Are Seed Oils Bad for You—or Actually Healthy?

Medically reviewed by Maggie Moon, MS, RD

• Seed oils in moderation may help lower cholesterol, protect heart health, and provide antioxidant benefits.

• Research suggests that omega-6 fats in seed oils do not significantly increase inflammation or disease risk.

• Seed oils are safe for cooking when used properly, but avoid reusing them and store in cool, dark places.

Seed oils, sometimes called vegetable oils, have a controversial reputation. Some think they increase inflammation, weakening the immune system and increasing disease risk.

Are Seed Oils Unhealthy?

Seed oils are not inherently unhealthy and may have health benefits when consumed in moderation.

Seed oils include:

• Canola (rapeseed) oil

• Grapeseed oil

• Peanut oil

• Soybean oil

• Sesame oil

• Sunflower oil

• Safflower oil

• Cottonseed oil

A key criticism is their unsaturated fat content, which may contribute to inflammation and heart issues.

Critics highlight the processing of seed oils, involving extraction and refining to remove unwanted compounds.

Solvent chemicals like hexane, derived from crude oil, help extract the oil. Some worry about its levels in commercial seed oils.

Deodorization lightens color and removes odor but may increase trans fats content, a harmful dietary fat.

Limited research supports these criticisms; most studies find health benefits outweigh risks.

Health Concerns of Seed Oils

Health concerns involve oil composition, manufacturing, and use in processed foods.

1. Inflammation

Seed oils may have high omega-6, specifically linoleic acid, which you can only get through diet.

Linoleic acid is a precursor to arachidonic acid, which may increase inflammation and raise the risk of diseases like asthma, heart disease, and cancer.

A meta-analysis found that omega-6 levels do not significantly impact inflammation; only small amounts of linoleic acid convert to arachidonic acid.

2. Cardiovascular Diseases

In a 2019 analysis of 30 studies, researchers found that higher levels of linoleic acid in a person’s diet lowered their chances of cardiovascular diseases, stroke, and death. Seed oils contain omega-3 and oleic acid, which support heart and blood vessel health.

3. Health Effects of Processing

Some deodorized oils contain small amounts of trans fats, and frying or cooking with seed oils can raise levels. However, seed oils generally aren’t a significant source of trans fat.

Another concern relates to the use of hexane in extracting seed oils. But in commercially available seed oils, there’s little to no hexane. The levels are too low to be dangerous.

4. Seed Oils and Ultra-Processed Foods

Seed oils like canola and sunflower are common in processed and ultra-processed foods like chips, fast food, or frozen meals. Regular over-consumption of these foods can lead to a range of conditions, including obesity, diabetes, cardiovascular diseases, and others.

That said, the negative impacts on health associated with these foods are more likely caused by other ingredients—such as excess salt, added sugar, and high-fructose corn syrup—and the replacement of some fruits and vegetables with these foods.

Health Benefits of Seed Oils

There’s a great deal of evidence that seed oils—when used in moderation—offer many health benefits. These include:

1. Better Control of Cholesterol

Seed oils are rich in unsaturated fats. These help with essential body functions and break down low-density lipoprotein (LDL, or “bad”) cholesterol.

2. Lowered Risk of Cardiovascular Disease

Studies have linked the unsaturated fats in seed oils to reduced risk of heart disease, stroke, and other cardiovascular diseases.

3. Antioxidant Properties

Seed oils are rich sources of the antioxidant vitamin E. These help prevent oxidation, chemical reactions that produce free radicals (substances that damage cells and contribute to chronic disease).

4. Improved Blood Sugar Control

Seed oils may also boost sugar metabolism by reducing insulin resistance. Some research found that replacing carbohydrates and saturated fat with unsaturated fat in canola oil can help control blood sugar in people with diabetes or prediabetes.

Tips and Considerations

Unsaturated fats like those found in seed oils are an essential part of a healthy, balanced diet. If you’d like to incorporate them, here’s what to keep in mind:

• Moderation: Using a few tablespoons of seed oil to cook with or on salad isn’t risky. Seed oils are high in calories, so the key is to use them in moderation.

• Smoke point: The smoke point is the temperature at which an oil burns. It’s high for canola, avocado, and peanut oil, making them good options for high-heat cooking. Other seed oils are better for low-heat cooking or salad dressings.

• Single use: If you reuse seed oils, it can increase the trans fat and saturated fat content. Discard leftover oil after cooking or deep frying.

• Storage: Store seed oil bottles at room temperature, sealed tightly, and in a pantry or dark place. Use them within 6-12 months of purchase, and three months after opening.

• Safety: Seed oils are safe for most people. Those who are allergic to seeds like peanuts or sesame should avoid those oils, which can trigger attacks.

Next Steps

• Use seed oils, such as canola or corn oil, with a low omega-6-to-omega-3 ratio for cooking.

• Store seed oils in cool, dark places to maintain their quality.

• Limit your intake of ultra-processed foods containing seed oils to support your overall health.

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