifies acrylamide as a "probable human carcinogen." Advanced Glycation End-products (AGEs): These are compounds that are formed and promoted by high-heat cooking. AGEs are associated with oxidative stress and inflammation in the body. Oil oxidation: Even "healthy" cooking oils can become oxidized when subjected to prolonged high heat. The oxidation process creates free radicals, which are linked to cellular damage. Avoiding seed oils lowers the risk; however, all oils create free radicals to some extent when used for frying. Frying changes caloric density Frying acts as an efficient delivery system for fats. Even if the base food (whether meat or vegetable) is nutrient-dense, the process adds a significant amount of concentrated energy (calories) via the absorption of oil. In short, frying turns low-calorie-density foods into high-calorie-density foods. This change is enough to motivate many nutritionists to move fried foods from the "whole food" category to "junk food" category. Frying dilutes nutrients Frying can degrade heat-sensitive vitamins that are present in the raw ingredients. This is true most notably for Vitamin C and some of the B vitamins. Furthermore, the high fat content, when fried, often displaces the fiber or water content that would otherwise help with digestion and blood sugar regulation. This "processed" result is nutritionally inferior to the raw, steamed, or roasted versions of the same food. Study highlights dangers In the Shenzhen University study, researchers conducted a meta-analysis of 17 studies to examine the link between eating fried foods and cardiovascular disease risk. These accumulated studies involved over 560,000 people who experienced 36,727 cardiovascular events such as a heart attack or stroke. The researchers found that the individuals who ate the highest amount of fried food had a 28% greater risk of suffering a major cardiovascular event compared to individuals who eat the lowest amounts of fried food. The high fried food consumers also had a 22% higher risk of coronary heart disease and were 37% more likely to suffer heart failure. The researchers also revealed a definitive trend line connecting fried food to the three types of heart-health issues that they tracked: For every four ounces of fried food a person consumed the risk of cardiovascular events increases by 3%; the risk of coronary heart disease increases by 2%; and the risk of heart failure increases by 12%. The study was published in Heart in January 2021. - - - Source: BMJ Journals (Heart).
