Seed oils are oils made from plant seeds. Home, restaurant, and food preparation facilities commonly use seed oils because of their versatility, high smoke point, and neutral flavor.
Seed oils have become controversial due to their high omega-6 content. While research shows that omega-6 fatty acids are beneficial, particularly concerning heart health, concerns have arisen around the role of omega-6 fatty acids in inflammatory processes.
Are Seed Oils Bad for You?
No, seed oils are not inherently bad for you unless you are allergic to them. Seed oils contain a mix of anti-inflammatory mono- and polyunsaturated fats and plant compounds with beneficial health properties. Here is more information about their safety.
People allergic to seed oils or their components should avoid them. Individuals with nut allergies should avoid any seed oils derived from nuts, such as peanut oil. If you have a sesame allergy, do not consume sesame oil. Although rare, allergic reactions to soybean and sunflower oil have been reported.
The seed oil you use likely came from a genetically modified organism (GMO) crop. Corn, canola, cotton, and soybeans are among the most common GMO crops. The Food and Drug Administration (FDA) deems these items safe for consumption. GMO crops are modified to resist pests, potentially reducing the need for specific pesticides and insecticides. Humans have been effectively genetically modifying crops for centuries, albeit more slowly, to create the most robust plants via selective breeding. However, there are concerns with GMOs about the loss of plant biodiversity, genetic material from GMOs being transferred to other plants, and the use of specific herbicides.
Debate on the safety of seed oils stems from their omega-6 content. Your body converts linoleic acid—the dominant omega-6 fatty acid in seed oils—into another omega-6 called arachidonic acid. In turn, arachidonic acid gets converted to either proinflammatory or anti-inflammatory molecules.
Opponents of seed oils believe that consuming foods high in omega-6s increases inflammation in the body. However, research does not support this. Studies reporting adverse effects of seed oils were suboptimally designed. Additionally, eating foods rich in linoleic acid does not appear to increase levels of arachidonic acid or affect inflammation.
Opponents of seed oils also note the balance between omega-6 and omega-3 fatty acids. Omega-6 and omega-3 fatty acids compete for the same metabolism enzyme, potentially impacting the production of anti-inflammatory molecules. However, research in this area is complex and yields conflicting results.
The issue may lie with a diet’s lack of omega-3 fatty acids. Rather than worrying about cutting back on specific omega-6-rich oils, researchers propose increasing your consumption of omega-3s. Fatty fish are a significant source of omega-3 fatty acids, and most Americans do not meet the recommended two servings weekly to achieve sufficient omega-3 levels.
The fat profile of seed oils suggests they have no impact on inflammation. However, seed oils are common in fast food, restaurant meals, and packaged or ready-made food items. Due to their high smoke point, seed oils are often used for frying. Repeatedly frying foods in the same oil increases the development of harmful molecules associated with inflammation and chronic diseases.
Other packaged, highly processed foods made with heated oil may also contain molecules associated with an increased risk of heart disease. Reducing fried food consumption may be better than eliminating seed oils from cooking altogether.
What Are Seed Oils?
Seed oils are oils derived from the seeds of plants. Seed oils can come from the seeds of vegetable, herb, and fruit plants.
Some seed oils are commonly referred to as the “hateful 8.” Members of this group include the following:
However, other oils are also considered seed oils because they come from plant seeds, such as the following:
Seed oils are used in cooking to flavor foods, create texture, prevent sticking in pans, and allow for higher cooking temperatures and even heat distribution. They can be added during the cooking process or immediately before serving for additional flavor, garnish, or as a dressing.
Nutritional Profile of Seed Oils
Seed oils are nearly 100% fat. Unlike butter and tropical oils, seed oils have a low saturated fat content and are packed with unsaturated fats.
Seed oils contain a mix of mono- and polyunsaturated fatty acids. Omega-3 and omega-6 fatty acids are essential polyunsaturated fats associated with health benefits. Omega-6s are the predominant fatty acid in most seed oils. Specifically, seed oils are a potent source of the omega-6 fatty acid linoleic acid.
