Video | What are Seed Oils? | Concerns | Causation or Correlation | A Better Path Forward

Cooking fats come from different sources. Tallow, lard, and butter are derived from animals. Olive and avocado oil are pressed from those fruits, and seed oils are extracted from seeds.

Over the past few decades, we’ve seen an explosion in the use of vegetable-based seed oils as they have replaced the more traditional animal-based fats. 

How has that replacement worked out for us? This blog post shares facts and concerns surrounding seed oils so you can make decisions for yourself. 

The Skyrocketing Use of Seed Oils [Video]

In this video, you’ll learn…

• How seed oil use has increased overtime.
• Concerns associated with seed oils.
• tips to avoid using seed oils

What are Seed Oils?

Seed oils get their name because they are extracted from seeds. Commonly used seed oils include soybean, corn, cottonseed, safflower, sunflower, grapeseed, peanut, and canola or rapeseed oil.

Since the start of their commercial production around the early 1900s, vegetable-based seed oils have been on the rise (1).

As seed oil use increased, the use of animal-based fats decreased. A significant divergence in the use of added fats and oils occurred in the 1950s when Ancel Keys proposed the diet-heart hypothesis, suggesting that saturated fats, commonly found in animal products, cause heart disease. 

The use of seed oils increased even more after 1961 when the American Heart Association adopted Keys’ hypothesis, formally recommending that Americans decrease their consumption of saturated fats and replace them with polyunsaturated vegetable or seed oils (2).

We listened to that recommendation. Today, it is estimated that vegetable oils make up 8 to 10 percent of total energy intake in the Western world (3).

A note of clarity: The terms vegetable oil and seed oil are often used interchangeably. Technically, vegetable oil is a broad category that refers to oils extracted from various plant sources, including seeds, fruits, and other plant parts. Seed oils are a subset of vegetable oils derived specifically from the seeds of plants. 

Seed oils are sometimes referred to as omega-6 vegetable oils. Keep that term in mind because it will become part of our discussion in a moment. 

Seed Oil Concerns

Not everyone agrees that an increase in seed oil consumption is a problem. Proponents cite research showing that replacing saturated fats with polyunsaturated fats from seed oils can reduce LDL cholesterol levels. If cholesterol is a concern for you, I recommend reading my last blog post on Cholesterol and Keto, in which I discuss it in easy-to-understand language. 

Also, a defense argument for their use is that they are being wrongly blamed for poor health outcomes. The basis of this argument is that because seed oils are mass-produced and inexpensive, they are the oil of choice by fast food restaurants and packaged food companies. Since these fried and processed foods are known to be unhealthy for multiple reasons, you can’t put all of the blame on seed oils. 

In contrast, those who advocate against the widespread use of seed oils note that they are high in inflammatory omega-6 fatty acids, and the oil is hard to extract. Because of that, the oil must be pulled out using harmful chemicals or heat. 

Omega-6 to Omega-3 Imbalance

A major concern with the rising use of seed oils is that they are high in omega-6 fatty acids, particularly linoleic acid. Excessive linoleic acid can promote inflammatory pathways in the body.

You need some omega-6 fats for good health. In fact, they are essential nutrients, meaning your body can’t make them, so you must eat them. Omega-3 fatty acids are also essential nutrients. 

Before fried and processed foods were so common, most people got equal amounts of these fats. So, our ancestors consumed omega-6 and omega-3 fats in a ratio close to 1:1. Today, thanks to the Standard American Diet, the average person’s ratio is closer to 15:1. 

This imbalance creates a pro-inflammatory state within the body, increasing the risk of cardiovascular disease, obesity, diabetes, and other inflammatory conditions​.

Seed Oil Creation

How seed oils are extracted and processed is also a concern. As I mentioned, vegetable oils can be extracted from high-fat fruits like olives, avocados, and coconuts or from seeds. Because fruits are malleable, their oils can be extracted or pressed out without exposure to harmful chemicals or heat.

In comparison, seed oil is much harder to extract. Crushing the seeds releases some of the oil, but full extraction requires chemicals and heat. The crushed seeds are mixed with solvents, such as hexane, to dissolve the oil from the seeds. The oil is then separated, and the solvent is removed by heating. This process is efficient but can destroy nutrients and introduce harmful compounds. 

A couple of notes for clarity: First, the raw plant or seed does not have to be avoided. For instance, people eat edamame, which are immature soybeans, or raw sunflower seeds without the inflammatory consequences.

Also, sesame and flaxseed oil are considered less harmful seed oils due to their antioxidant levels and relative ease of extraction. However, they are still high in polyunsaturated fats, which makes them poor choices for high-heat cooking. 

