A Nutrition Guide to Which Oils Are Polyunsaturated Fat?

November 1, 2025 •

4 min read

According to the American Heart Association, replacing saturated fats with polyunsaturated fats (PUFAs) can help lower bad cholesterol levels, reducing the risk of heart disease. But a question many people have is, "Which oils are polyunsaturated fat?" and how can they be used to support a healthier diet.

Quick Summary

This article identifies common oils rich in polyunsaturated fats, breaks down the essential omega-3 and omega-6 fatty acids they contain, and explains their benefits for heart and brain health. It also provides guidance on cooking applications and balancing intake for optimal nutrition.

Key Points

Key Oils: High polyunsaturated fat oils include sunflower, corn, soybean, flaxseed, and safflower, primarily from plant and seed sources.
Omega Balance: Polyunsaturated fats are divided into omega-3 and omega-6, both essential for health, but modern diets often contain an unbalanced ratio.
Low Heat Cooking: Because they are less heat-stable, polyunsaturated oils are best used for low-temperature cooking, dressings, and marinades to prevent oxidation.
Heart Health: Replacing saturated fats with polyunsaturated fats can help lower LDL ('bad') cholesterol, supporting cardiovascular health.
Essential Nutrients: The body cannot produce essential omega-3 and omega-6 fatty acids, meaning they must be obtained through a balanced diet.
Whole Food Sources: Incorporate more polyunsaturated fats by eating whole foods like fatty fish, walnuts, flaxseeds, and soybeans.

What Are Polyunsaturated Fats?

Polyunsaturated fats are a type of unsaturated fat, alongside monounsaturated fats. While saturated fats are solid at room temperature, PUFAs are typically liquid. Their defining feature at a chemical level is the presence of more than one double bond in their carbon chain, which makes them less stable when exposed to heat compared to saturated fats. There are two primary types of polyunsaturated fats: omega-3 and omega-6 fatty acids. Both are considered "essential" fats because the human body cannot produce them and must obtain them from food. Incorporating a healthy balance of these fats into your diet is crucial for supporting cell growth, brain function, and overall heart health.

Which Oils Are Rich in Polyunsaturated Fats?

Several vegetable and plant-based oils are excellent sources of polyunsaturated fats, with varying ratios of omega-3 and omega-6 fatty acids. The following oils are particularly well-known for their high PUFA content:

Safflower oil: Extremely high in omega-6 PUFAs.
Sunflower oil: A very good source of omega-6, and can come in different varieties (e.g., high-oleic, mid-oleic) that affect its overall composition.
Flaxseed oil: Provides a significant amount of omega-3 PUFAs, specifically alpha-linolenic acid (ALA).
Corn oil: Another common vegetable oil with a high omega-6 content.
Soybean oil: Widely used and contains both omega-6 and ALA omega-3 fatty acids.
Walnut oil: A flavorful oil that offers a good mix of both omega-3 and omega-6.
Grapeseed oil: High in omega-6 PUFAs.

Omega-3 vs. Omega-6: Balancing the Essential Fats

Polyunsaturated fats are comprised of two key families: omega-3 and omega-6 fatty acids. While both are essential, their functions in the body differ, and maintaining a healthy balance is critical. Historically, human diets contained a roughly balanced ratio of omega-6 to omega-3. However, modern Western diets are often skewed, with excessive omega-6 intake and insufficient omega-3, which can contribute to chronic inflammation.

Omega-3 Fatty Acids: These have anti-inflammatory effects and are associated with a reduced risk of heart disease. The most beneficial types, EPA and DHA, are found mainly in fatty fish like salmon, mackerel, and sardines. Plant-based sources contain ALA, which the body can convert to EPA and DHA, though inefficiently. Good plant sources include flaxseed oil, walnuts, and chia seeds.
Omega-6 Fatty Acids: Primarily sourced from vegetable oils like corn, soybean, and sunflower oil, omega-6s are important for energy and immune function. While essential, excessive amounts can promote inflammation, so it's wise to be mindful of intake from refined oils.

Cooking with Polyunsaturated Oils

Due to their chemical structure, polyunsaturated fats are more susceptible to oxidation and degradation when exposed to high heat. When oils are heated past their smoke point, they produce harmful compounds and free radicals, which can be damaging to health. Therefore, not all polyunsaturated oils are suitable for high-temperature cooking methods like deep-frying. For high-heat applications, oils with a higher percentage of saturated or monounsaturated fats are more stable.