Seed oils contain fat-soluble vitamins (vitamins that need fat for absorption), like vitamin E and vitamin K. They also contain plant compounds associated with health benefits (polyphenols). Moreover, seed oils are a significant source of phytosterols, plant compounds that are structurally similar to cholesterol and benefit blood cholesterol levels. Refining alters the nutrient composition, reducing vitamin E, polyphenol, and phytosterol content.
| Seed Oil Fat Profile | |||||
|---|---|---|---|---|---|
| Saturated fat | Monounsaturated fat | Polyunsaturated fat (total) | Omega-6 | Omega-3 | |
| Canola oil | 7% | 66% | 27% | 19% | 8% |
| Safflower oil | 8% | 77% | 15% | 14.5% | Less than 1% |
| Grapeseed oil | 9% | 16% | 70% | 69% | Less than 1% |
| Flaxseed oil | 9% | 18% | 68% | 14% | 53% |
| Sunflower oil | 9.5% | 68% | 22% | 22% | Less than 1% |
| Sesame oil | 14% | 40% | 42% | 42% | Less than 1% |
| Soybean oil | 16% | 23% | 61% | 54% | 7% |
| Peanut oil | 17% | 61% | 21% | 21% | Less than 1% |
| Rice bran oil | 20% | 39% | 35% | 35% | Less than 1% |
| Corn oil | 21% | 29% | 56% | 56% | Less than 1% |
Health Benefits of Seed Oils
The health benefits of seed oils are due to their nutrition profile, namely their fatty acid composition, and include:
- Heart Health: Reducing saturated fat and replacing it with polyunsaturated fats lowers the risk of heart disease. Replacing saturated fat with linoleic acid, a majority of polyunsaturated fats in seed oils, reduces low-density lipoprotein (LDL) cholesterol (considered “bad” cholesterol). Consuming linoleic acid decreases risk factors for heart disease, including total cholesterol and triglycerides.
- Anti-Inflammatory Effects: Mono- and polyunsaturated fats are associated with anti-inflammatory benefits. Research shows that incorporating omega-6 linoleic acid into the diet does not necessarily increase inflammation. Studies demonstrate that omega-6s have little to no effect on inflammatory markers.
- Weight Management: Seed oils’ fatty acid composition may contribute to their beneficial effects on weight management. Omega-3 fatty acids help regulate signals for fat accumulation and energy metabolism, whereas omega-6s may influence the breakdown of stored fat. One large analysis found that canola and sesame oil contributed to weight loss.
- Blood Sugar: Polyphenols may support carbohydrate (glucose) metabolism and reduce insulin resistance, a primary characteristic of type 2 diabetes. However, the benefit of seed oils on blood sugar may be specific to the oil. Flaxseed oil affects insulin sensitivity and reduces inflammation, which helps manage and treat diabetes. Other research shows that sesame oil reduces hemoglobin A1c and fasting blood sugar.
- Antioxidant Effects: Seed oils are packed with tocopherols, compounds comprising or resembling vitamin E. Tocopherols have antioxidant effects, helping to reduce oxidative stress, which contributes to chronic diseases. Other compounds in seed oils, like polyphenols and phytosterols, also reduce free radicals to prevent cell damage.
- Skin Health: Seed oils’ polyphenol and fatty acid composition may support skin health when applied topically (on the skin). Topical application of seed oils strengthens fatty acids naturally present in the skin and may help moisturize skin and reduce cell damage.
- Brain Function: Omega-3 fatty acids like docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are essential for cognitive function. Higher levels of DHA and EPA are associated with improved cognition later in life. Arachidonic acid from omega-6 fatty acids also supports brain development and cognitive function.
- Immune Function: Omega-6 fatty acids influence immune function involved in inflammatory responses. They help strengthen immune cell membranes. Other compounds in seed oils, like phytosterols, boost immune function.
How Are Seed Oils Made?
The production of seed oils involves various methods, each tailored to the type of seed and the desired quality of the oil. Factors such as cost, efficiency, and the intended use of the oil play a significant role in determining which extraction and refining processes to use.
Extraction Methods
Cold-pressed extraction is done under low temperatures and does not require any chemicals. Because of this, cold-pressed oils contain more phytochemicals and antioxidants.
Chemical extraction is more extreme than cold-pressing. Chemical extraction uses substances that dissolve in liquid (solvents) and high temperatures to extract the oil from its seed.
The Refining Process
Oils like soybean, corn, and sunflower must be refined before consumption. Refining removes unwanted compounds to create a neutral taste. It also reduces the potential for changes to the oil when it comes into contact with oxygen (oxidation). Refining makes the oils more stable for shipping, storage, and use.
