The Seed Oil Debate Revisited

Back in 2013, I put together a 3-part series on PUFA. I referenced several health influencers from different camps that all agreed that excess PUFA was bad for health.

I was persuaded to reduce my PUFA intake drastically. But unlike the low-carb Paleo crowd, I decided it mathematically made sense to reduce fat and increase carbs, because many of the fat sources favored by Paleo actually had a fair amount of PUFA. Also, I estimated it could take a few years to reduce stored PUFA levels, so going below a healthy baseline level for a while seemed correct.

A year later, instead of focusing on all PUFA, I narrowed my dietary limitation to seed oils and added back whole food sources of PUFA, such as nuts.

Here we are in 2022. I avoid seed oils, I’m lean, and my body temperature is higher than when I started reducing PUFA/seed oils. More on that later. So was I correct? Well, it seems this debate isn’t settled.

This year I noticed several smart people defending seed oils. And the people attacking seed oils the loudest these days have reduced credibility in my eyes. With that background out of the way, I want to reopen the seed oil debate, now that I’m older and hopefully wiser on the topic.

Why Are Seed Oils Bad?

When I started putting this post together, I thought of 4 reasons cited to avoid seed oils.

  1. High Omega-6 to Omega-3 ratios are unhealthy. Seed oils increase Omega-6 and this is inflammatory. This inflammation then leads to numerous health problems.
  2. Keto and Carnivore dieters often claim that saturated fat is better for heart health than seed oils.
  3. Seed oils reduce metabolism. Lower metabolism makes weight gain easier.
  4. Seed oils increase appetite, which leads to increased obesity risk.

The debate I see online seems to be focused on the first 2 items. I actually think the last 2 items are the most interesting.

#1 Inflammation

Seed oils may not be as inflammatory as previously believed. The 2018 study Omega-6 fatty acids and inflammation states:

…it is commonly believed that increasing dietary intake of the omega-6 fatty acids ARA or its precursor linoleic acid (LA) will increase inflammation. However, studies in healthy human adults have found that increased intake of ARA or LA does not increase the concentrations of many inflammatory markers. Epidemiological studies have even suggested that ARA and LA may be linked to reduced inflammation. Contrastingly, there is also evidence that a high omega-6 fatty acid diet inhibits the anti-inflammatory and inflammation-resolving effect of the omega-3 fatty acids.

I didn’t see that coming. What about oxidized seed oils specifically?

Kevin Bass found a study* showing that even after heating sunflower seed oil to 200 F for 24 hours, did not cause an increase in inflammatory markers when fed to pigs.

UPDATE 2024: Kevin appears to have deleted the tweet. 🤦🏽‍♂️

The “oxidized seed oil leads to inflammation” theory has some holes. It may still be true and we may need to dive deeper into the different oils to learn more, but it doesn’t appear to be as settled as I believed.

#2 Saturated Fat is heart healthy?

About 3 years ago, I posted that I no longer had faith in the Paleo argument, which has since been embraced by the Keto/Carnivore groups, that saturated fat is heart-healthy.

I decided that people who lied to me about carbs might be wrong with their contrarian views about saturated fat. So I tested this for myself. When I reduced my saturated fat, my blood work improved. Then my blood work got worse when I increased my saturated fat during an elimination diet. And when I reduced saturated fat again my bloodwork improved again.

Saturated fat defenders will often dismiss the most popular blood markers used to measure health. I’m not qualified to have that debate, but I have seen a strong trend away from the view that seed oils are worse for cardiac health than saturated fat.

This saturated fat vs PUFA argument is the least interesting to me because my diet is lower in all types of fat. Protein and complex carbs are serving me well.

#3 Metabolism

Does a diet high in PUFA reduce metabolism? This was brought up years ago by Danny Roddy, Ray Peat, and Matt Stone. Recently, the site FireInABottle has not only published technical articles on the topic but has uncovered historical examples of populations before and after seed oil was added to their diet.

My n=1 story is that drastically reducing seed oils for years increased my body temperature from 97.0 to 98.4, which I maintain today. I’m maintaining a lower body fat percentage with far less effort than when I had a lower body temperature.

If you follow the links on that page, you’ll see the case for why fat built with PUFA would generate less heat than saturated fat. Do seed oils with a high amount of linoleic acid send a hibernation signal to metabolism? Could this be one of the primary reasons for the global obesity epidemic?