Best for Low-Heat Cooking & Dressings: Flaxseed oil and walnut oil, rich in delicate omega-3s, should be used for cold applications like salad dressings or drizzled over finished dishes. Some refined oils like sunflower or soybean oil are more stable and can be used for light sautéing, but still aren't ideal for prolonged, high-heat cooking.
Best for High-Heat Cooking: When frying or roasting at high temperatures, consider using oils that are higher in monounsaturated fats (like olive or canola oil) or saturated fats (like coconut oil or animal fats), as they are more heat-stable.

Polyunsaturated vs. Other Oil Types

To make informed choices, it's helpful to understand how different types of cooking oils compare in their fatty acid composition and ideal usage.


Oil Type	Predominant Fat	Fatty Acid Profile	Best Use	Heat Stability	Example	Citations
Polyunsaturated	Omega-3, Omega-6	Multiple double bonds	Low-heat cooking, dressings	Low	Flaxseed Oil, Corn Oil
Monounsaturated	Omega-9	One double bond	Medium to high-heat cooking	Medium	Olive Oil, Canola Oil
Saturated	Saturated Fat	No double bonds	High-heat cooking, baking	High	Coconut Oil, Butter

How to Incorporate Healthy Polyunsaturated Fats Into Your Diet

There are many ways to increase your intake of beneficial polyunsaturated fats, especially omega-3s, while balancing your overall fat consumption. Here are some practical tips:

Choose the Right Oil for the Job: Use flaxseed or walnut oil in dressings and marinades, and opt for a more heat-stable oil like olive or avocado oil for sautéing and roasting.
Eat More Fatty Fish: Include fatty fish like salmon, mackerel, and sardines in your meals at least twice a week to get a direct source of EPA and DHA omega-3s.
Use Nuts and Seeds: Sprinkle walnuts, flaxseeds, or sunflower seeds on salads, yogurt, or oatmeal for an easy PUFA boost.
Create Your Own Salad Dressing: Ditch store-bought dressings that may contain excessive omega-6-rich oils. Instead, make your own with a base of flaxseed oil and a touch of olive oil.
Swap Animal Protein for Plant Sources: Replace some red meat with tofu or soybeans, which are also sources of polyunsaturated fat.

Conclusion: Making Informed Choices

Knowing which oils are polyunsaturated fat is the first step toward optimizing your fat intake for better health. These essential fats, vital for brain function, cellular health, and reducing heart disease risk, are readily available in a variety of oils and whole foods. By choosing a balanced mix of sources, being mindful of cooking temperatures, and emphasizing omega-3s while moderating omega-6s, you can ensure your diet is supporting your body's needs. Making small, informed changes, like swapping saturated fats for healthier alternatives in your cooking, can have a significant and lasting impact on your overall well-being. For more detailed information on healthy eating patterns, visit the American Heart Association's guide to healthy cooking oils.

Reference: Heart Foundation, "Choosing cooking oils" - https://www.heartfoundation.org.nz/about-us/news/blogs/choosing-cooking-oils

Frequently Asked Questions

The main difference is their chemical structure. Polyunsaturated fats have more than one double bond in their carbon chain, while monounsaturated fats have only one. Both are considered healthy fats, but their stability at different temperatures can vary.

Omega-3 and omega-6 fatty acids are both types of polyunsaturated fats and are essential for the body. Omega-3s, found in fatty fish and flaxseed, are generally anti-inflammatory. Omega-6s, common in many vegetable oils, can be pro-inflammatory in excess, so balancing the intake is important.

High heat can cause polyunsaturated oils to oxidize and break down, creating harmful compounds and free radicals that can negatively impact health. This is due to their chemical instability caused by multiple double bonds.

No. While many common vegetable oils like corn and sunflower oil are high in polyunsaturated fats, other vegetable oils, such as olive oil and canola oil, are higher in monounsaturated fat. Tropical oils like coconut and palm oil are high in saturated fat.

While the ideal ratio is debated, experts suggest aiming for a ratio of between 1:1 and 4:1. The typical Western diet often has a much higher ratio, with many consuming too much omega-6 and not enough omega-3.

Excellent plant-based sources of omega-3s (in the form of ALA) include flaxseed oil, walnuts, and chia seeds. While conversion to the more beneficial EPA and DHA is inefficient, consuming these foods regularly can help increase intake.

Yes, all fats, regardless of whether they are saturated or unsaturated, provide 9 calories per gram. This is more than twice the calories found in carbohydrates or protein, so moderation is key.