Two popular refining methods are chemical and physical refining. Both involve “bleaching” to remove color pigments and “deodorizing” to eliminate dangerous and unstable compounds.
Other Considerations
Cold-pressing is safe, energy-efficient, and environmentally friendly. However, it produces less oil than other techniques. Cold-pressing is a physical refining technique. Physical refining is typically more economical and environmentally friendly than chemical refining, but it is not recommended for all oil types.
The methods of extracting and refining seed oils vary based on factors like seed type, cost, and desired oil quality. Cold pressing may offer a more natural, nutrient-rich option, but chemical and physical refining processes tend to focus on efficiency, stability, and a longer shelf life.
Choosing the Right Seed Oil
Many factors must be considered when choosing the right seed oil. First and foremost, consider your oil’s intended use.
Reading the Label
No strict rule exists for purchasing seed oils. Instead, think of the oil’s intended use. If you’re drizzling oil on top of a salad or using it as a garnish or fish, go with a cold-pressed oil. Cold-pressed and extra virgin oils retain more of their polyphenol content.
Seed oils produced from GMO crops cannot be organic. However, you may be able to find organic seed oils from more specialized seeds like pumpkin or walnut.
Storing Your Oil
Storage temperature, light, and heat affect seed oils and contribute to oxidation. Store seed oils in an opaque container (one that’s dark and not able to see through it) container in a cool, dark place, and do not hold onto them for longer than four months.
Shelf Life
Most oils last for a few months. Purchase smaller oil containers if you don’t think you’ll go through it within a few months. Do not use oils that smell bad. Oils stored for too long can become oxidized and spoil. Do not reuse or reheat cooking oil, as this can contribute to consuming harmful molecules.
Taste and Flavor
Most seed oils have a fairly neutral taste. However, sesame oil tastes more pungent, and flaxseed oil may be bitter. If you’re using seed oil for sauteing or baking, opt for the more neutral flavor of canola, grapeseed, corn, soybean, safflower, or sunflower. Sesame oil can be an excellent pick for adding a nuttier flavor to a dish or dressing. Balance the bitterness of flaxseed oil with sweetness when creating a dressing.
Allergies and Sensitivities
Seed oils generally are considered safe for most people to consume. However, people with nut allergies should avoid peanut oil or other oils derived from tree nuts. If you have a sesame allergy, avoid sesame oil.
Health Goals
Choosing seed oils over tropical oils or butter confers many health benefits, such as boosting heart health and reducing inflammation. Research shows that replacing 5% of calories from saturated fat with the same caloric intake from polyunsaturated fats is associated with a 25% lower risk of heart disease.
If your diet is low in omega-3-rich foods, consider choosing a seed oil with a more optimal mix of omega-3s and omega-6s, such as flaxseed or canola oil.
Nutrient Profile
Remember that all oils are a significant source of fat. The Dietary Guidelines of America recommends that 20 to 35% of your daily calories come from fats. On a 2,000-calorie-a-day diet, 30% of calories from fat equates to roughly five tablespoons of oil. So, regardless of oil type or benefits, it remains essential to be mindful of how much oil you use.
Smoke Point
Seed oils’ high smoke points allow you to try different cooking techniques with less worry about ingesting harmful compounds from burned oil. The smoke point reflects when an oil begins burning during cooking. It takes longer for high smoke point oils to oxidize during cooking, meaning you can apply heat to your food for more time. Seed oil smoke points vary depending on the type of oil and the extraction and processing methods.
How You Cook
You may want one oil over another depending on what you are cooking. Refined oils generally have a higher smoke point than their unrefined counterparts. Frying, stir-frying, or broiling requires a high smoke point oil like soybean, safflower, or corn, which works well at about 450 degrees F.
Use an unrefined seed oil for low-heat cooking between 300 and 350 degrees F. Flaxseed or almond oils are best suited for settings that don’t require cooking, such as with garnishes or salad dressings.
Summary
Cooking with seed oils in your home confers little health risk. In fact, the nutrition profile of seed oils is associated with health benefits, including reduced inflammatory markers and a lower risk of heart disease.
Harmful molecules are rarely created from home cooking; oils seldom reach their smoke point for long periods. Rather than eliminating seed oils from your diet, consider reducing your intake of fried or packaged foods that may be doing more harm than the oils themselves.
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