Which Oil Is Not to Heat? The Guide to Low Smoke Point Oils

December 2, 2025 •

4 min read

Knowing which oil is not to heat is crucial, as exceeding an oil's smoke point degrades beneficial properties and creates harmful compounds. This knowledge is especially important for oils rich in delicate polyunsaturated fats, ensuring safety and nutritional value.

Quick Summary

Heating low smoke point oils, such as flaxseed or walnut oil, can damage their delicate compounds, leading to a loss of nutrients and possibly dangerous byproducts. The best way to use these oils is in uncooked applications.

Key Points

Low Smoke Point Oils Should Not Be Heated: Oils like flaxseed and walnut have low smoke points and contain delicate fats that break down at high temperatures, producing harmful byproducts.
Use Low Heat Oils Raw: Use oils like flaxseed, walnut, and hemp seed for finishing dishes, salad dressings, or smoothies to preserve nutrients.
The Smoke Point Matters: Exceeding an oil's smoke point releases free radicals and toxic compounds, resulting in a bitter taste and potentially harmful health effects.
Refining Increases Stability: Refining oils removes impurities that lower heat tolerance, leading to a higher smoke point.
Best Oils for High-Heat Cooking: Refined avocado oil, ghee, and refined coconut oil are suitable for high-heat cooking methods due to their stability.
Proper Storage Extends Shelf Life: Store sensitive oils in a cool, dark place to prevent them from becoming rancid.

Understanding the Smoke Point of Cooking Oils

The smoke point is the temperature at which an oil begins to break down, resulting in visible smoke. This breakdown changes the oil's chemical structure, releasing harmful free radicals and other toxic compounds, such as acrolein, that can cause a bitter taste. For health-conscious cooks, selecting the right oil for the correct use is essential. Oils with high smoke points, like refined avocado or sunflower oil, are suitable for high-heat cooking methods such as frying and searing. Oils with low smoke points are best used unheated to preserve their flavors and delicate compounds.

Polyunsaturated Fats and Heat Stability

The stability of an oil when heated is determined by its fatty acid composition. Oils high in polyunsaturated fats (PUFAs) are the least stable when heated. PUFAs contain more chemical bonds that are vulnerable to high temperatures, making them prone to oxidation and rancidity. Many seed oils fall into this category. Although some may have a relatively high smoke point, their thermal instability means they can still create harmful byproducts even before smoke appears.

Oils That Should Not Be Heated

Flaxseed Oil: This oil, rich in alpha-linolenic acid (ALA), an omega-3 fatty acid, is very sensitive to heat, light, and oxygen. It has a very low smoke point of 225°F (107°C) and is not suitable for cooking. It should be used raw in salad dressings, dips, or added to smoothies after blending.
Walnut Oil: This flavorful oil, heavy in polyunsaturated fat, should not be heated. With a low smoke point of about 320°F (160°C), cooking with it will ruin its delicate, nutty flavor and cause oxidation. It is best for finishing dishes or cold preparations.
Hemp Seed Oil: Like flaxseed oil, hemp seed oil contains a high concentration of sensitive fatty acids. It has a low smoke point and a distinct flavor that heat compromises. Store it in the refrigerator and use it exclusively in cold applications.
Unrefined Oils: The refining process removes impurities and free fatty acids that can cause oil to smoke, thus increasing its smoke point. This means that unrefined or 'virgin' versions of many oils, such as virgin coconut oil or extra virgin olive oil, have a lower smoke point than their refined counterparts and are more susceptible to heat damage.

Comparison of Oils: Low vs. High Smoke Points


Feature	Oils Not to Heat (Low Smoke Point)	Oils Suitable for Heat (High Smoke Point)
Examples	Flaxseed oil, Walnut oil, Hemp seed oil	Avocado oil (refined), Canola oil, Refined coconut oil
Fatty Acid Profile	Rich in polyunsaturated fats	Rich in monounsaturated or saturated fats
Smoke Point	Below 350°F (177°C)	Above 400°F (204°C)
Stability	Thermally unstable	Thermally stable
Best Use	Salad dressings, dips, finishing dishes, smoothies	Sautéing, frying, roasting, searing

Healthier Alternatives for Various Cooking Methods

For those who want to cook without negatively affecting their health, several stable oil options are available. The best choice depends on the specific cooking method and preferred flavor. For everyday, medium-heat cooking, extra virgin olive oil is a good option, though its lower smoke point compared to refined olive oil means it shouldn't be used for deep-frying. For high-heat applications like searing or stir-frying, refined avocado oil is a top choice due to its high smoke point. Another stable option for high-heat cooking is clarified butter, or ghee, which has had its milk solids removed.

Maximizing Nutritional Value

Using low smoke point oils correctly is key to maximizing their health benefits. Many of these oils, particularly flaxseed oil, are prized for their omega-3 content and anti-inflammatory properties. Heating these oils can destroy these delicate fats and also produce inflammatory compounds. By understanding which oils are not to heat, you can ensure that you are making the healthiest culinary choices possible, using each oil according to its specific chemical properties. Storing these oils properly, away from heat and light in dark bottles, also helps to prolong their freshness and potency. For more information on the health benefits of cold-pressed oils, you can consult resources like the Cleveland Clinic's breakdown.

Conclusion: Choosing the Right Oil by Temperature

In conclusion, delicate, polyunsaturated-rich oils like flaxseed, walnut, and unrefined oils should be reserved for low- or no-heat applications. This helps to prevent harmful compounds from forming and retains the oil's nutritional value and flavor. For higher temperature cooking, select stable, high smoke point oils such as refined avocado, clarified butter (ghee), or refined coconut oil. Matching the oil choice with the cooking method is a simple way to improve both the safety and healthfulness of meals.

Frequently Asked Questions

The smoke point is the temperature at which an oil begins to break down and produce smoke. Cooking beyond this point can destroy nutrients and create toxic compounds.

Yes, cooking with smoking oil is unhealthy because it releases harmful free radicals and other toxic compounds. It can also give food a burnt, unpleasant taste.

Flaxseed oil cannot be heated because it contains high levels of omega-3 fatty acids (ALA) that are easily damaged by heat, light, and air. It should only be used for cold applications.

Extra virgin olive oil has a medium smoke point and is best for low-to-medium heat cooking, like sautéing or baking, but it is not ideal for high-heat frying. A refined olive oil is a better choice for higher temperatures.

For high-heat cooking, choose oils with high smoke points and high stability, such as refined avocado oil, clarified butter (ghee), and refined coconut oil.

Yes, reusing oil for frying is not recommended, especially polyunsaturated oils. Reheating can cause the oil to break down further and increase the concentration of toxic byproducts.

Delicate, low smoke point oils like flaxseed oil should be stored in a cool, dark place, preferably in the refrigerator, to prevent oxidation and rancidity.

Canola oil has a higher smoke point than some other oils, but it also has a high level of polyunsaturated fats, which are less stable at high heat. It's often used for cooking, but moderation and proper cooking temperatures are important.