The Truth About Seed Oils Most People Don't Want to Hear
Nutrition is a nuanced subject, similar to other topics that cause controversy. As much as we want to draw a line in the sand to separate good and bad, most things just don't work that way.
Despite this, people like to demonize specific food items. Unfortunately, this often comes from people on social media platforms with large audiences who don't understand the nuances of nutrition and just want to make headlines. Worse yet, they may have an agenda with the end goal of selling a book or a coaching program.
Seed oils may take top billing as the most demonized food ingredient out there right now. Just seeing the words seed oils has a negative connotation. But are they truly deserving of this distinction?
What Are Seed Oils?
Seed oils are vegetable oils made… from seeds. Examples include canola, corn, cottonseed, grapeseed, rice bran, safflower, soybean, and sunflower. These oils are referred to at times as the hateful eight. They are typically made using heat and chemical solvents like hexane (we'll get to that later) to extract the oil, but can also be cold-pressed.
Conflating Seed Oils with Unhealthy Foods
Before we get into the research on seed oils, it's important to understand the distinction between seed oils and the foods that they are commonly found in.
Seed oils are cheap to produce, shelf stable, and have a neutral taste. This is why so many food manufacturers use them.
The problem is that they end up in your typical junk foods like chips, cookies, frozen pizza, and fast food. As a result, people believe it is the seed oils doing the harm rather than the combination of high calories, saturated fat, sugar, and sodium, along with the lack of vitamins, minerals, and fiber.
To truly understand if seed oils are the culprit for all of our health problems, we need to look at research on seed oils by themselves. That way it removes the other variables to create a clearer picture.
What the Studies Show When Seed Oils Are Isolated
One of the main talking points about seed oils is about inflammation, due to the high omega-6 fatty acid content. Omega-6 and omega-3 are the two main polyunsaturated fats consumed in the diet. You may be familiar with the health benefits of omega-3 fatty acids, notably its anti-inflammatory properties. You may even take an omega-3 fish oil supplement.
However, this has led to the misconception that omega-6 fatty acids are inflammatory simply because they are not omega-3s. People assume that the two are polar opposites, which they are not.
In a recent interview, Stanford's Christopher Gardner, PhD and Director of Nutrition Studies, explains that omega-6s are also anti-inflammatory, just not to the same degree as omega-3s.
A separate meta-analysis by Marklund et al. found that higher levels of linoleic acid in the blood were associated with a 35% lower risk of developing type-2 diabetes. It is hypothesized that this is due to linoleic acid's positive effect on glucose metabolism.
Manufacturing Concerns of Seed Oils
A common anti-seed-oil argument is that the manufacturing process (which involves a solvent called hexane) makes them toxic. Research confirms that hexane is efficiently evaporated and recovered from the oil upon heating. The deodorization process also reduces environmental contaminants while also maintaining vitamin E levels.
Analyses of oils in the marketplace confirm a typical U.S. consumer would have to consume more than 100 times more oil each day than current averages to reach even the lowest safety limit for hexane.
Toxic is a word thrown around often in nutrition circles. But everything is toxic at a certain level: water, vitamins, even oxygen. It's easy to scare someone by using the word toxic to describe something they are consuming, but as the saying goes: the damage is in the dose.
Narrative Review Against Seed Oils
A narrative review by pharmacist James DiNicolantonio and cardiologist James O'Keefe, published in BMJ Open Heart, is one of the most frequently cited pieces in the anti-seed-oil community. On the surface, it reads as a compelling indictment of seed oils, and the sheer volume of references gives it an air of authority.
However, it's important to note that a narrative review is not a study itself. The studies cited are hand-picked, with no methodology behind their selection. This creates the potential for confirmation bias, especially when you consider their reliance on animal models and cell studies, while at the same time ignoring the randomized controlled trials on humans refuting their claims.
The clinical trials it leans on most heavily, including the Minnesota Coronary Experiment and the Sydney Diet Heart Study, used margarine containing trans fats; a type of fat that has since been banned because of how harmful it is. Attributing the negative outcomes in those trials specifically to linoleic acid, while ignoring the presence of trans fats, is a significant confounding problem the paper never adequately resolves.
Another central claim from the paper is that linoleic acid, being highly susceptible to oxidation, gets incorporated into LDL particles and oxidizes them. They believe oxidized LDL is a better independent predictor of heart disease than total LDL. The argument is that linoleic acid could lower total cholesterol but still increase heart disease risk by raising oxidized LDL.
However, evidence from randomized controlled trials confirms that linoleic acid intake does not increase oxidative stress markers. This makes the oxidized LDL claim completely theoretical at this point in time.
Other claims made by the paper are based on historical trends. For example, the rise in obesity coupled with the rise in seed oil consumption. As mentioned in the introduction, it's unfair to pin these correlations on one thing. Many other variables have increased as obesity has risen as well: sedentary lifestyles, overall calorie consumption, stress, food availability, etc.
Final Thoughts
The discourse around seed oils is really just a cautionary tale about the way we analyze health in general. The body is a complex system. When people try to pinpoint one specific mechanism as the root cause or magical solution to all of our problems, it's rarely going to work.
Seed oils aren't bad, but a lot of the foods they are found in probably are. It's this association which has caused a great deal of confusion. If someone takes the circuitous route of quitting junk food because they heard seed oils are bad, in the end they still did a good thing. People who feel better after quitting seed oils are likely noticing the effects of eating a less processed diet overall.
But if you're looking for the true culprit of our current health problems, it's highly unlikely to be seed oils. The research showing it is safe (or even slightly beneficial) is of higher quality than the contrary. But we know how these trends go; they take on a life of their own until something else comes along. There was the low fat craze, followed by the low carb/keto craze, and now we're in the midst of the seed oil craze.
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This story was originally published April 14, 2026 at 10:25 AM.