The Seed Oil Debate: Health Hazard or Hysteria?

are seed oils reallllyyyy all that bad? what we know and where we land

Instagram is such a funny place

On one hand, I follow women and fellow RDs that preach the narrative of “seed oils are so fine, soooo much research shows there’s nothing wrong with them”

and then a quick swipe and I’m on to another RD stating “seed oils are literally slowly poisoning us and our body over time”

Yeeessshhh 😩

No wonder our field is constantly discredited - we can’t even agree on a stance on one of the most commonly used products in the modern food era

So I will say this:

• Seed oils are controversial

• There’s no one “perfect” answer

• We’re still learning about seed oils from a research perspective

• We also have to lean on common sense

And as a result, this is the Roots to Leaves take given alllll the above

Let’s start off with the basics: What Are Seed Oils?

Seed oils are exactly what they sound like—oils extracted from the seeds of plants like

• sunflower

• safflower

• soybean

• canola (rapeseed)

• corn

• cottonseed

• grapeseed

and they’re used in a lot of everyday products —like basically everything

and their accessibility and contribution to the standard American Diet has made a pretty hot topic….so where do we land on the topic?

The Rise of Seed Oils: A Lil History For Y’all

So why have seed oils have become such a hot topic? Largely because they are so. dang. popular.

See seed oils are a relatively modern addition to the human diet (canola oil first started in the 1970s and didn’t make GRAS until 1980s!!!)

Prior to the 20th century, most cooking fats came from animal sources like butter, tallow, lard, or from fruit-based oils like olive and coconut.

These fats were made through more straightforward methods: churning cream, rendering fat, or pressing whole olives. But in the late 1800s/early 1900s, everything began to shift.

Industrial Revolution + advances in chemical engineering = we can make oils from more things cheaper!

So come early 1900s, Procter & Gamble introduced Crisco —a hydrogenated form of cottonseed oil. It was shelf-stable, didn’t need refrigeration, and was positioned as “pure” and “clean” in comparison to lard or butter.

So why did seed oils take off? In many ways: cost.

Seed oils are significantly cheaper to produce than animal fats.

Soybeans and corn, for example are some of the most heavily subsidized crops. + technological advances made it possible to yield huge volumes of oil from what was once waste.

And because these oils were highly refined and shelf-stable, they could sit in warehouses and on grocery store shelves for months (or years) without going rancid.

sooooo…..

lots of oil

little cost

decade shelf life….

Obviously, our industry was excited

+ there were some other factors:

• Animal fats were rationed in WWII, so gov encouraged other oils

• 1950/60s began the heart disease scare and public messaging to go to veg oils to limit saturated fat (hence the rise of margarine…which btw later turned out to be horrible for you).

• Rise of ultraprocessed foods = desire for affordable fats that wouldn’t spoil or alter the flavor of packaged goods

Pretty soon….we became a nation dependent on seed oils

The Issues With Seed Oils:

Essentially, the argument against seed oils break down into 3 main categories:

1. the way it’s made/processed

2. the omega-6:omega-3 debate

3. some other emerging concerns around oxidation, mitochondria, etc.

The Processing Issue

So no matter where you land on seed oils, it’s a simple fact that seed oils are an ultraprocessed food

Let’s break down what it actually takes to make it:

1. Collect, clean, and grind the seeds – part is pretty harmless and standard.

2. Solvent extraction with hexane – Here’s where things shift. Hexane, a petroleum-derived solvent, is used to extract the oil from the seed meal. While it’s effective, hexane is also a known neurotoxin in larger amounts. And although manufacturers claim that most of it is removed, there’s little transparency around how much residue actually remains—and since the FDA does not monitor this, so we don’t know whether there’s no hexane on our canola oil or levels that would make us second guess our intake

3. Bleaching – To make the oil look more appealing, it’s filtered through bleaching to remove color. This process strips away some of the antioxidants like vitamin E and carotenoids, making them devoid of most nutrients (i.e. 1 oz sunflower seed = 7.5 mg vitamin E (50% daily requirements), 1 tsp sunflower oil = 1.5 mg vitamin E)

4. Deodorization – high-heat processing to eliminate odors. This neutralizes the flavor, but in doing it also generate small amounts of trans fats—which are strongly associated with inflammation, heart disease, fertility challenges etc. (i.e., butter = 0.03 g trans fat; cottonseed oil = up to 0.5 g)

+ chemical preservatives, like BHT and BHA, are sometimes added to enhance the shelf life of the oils which are considered to be EDCs.

Soooo basically

we’ve taken a seed—something that was never naturally oily—and subjected it to chemical solvents, extreme heat, bleaching, and deodorizing just to get a clear liquid fat that won’t go rancid on the grocery shelf.

common sense tells us — it’s probably not the healthiest food to have daily

The Omega-6: Omega-3 Debacle - All About Inflammation

Prob the most confusing part of seed oils is the whole omega-6 vs. omega-3 issue

Omega-3 and omega-6 fatty acids are both types of polyunsaturated fats (PUFAs) — and contrary to what some wellness corners might have you believe, we actually need both.

