If you are using an air fryer in any of the four ways described below, you may be unknowingly reducing its nutritional benefits and increasing your risk of health problems. The air fryer has become an increasingly popular kitchen appliance in many households due to its ability to quickly prepare food with less oil. However, not everyone uses it correctly, which can lead to serious consequences.

According to Dr. Saurabh Sethi, a digestive health expert trained at Harvard and Stanford, how you use your air fryer doesn’t just affect the taste of your food—it also impacts your nutrition and overall health. He identifies four common mistakes in using an air fryer that lead to nutrient loss and increase the risk of poisoning, illnesses, and even cancer:

1. Choosing the Wrong Foods to Cook in the Air Fryer

Certain foods, such as leafy greens, very thin or delicate items, or fatty meats, when cooked at high temperatures in an air fryer, can produce harmful substances like polycyclic aromatic hydrocarbons (PAHs), which are known carcinogens. Soft leafy vegetables or very thin foods can easily burn and produce unpleasant odors, while fatty cuts of meat, such as pork belly, can cause flare-ups and even fire hazards. Additionally, using spoiled or improperly thawed foods can lead to severe food poisoning if cooked in an air fryer.

Instead, Dr. Sethi recommends selecting suitable foods that have been properly cleaned and prepared before cooking. Frozen foods, for example, should be thoroughly thawed according to instructions to ensure even cooking and to prevent bacterial growth.

2. Not Preheating the Air Fryer Before Cooking

Many people develop the habit of placing food directly into the air fryer without preheating, thinking it does not affect the quality of the food. However, like an oven, an air fryer requires preheating—usually for about 3 to 5 minutes—to ensure food cooks evenly. Skipping this step may cause food to be unevenly cooked, with the exterior being overly dry or burnt while the interior remains undercooked, which can allow harmful bacteria such as Campylobacter and Salmonella to survive. These bacteria can cause intestinal infections and food poisoning.

Moreover, failing to preheat can reduce the crispiness of the food, degrade its nutritional value, and extend cooking times unnecessarily. Dr. Sethi advises always preheating the air fryer to achieve better taste, safety, and nutrition retention.

3. Using the Wrong Amount or Type of Oil in an "Oil-Free" Appliance

Although called an "oil-free" fryer, this does not mean you should completely avoid using oil. Some foods, like vegetables or lean meats, may dry out and lose fat-soluble vitamins such as A, D, E, and K if cooked without any oil. Conversely, adding too much oil can cause excess oil to drip onto the heating element, potentially producing toxic smoke and acrylamide—a compound linked to cancer when accumulated over time.

Dr. Sethi warns that reusing cooking oil multiple times at high temperatures generates free radicals, which accelerate aging and increase the risk of chronic diseases like cancer and atherosclerosis. Therefore, it’s safest to use a minimal amount of oil only when necessary, and to prefer oils with high smoke points such as olive oil or canola oil to reduce toxin formation.

4. Not Cleaning the Air Fryer Thoroughly After Each Use

This is a very common mistake, especially when switching between different types of foods in the same device. Residual food particles and oil left inside the air fryer can spoil, altering the taste and nutritional quality of subsequent meals and increasing the risk of burning and smoke generation. Additionally, leftover grease creates an ideal environment for bacteria to multiply, which can lead to food poisoning.

Dr. Sethi emphasizes the importance of cleaning all removable parts of the air fryer after each use with hot water and dishwashing detergent to maintain hygiene and extend the appliance’s lifespan. Neglecting this cleaning can cause buildup that burns during the next cooking cycle, releasing harmful smoke and carcinogenic compounds like benzopyrene.

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Additional Recommendations for Safe and Healthy Air Fryer Use

• Avoid Overcrowding the Basket: Overfilling the air fryer can block air circulation, leading to uneven cooking and increased risk of bacterial contamination.

• Use Appropriate Cooking Temperatures: Follow recommended temperatures for different foods to avoid burning or undercooking.

• Monitor Cooking Times: Different air fryer models may require adjustments in cooking duration to prevent nutrient loss and food degradation.

• Store Leftovers Safely: Promptly refrigerate any leftovers to minimize bacterial growth before reheating.

By following these tips and avoiding common mistakes, you can maximize the health benefits of your air fryer while minimizing risks of poisoning, illness, or even kitchen accidents.