Seed Oils: A Provocatively Reasonable Take
Today, I’m taking a different approach—one I hope you’ll find original, thought-provoking, and practical.
I’m fascinated by the seed oil debate for two reasons: (i) the data are complex and often contradictory, and (ii) it’s surprisingly hard to get people to hear what I’m actually saying—rather than what they assume from a headline, thumbnail, hook, or framework of the conversation, such as the identity debate partner sitting across from me.
Deciding whether to reduce the intake of seed oils—or more broadly omega-6 fatty acids—can be confusing, but the right answer for your health is hidden in the nuance. Understanding this debate is the first step to making informed choices that protects your long-term metabolic health.
So today, I’m taking a different approach—one I hope you’ll find original, thought-provoking, and practical.
First, I’ll start by outlining, in broad strokes, what I believe and what I do.
Then, we'll dissect the common arguments against seed oils, and I'll rate the rigor of each claim.
Finally, I’ll arm you with question to ask yourself to decide what makes the most sense for your own health and how to better assess such claims and arguments made about health and nutrition more broadly.
At a High Level: My Stance on Seed Oils
In short, I believe seed oils—here defined as highly industrialized and processed oils extracted from plants using “harsh” chemical and heating methods—are unnecessary at best and harmful at worst.
That’s the KISSS ‘keep is super simple stupid’ version. And if you want to leave now, you can’t. But I wouldn’t recommend it.
I personally avoid sunflower, safflower, corn, and canola oil in my diet.
My decision follows the “precautionary principle.”
We still don’t fully understand these industrialized seed oils, but the balance of probability suggests they’re more likely to be harmful than beneficial—at least compared to more natural fat sources such as extra-virgin olive oil, unprocessed nuts and seeds, and, yes, animal-based fats like ghee or tallow.
Now, some of you may be thinking, “Wow, Nick. Way to be anti-climactic.”
But please pause and consider how I said what I said as compared to what is often said.
I am NOT claiming that seed oils are “toxic engine lubricants in a conspiracy by Big Food and the academic elite to keep you sick.” While that may sound like parody, many of you know it’s a fairly accurate summary of a common belief.
My stance is simpler: I’m curious and suspicious.
The evidence on whether—and/or to what extent—seed oils are harmful is unclear, so all else being equal, I choose fats I believe are more likely to be health-positive.
Do you see the distinction?
With that in mind—and with full transparency about my own decisions—let’s take a clear-eyed look at the most common arguments against seed oils.
Arguments Against Seed Oils
Our ancestors didn’t eat this much omega-6 (linoleic acid)
The first “sin of the seed” is its high proportion of omega-6 fat (mostly linoleic acid).
Estimates vary, but our ancestors likely consumed about 2% of their energy from linoleic acid, whereas those in the modern Western world consume closer to 10–12% of calories from omega-6 fat.
This evolutionarily unprecedented rise in omega-6 intake, roughly paralleling an equally unprecedented obesity epidemic, paints a concerning—albeit correlative and circumstantial—picture.
It’s interesting, and it offers fodder for hypothesis generation. But, as many of you know, it’s not sufficient evidence to claim that high omega-6 intake causes obesity or negative health outcomes.
In fact, most evidence suggests that high intake and tissue levels (including adipose tissue levels) of omega-6 fatty acids are linked to positive health outcomes.
Taken alone, I’d give this argument 1.5 out of five stars for rigor.
A high omega-6/omega-3 ratio is inflammatory
If we dig a step deeper, we can consider not just omega-6 levels but also their relationship to their biochemical “fraternal twin,” omega-3. Unlike omega-6, omega-3 fats are generally regarded as beneficial for the heart and brain, and as anti-inflammatory.
While figures vary, an omega-6/omega-3 ratio at or below 4:1 is generally considered “optimal,” whereas those eating a modern Westernized diet tend to have a ratio around 16:1.
The question: Does this cause poor health outcomes?
First, the case for “Yes.”
In humans, it’s difficult to change the omega-6/omega-3 ratio without altering other variables. But in animal models, genetic modifications allow researchers to adjust the ratio while keeping the rest of the diet constant. In such studies, increasing the ratio does appear to worsen health outcomes—compelling evidence, in my view.
