Seed Oils: Separating Fact From Fiction, Part 1

Recently, I’ve been getting lots of questions about seed oils. Promoted as the latest “food villains” — they seem to be dominating headlines. But, are they really all that bad for us? The answer isn’t as straightforward as you might think and the data is far more nuanced than what the headlines may have you believe. Welcome to another multi-part series that delves into a complex health topic in more depth.

In this week’s installment, I will go over seed oil nutrition basics for some level setting. In the two subsequent blogs I will cover seed oil myths and concerns, and where seed oils fit within a healthy dietary pattern.

What oils are considered seed oils? 

Seed oils, often referred to as vegetable oils, are oils extracted from the seeds of plants. They are widely used in cooking applications because they have a high smoke point, meaning they are stable at high temperatures. Many of the oils are also inexpensive to produce, making them an attractive option for manufacturers of various dressings, fast foods and snacks, as well as mass-produced baked goods. As a result, they are ubiquitous in our food supply.

Examples of seed oils include canola oil, corn oil, soybean oil, grapeseed oil, cottonseed oil, sunflower oil, safflower oil, and rice bran oil. Although sesame oil, peanut oil, and flaxseed oil are also seed oils, they are typically not singled out when seed oils come up in discussion.

What oils are not considered seed oils? 

Olive oil and avocado oil are not seed oils because they are extracted from the flesh of the olive and avocado fruits, respectively. And even though nut oils, such as almond and walnut oil are derived from extracting the fats from almond and walnut seeds, these are also not considered seed oils because nuts are botanically classified as fruits with a hard woody shell.  

What makes seed oils nutritionally interesting? 

Nutritionally, seed oils deliver plant-based polyunsaturated fats (PUFAs), including both alpha linolenic acid (ALA, an omega-3 fatty acid) and linoleic acid (LA, an omega-6 fatty acid). ALA and LA are considered essential fatty acids, meaning our bodies can’t produce them on their own so we have to get them from our food supply. And seed oils are a concentrated source.  Omega-3s are known for their anti-inflammatory properties and heart health benefits while omega-6s play a role in brain development and muscle growth.  

For optimal health, we require approximately 15 grams of LA and 2 grams of ALA per day (this is why two daily servings of Step One Foods provides 2 grams of ALA omega-3s).  In addition, PUFAs should be consumed in such a way as to attain a 4:1 ratio (or less) of omega-6 to omega-3 intake as based on total intake of these fatty acids (both essential and non-essential, including EPA, DHA, etc.).

Why the nutritional concern? 

Seed oils are far richer in LA than ALA, with soybean oil, for example, supplying 10 times as much LA compared to ALA per serving. Given how ubiquitous seed oils are, it becomes really easy to exceed optimal LA amounts - and really hard to ever reach an optimal omega 6 to omega 3 ratio. 

The standard American diet is characterized by a high intake of seed oils (40 grams per day, accounting for 20-30% of total calories), resulting in a highly imbalanced omega 6 to omega 3 ratio of approximately 20:1 in favor of omega-6. 

So should we be worried? And is there even more to this story?

In the next installment I will examine why seed oils are getting such a bad rap and put those concerns in context.