• Omega-3s (ALA) are known for their anti-inflammatory properties. They support brain health, hormonal balance, and even healthy ovulation.

• Omega-6s (LA), on the other hand, are pro-inflammatory — which isn’t inherently bad. Inflammation is a critical part of the body’s healing response. We need it for healing for example!

So if we need both, the issue isn’t omega-6s, but rather how much omega-6 in relation to omega-3s.

So it’s alllll in the ratio baby

Our ancestors likely consumed omega-6 to omega-3 at a ratio close to 1:1 or 2:1.

Today, that ratio is often closer to 15:1 or even 20:1 — largely because omega-6s are so dominant in the modern food supply, especially in the form of ding ding ding 🛎️ seed oils

and as a quick note, we don’t know the “ideal ratio” but most countries still advise for a smaller ratio nonetheless. Japan? 2:1. US or Sweden? 5:1. all sorta hanging around in that ball park….but no one recommends the 15:1 we’re maintaining now

so if we know that omega-6s = pro-inflammatory and omega-3s = anti-inflammatory, but we’re chronically overeating omega-6s, then common sense says

“hey, your body is likely in a low grade state of inflammation”

but what does the RESEARCH say? 🤔

honestly, there have been lots of studies that show that eating foods/diets with LA are linked to benefits

For example, the American Heart Association states that seed oils have a place in a healthy diet (when contributing to 5-10% of total calories)

Some studies, like this one found that intake of seed oils have no impact on dietary inflammation

Other major organizations have stated similar findings, especially when it comes to heart disease

with that, we also know that’s there’s typically another side to the coin here:

• Double blind RCT of 9,000 participants showing that when seed oils are used to replace saturated fats (like butter, etc), while cholesterol did lower, risk of death went up (conclusion, benefits of seed oils have been overstated annnddd this study was actually pushed down and not published for a looonnng time 🤔)

• Another single blind study showing that when saturated fats are replaced by seed oils, risk of death went up

• Study on mice showing that a diet rich in soybean oil compared to coconut oil leads to worsened insulin resistance and brain function

• This old school (1965) randomized study that asked people to have about ~80 g. seed oils per day (which is the average intake) and found that heart attacks and diabetes went up

• Study comparing countries seed oil intake that does a pretty good in depth explanation of its link to diabetes, athersclerosis, metabolic dysfunction, etc.

• Another study showing that men who had a higher omega6:omega3 ratio had more issues with fertility compared to those with higher omega-3 levels

• Study showing that increasing omega-6 intake in pregnancy can lead to early labor

• Study showing that PUFA intake may impact fertility, with decreased risk of fertility issues when DHA (i.e., omega-3 intake) went up in comparison to omega-6 (i’ll note, another one showed null results)

• Cross sectional looking at omega-6:omega-3 and finding that endometriosis was associated with higher omega-3 intake (and therefore, smaller ratio)

• Observational study on an omega-6 and pelvic pain due to increased inflammation

and then of course, there are some mixed reviews

like this meta-analysis, which basically just shows areas where seed oils outperform butter, and where coconut oil or beef fat outperform oils

or this one that shows while it can better cholesterol levels it can also lead to lipid oxidation, which is a whole other story 🤷🏼‍♀️

Bottom line? we know that

seed oils = potent omega-6 source

omega-6 = inflammation

inflammation = cascade of issues in the body

A few other concerns to highlight

but even outside of the omega6:omega3 issue, we see some other stuff going on with seed oils

• Intake of LA (omega-6) increased with oxidized linoleic acid metabolites, which are connected to mitochondrial dysfunction and chronic disease

• Rats fed sunflower oil had more free radicals in just 4 weeks

• Study showing that increased omega-6:omega-3 ratio can actually lead to negative impacts on lipid markers

• Reheating palm oil (which we do constantly in restaurants) linked to increased blood pressure and lipid oxidation

and we also know that in general, polyunsaturated fats (which make up seed oils with both omega6 and omega3 content) are unstable when heated and can oxidize realllyyyyyyy quickly

now again, there are also a lot of studies that show the opposite - especially when it comes to canola oil.

So the jury is still out.

so let me say this:

1. Do I think seed oils are the absolute devil, slowly poisoning us all? No

2. Do I think we’re massively over-consuming an ultra-processed food that was never part of the human diet until ~50-100 years or so ago? Absolutely.

3. Do I think we need to spend our lives doing everything possible to avoid seed oils? erm…that sounds exhausting. But we should be mindful and limit where we can.

4. Do I think it’s possible we find out that seed oils are actually super beneficial and this was all “pseudoscience?” sure.

But until then I’m going to lean on common sense, what we know about omega6 and inflammation, and proceed with caution around something whose long-term effects we are still trying to understand.

How to Spot Seed Oils In The Wild (and reduce our intake)