I suppose with enough evidence I could change my mind that seed oils don’t have a negative impact on metabolism, but for now, I’m a believer.

#4 Appetite

Does the brain receive the satiety signal as quickly when the fat source is a seed oil high in linoleic acid? According to Hyperlipid, no. From Hyperlipid For Dummies:

Although carbs cause the increase of insulin which drives fat into fat cells, Peter points out that the fat signals when this process is to stop. Saturated fat signals for this process to stop once the cell is full, whereas linoleic acid stops the stop signal. This is a breakdown of how the fat cells communicate satiety with the brain.

This material is too deep for me to know if it is correct, but it is persuasive.

Conclusion (for now)

What I see online today is many accounts with low credibility are making exaggerated claims about the dangers of seed oil. Then some very smart serious people shred the weakest arguments as a way of dismissing the dangers entirely.

Maybe seed oils aren’t inflammatory. Maybe when combined with a reduction of saturated fat, cardiac blood markers improve. Both are possible. However, I don’t see anyone debunking the metabolic claims or the biochemistry Hyperipid discusses relating to linoleic acid and satiety.

I’ll continue to avoid seed oils. I am able to prepare my own meals at home. For most meals, I don’t need any oil. If I do, I reach for Extra Virgin Olive Oil.

Avoiding seed oils appears to be working well for me. I’m warm and my appetite is in check. In a world that is getting fatter every year, I’m the leanest I’ve ever been and the process feels effortless.

tape measure

Photo by Siora Photography


Add yours

  1. Glad you have re-visisted this as I was wondering about this too. Although not a seed oil, assume you are more relaxed on PUFA in oily fish?

  2. @S C – Great question. As someone that has consumed numerous cases of sardines in the last 5 years, if the PUFA from fish was problematic to my metabolism, I would know. My body temperature has remained 98.4.

    I did some searching and all I found was a cached image on DuckDuckGo to a Brazilian study, which is no longer online.

    2024 UPDATE: image is gone

    The chart shows very low Linoleic acid levels in sardines. Sardines like other whole food sources of PUFA have some Vitamin E, which many believe to be protective.

  3. I agree with your conclusion on seed oils. The truth likely lies somewhere in the middle, i.e. not as dangerous as some people say, but unlikely that it is healthy or a completely neutral source of calories.

    Personally, I’m not holding my breath for a definitive study telling me if it’s okay to eat seed oils, or telling me that it’s harmful.

    1. The burden of proof is on seed oils to show benefit. LDL reduction by it self isn’t sufficient to convince me. Of course, there will be no RCTs showing improvements in hard outcomes. And as with all biomedical interventions, it’s harmful until proven otherwise.

    2. Seed oil consumption is a great proxy for ultra processed, nutrient poor junk consumption. Generally, it seems to be an overall benefit to advise avoiding seed oils, as it’s hard to eat processed foods when you eliminate seed oils.

    At the same time, it’s unlikely that a little bit of canola oil to sear a steak is making a huge difference in anyone’s health, if one is avoiding all other sources of seed oils e.g. fried foods, chips and cookies.

    Overall, mechanistic theories, animal studies, observational studies are interesting from the point of view of pursuing an intellectual curiosity. I doubt that there will be robust evidence coming out proving benefit or harm of seed oil consumption. And until then, as with all interventions, it’s harmful until proven otherwise. There is just no need for anyone to be consuming them.

    Q: have you measured your omega 3 / 6 ratio? Curious to see how your results changed over time, and which test you ordered.

  4. @Woojin – You made an important point that I neglected to add.

    Seed oil consumption is a great proxy for ultra processed, nutrient poor junk consumption.

    If removing the seed oil, removes the crap food, was the seed oil guilty by association? Kind of like how boiled potatoes are attacked for the crimes committed by chips and fries.

    I have not tested my Omega ratio. I found a test on UltaLabs for $45. I’ll consider it, but I don’t know if it would provide actionable information for me and my current diet.

  5. Are there any other benefits you link to a higher metabolism/higher body temp? You cite leanness, what about energy levels, mood, mental clarity, anything like that?

    I’ve wondered before if there are tradeoffs to a higher/lower metabolism. Not sure.

  6. @HS – That is a great question. I’ll do the next post on this topic.

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