Understanding Seed Oils and Cooking Fats

Seed oils are some of the most commonly used cooking fats, however they're often discussed without much context. They frequently appear in home kitchens, restaurants, and packaged foods. This has caused them to be a central topic in many nutrition conversations Understanding what they are and why they're used helps explain why opinions about them vary so widely.

So what exactly are seed oils? Seed oils are oils extracted from the seeds of plants rather than from fruits or animal sources. Some of the most commonly used seed oils are sunflower oil, canola oil, and corn oil just to name a few. These oils are widely used in home kitchens, restaurants, and pre-packaged foods. Seed oils are often used because they are so inexpensive to produce. Additionally, seed oils are also able to withstand high heat and have a long shelf life, making them quite convenient for frying and packaged foods. Seed oils have a neutral flavor which allows them to blend easily into a wide range of recipes without altering their taste.

Despite their convenience for your wallet and its widespread uses, seed oils have become a topic of debate in nutrition circles, with concerns often centered around how they are processed and how they affect long term health. Seed oils undergo significant processing. Eric Decker, a professor emeritus  of food science and lipids researcher at the University of Massachusetts Amherst, explains this process involves the use of high heat, chemical solvents (like hexane), bleaching, and deodorizing to achieve the oil's final appearance. Decker also mentions that the hexane and other chemical solvents are removed in processing, but small amounts end up in the final product, but they are "toxicologically insignificant." These chemical solvents are evoprated once heated during cooking.

So why are they so bad for you? The concern about seed oils does not come from them being inherently toxic, rather it's about how they are commonly consumed in modern diets. Seed oils are high in omega-6 fatty acids and low in omega-3s. The general rule of thumb when consuming omega-6s and omega-3s is to consume them in a 1:1 or 4:1 ratio. The omega-6 to omega-3 ratio in most seed oils is 70:1, this imbalance promotes inflammation by influencing inflammatory signaling pathways, especially when seed oils are consumed through highly processed and fried foods. Tom Brenna, a researcher at the University of Texas at Austin has spent decades studying fatty acids and is concerned that some people are consuming too many omega-6s in their diet as not everyone processes omega-6s the same way. He states that emerging research suggests some individuals may be more susceptible to inflammation associated with omega-6 fatty acids. This can cause chronic inflammation which can lead to autoimmune diseases such as Rheumatoid Arthritis and Lupus. Additionally, because many seed oils are rich in polyunsaturated fats, they can be more prone to oxidation when exposed to high heat, potentially forming harmful byproducts. For this reason, the consumption of seed oils is often recommended to be moderated.

There are many alternatives which provide many health benefits as well. Two famous cooking fats which have made a huge comeback in recent years are ghee and beef tallow. Ghee contains fat-soluble vitamins like vitamins A, E, and K, and also provides butyrate, a short-chain fatty acid that supports gut health and aids in reducing inflammation. Due to the milk solids being removed, ghee is also better tolerated by individuals sensitive to lactose. Beef tallow is rich in saturated and monosaturated fats, which makes it highly stable at high temperatures and resistant to oxidation. It also contains small amounts of naturally occurring vitamins such as vitamin D and conjugated linoleic acid (CLA). CLA can aid in reducing body mass, help preserve lean muscle, reduces fat storage in fat cells and slightly increasing the use of fat for energy, and CLA can also help modulate inflammation. When used in moderation, both fats can be useful options for high-heat cooking while contributing to overall dietary fat intake. 

Beef tallow and ghee are great alternatives, but they may not be for everyone. Olive and avocado oil are two great alternatives and are vegan/vegetarian friendly. Olive oil is widely valued for its high monounsaturated fat content and the presence of naturally occurring polyphenols, which act as antioxidants and support heart health. Regular consumption of olive oil has been associated with improved cholesterol profiles and reduced markers of inflammation, particularly when used within whole-food dietary patters. Avocado oil offer similar benefits, providing monounsaturated fats that support cardiovascular health along with vitamin E, and antioxidant that helps protect cells from oxidative stress. Its higher smoke point and neutral flavor make it especially versatile for both cooking and food preparation. Together, olive oil and avocado oil are commonly chose for everyday use due to their balance of stability, nutrient content, and minimal processing. 

Seed oils are not inherently harmful and do provide essential fatty acids. Concerns mainly arise when they re consumed in excess through heavily processed foods. For everyday cooking, many people choose fats like olive oil, avocado oil, or ghee based on their multiple health benefits and stability. However it's true that these cooking fats are often more expensive than seed oils so not everyone may be able to afford them. If you choose to cook with seed oils, focus on moderation as the overall diet matters more than one specific fat.

References:

Seed Oils, Science, Controversy. 

Seed Oils and Healthier Alternatives.