Heating Seed Oils

What we’ve learned so far is that, right out of the gate, from their composition to their creation, seed oils present health concerns. These concerns are amplified when these polyunsaturated fats are used for cooking. 

Polyunsaturated fats contain multiple double bonds within their molecular structure. These double bonds make the molecule unstable and prone to oxidation when exposed to oxygen, light, or heat. 

What has been found is that when seed oils are heated, they can degrade and produce harmful compounds, such as trans fats and free radicals, which contribute to inflammation. High heat exposure can also generate toxic byproducts like aldehydes, which have been linked to various chronic diseases. 

And remember, because polyunsaturated seed oils are widely available and inexpensive, they are the oils used in deep fryers at fast food restaurants. These fryers subject the oil to repeated heating, generating even more toxic products (4). 

Are High-Oleic Seed Oils Better?

Before we leave the topic of cooking oils, you may come across the term “high-oleic” before certain oils (e.g., high-oleic sunflower oil, high-oleic safflower oil, high-oleic canola oil).

In general, these are better versions of the oils because they are more stable and less prone to oxidation when exposed to heat. That stability is due to the fact that they contain a high concentration of oleic acid (~70-85%), which is a monounsaturated fatty acid, and, therefore, a lower concentration of the unstable polyunsaturated fats. 

However, high-oleic oils are still highly refined, and although they are better cooking oils than traditional seed oils, an over-reliance on them may still contribute to an imbalanced intake of omega-6 to omega-3 fatty acids.  

Causation or Correlation? 

So here we are. We see that there are many studies linking high seed oil consumption with negative health outcomes, such as inflammation, cardiovascular disease, and obesity. However, these studies often observe dietary patterns as a whole. 

Seed oils are frequently used in processed and fried foods, which contain other harmful ingredients, making it difficult to separate the effects of seed oils from the overall unhealthy effects of poor food choices​. 

Are seed oils causing poor health outcomes, or is this simply a correlation? 

Here are some facts. Seed oil use has skyrocketed since the early 1960s. During the same timeframe, there has been a significant increase in average global life expectancy. 

However, the proportion of life spent in poor or moderate health has not changed. In other words, we are living longer but spending more years in poor health than at any point in history (5).

A Better Path Forward

Personally, I avoid seed oils. For me, the facts are clear that consuming high levels of them contributes to inflammation. Chronic inflammation can go undetected for decades, but when we peel back all the layers and look for the root cause of poor health, it is a top culprit, in my opinion. 

If you’d like to avoid seed oils, here are three things you can start doing today. 

(1) First, cook most of your meals at home. Cooking is a great skill to learn. You know what’s in your food, and it saves you money. 

(2) Second, when cooking, consider using extra virgin olive oil or avocado oil. High-quality brands of these monounsaturated oils are more stable when exposed to heat compared to the polyunsaturated fats found in seed oils. 

And, though more controversial, don’t discount cooking with saturated fats, like butter.

Because saturated fats have all single bonds within their molecular structure, they are the most stable fats for cooking.

(3) Third, eat whole foods. If it comes in a box, look at the ingredient list for the presence of a seed oil or the words “partially hydrogenated oil,” which is a process that alters the chemical structure of the polyunsaturated fats found in the oil, creating trans fats.

When you do those three things, you will reduce your exposure to toxic byproducts and naturally move toward yesteryear’s ideal 1:1 ratio of omega-6 to omega-3. And, to ensure you’re boosting omega-3s, include fatty fish, seafood, high-quality meats and dairy, raw nuts and seeds, and dark leafy greens in your diet. 

Thank you for reading and have a great week!

References:

(1) Lee, Joyce H., et al. “United States dietary trends since 1800: lack of association between saturated fatty acid consumption and non-communicable diseases.” Frontiers in Nutrition 8 (2022): 748847.

(2) Teicholz, Nina. “A short history of saturated fat: the making and unmaking of a scientific consensus.” Current Opinion in Endocrinology, Diabetes and Obesity 30.1 (2023): 65-71.

(3) DiNicolantonio, James J., and James H. O’Keefe. “Omega-6 vegetable oils as a driver of coronary heart disease: the oxidized linoleic acid hypothesis.” Open Heart 5.2 (2018): e000898.

(4) Leong, Xin-Fang. “Lipid oxidation products on inflammation-mediated hypertension and atherosclerosis: A mini review.” Frontiers in Nutrition 8 (2021): 717740.

(5) Coe, Erica, et al. “Adding years to life and life to years.” McKinsey Health Institute: Chicago, IL, USA (2022).

About the Author

Becky Gillaspy, DC, is the author of The Intermittent Fasting Guide and Cookbook and Zero Sugar / One Month. She graduated Summa Cum Laude with research honors from Palmer College of Chiropractic in 1991.