However, when we look at humans, the picture gets murkier.
A higher omega-6/omega-3 ratio is indeed associated with worse all-cause mortality (below, left). Case closed? Not quite.
In one UK Biobank study, a higher ratio correlated with worse all-cause mortality; but higher levels of both omega-6 and omega-3 individually were associated with lower all-cause mortality.
Even more interesting: the lowest mortality was seen in people with high levels of both omega-3 and omega-6 (below, right).
This is not a mathematical contradiction—it can be reconciled by recognizing that both omega fats may be beneficial overall, but that boosting omega-3 intake is more important. On a population level, a low denominator (omega-3) may be a bigger concern than a high numerator (omega-6).
My take: Beyond a certain threshold, a high omega-6/omega-3 ratio might be enough to cause negative health outcomes. However, this does not justify vilifying omega-6.
When consumed as part of a mostly whole-foods diet, foods rich in omega-6 are probably not a problem.
But very high seed-oil intake, combined with low omega-3 intake? Likely harmful—even just considering the omega-6/3 imbalance.
I’d give this argument three out of five stars for rigor. Personally, I aim to keep my omega-6/omega-3 ratio at 4:1 or below.
For more on this topic, read THIS letter or see the below video.
Linoleic acid & oxidation susceptibility
Let’s go another level deeper. One concern about linoleic acid is that it’s “fragile” and prone to oxidation, a process that can lead to inflammation and other negative health effects. Linoleic acid can be oxidized either before consumption or after it’s inside the body.
This means the individual’s metabolic status and overall “oxidation environment” may—indeed, likely does—matter.
For example, excess body fat can raise levels of myeloperoxidase (MPO), a marker of oxidative stress and an enzyme that oxidizes fats, including linoleic acid, in tissues and in circulating lipoprotein particles such as LDL.
It’s plausible, then, that in someone with obesity, higher omega-6 intake could cause more metabolic harm (via oxidation inside the body) than it would in a lean, healthy individual.
This raises the interesting possibility that obesity is a “seed oil (omega-6) susceptible” metabolic state.
A Short Note on 4-Hydroxynoneal (4-HNE)
Now, I’d be remiss not to mention 4-HNE—an aldehyde formed during the oxidation of omega-6 fatty acids. It’s a fascinating yet problematic compound, and one that probably deserves an entire newsletter of its own.
In brief, 4-HNE promotes cell death and metabolic dysfunction and accumulates in a range of chronic diseases, from Alzheimer’s and cardiovascular disease to cancer.
Focusing on cardiovascular disease as an example: 4-HNE can bind to ApoB on LDL particles, encourage foam cell formation, drive inflammation, and ultimately worsen atherosclerosis.
Interestingly, the primary source of 4-HNE is not dietary omega-6 fats but the body’s own internal production. For that reason, I’d prioritize reducing the body’s overall oxidative environment rather than fixating solely on omega-6 intake. Such an approach can still include a diet containing omega-6–rich foods.
But—bottle of industrialized oil to my head—if you were to ask me whether I think a high intake of “seed oils” could exacerbate chronic disease via 4-HNE generated inside or outside the body, I’d need to respond, “yes, it should be one concern.”
And, I’d add, “I think it’s likely a larger concern if you have pre-existing metabolic disease, e.g. obesity.
On balance, I’d give this argument 3.5 out of five stars.
And for more on 4-HNE, HERE is an excellent review article.
Okay, now we’ve looked at a few anti-seed oil arguments—and how they hold up under scrutiny. But next is where the debate gets truly interesting, and often confusing.
The arguments about industrial processing, 'toxic' chemicals, and industry influence are frequently used to provoke fear, but what does the evidence actually say?
And how can you empower yourself to better evaluate those often contradictory health claims?
In what’s to come we’ll explore:
Whether “Toxic” processing chemicals are a real concern
Big Food’s Influence (and where the conspiracy theories miss the mark)
What to make of a mountain of personal testimonials
My personal framework of questions to ask yourself when evaluating health and nutrition claims
And the final “argument” that… isn’t an argument at all
