Not all oils are created equal when it comes to cooking. Some oils break down under heat, releasing harmful compounds and losing their nutritional value. Knowing which oils to avoid at high temperatures – and why – can make a real difference for your health.

The key factor: smoke point and stability
Every oil has a smoke point – the temperature at which it starts to break down and produce smoke. When an oil reaches its smoke point, it releases free radicals and other potentially harmful substances. Oils high in polyunsaturated fats (such as soybean, corn, and grapeseed oils) are particularly unstable at high heat.

Five oils that are not ideal for cooking

1. Flaxseed oil – Extremely high in polyunsaturated fats, flaxseed oil has a very low smoke point (around 225°F / 107°C). It is best used cold in salad dressings or drizzled over finished dishes. Heating it destroys its beneficial omega‑3 fatty acids.

2. Walnut oil – Like flaxseed oil, walnut oil is rich in delicate polyunsaturated fats. It has a low smoke point and becomes bitter when heated. Use it only for cold applications.

3. Unrefined coconut oil – While coconut oil is saturated and more stable than many oils, unrefined (virgin) coconut oil has a smoke point of about 350°F (177°C), which is lower than many people realize. It can be used for light sautéing but not for deep frying.

4. Extra virgin olive oil – Despite its popularity, extra virgin olive oil has a moderate smoke point (around 375°F / 190°C). It is fine for low to medium heat cooking, but high heat can degrade its flavor and beneficial antioxidants. For high heat, use refined olive oil or avocado oil.

5. Sesame oil – While flavorful, unrefined sesame oil has a smoke point around 350°F. It is best used for finishing dishes or light stir-frying. Refined sesame oil has a higher smoke point but loses much of its distinctive taste.

What to use instead for high-heat cooking

For frying, searing, and high-heat baking, choose oils with high smoke points and stable fat profiles:

• Avocado oil – Smoke point around 520°F (271°C), rich in monounsaturated fats.
• Refined coconut oil – Smoke point around 400°F (204°C), stable for medium-high heat.
• Ghee (clarified butter) – Smoke point around 485°F (252°C), lactose‑free and flavorful.
• Refined olive oil – Smoke point around 465°F (240°C), good for roasting and baking.

A simple rule of thumb

Use cold-pressed, unrefined oils for cold dishes and low‑heat cooking. For frying and high‑heat applications, choose refined oils or fats with high smoke points.

A final note

No single oil is perfect for every use. Keeping a few different oils in your kitchen allows you to choose the right one for each cooking method – and to preserve both flavor and health benefits.