Are seed oils inflammatory? Do they trigger inflammation? This is probably the number one question we've gotten over the last several months. So today, we look into it. Now, I know there's 9,000 other questions about seed oils, but in order to make sense of things, in order to get some clarity, we need to tackle things one question at a time, so this video is exclusively focused on inflammation, alright? But feel free to ask any other seed oil questions below in the comments, insulin resistance, oxidation, weight gain, whatever you want, and we can make videos on all of that. Now, I realize seed oils have become this hugely controversial topic, very emotional on the internet, people have very visceral feelings about them. Not me. I couldn't care less, don't love them, don't hate them, no feelings. We're just going to look at the science.

and see what it says. If seed oils look great, okay. If they look terrible, fine. I don't get paid by seed oil industries or any of these things that people ask online, so zero connections, zero feelings. We'll start by looking at the effect of different types of seed oil on inflammation, what has the science figured out? Next, we'll look specifically at heated seed oil, which is a very common question. If you cook with it, does that have a different effect on inflammation? Third, we'll look at a little bit of the why, the underlying reasons for the effects of seed oil on inflammation, and lastly, we'll look at individual variability, susceptibility, what is known about that. Alright, let's get into it. So, there are different ideas about this out there on the internet. One idea is that all vegetable oil is inflammatory, another idea is that it's specific to seed oils, so seed oils are inflammatory but things

like olive oil and avocado oil are much better, and a third version, a third idea, is that it depends on the content of omega-6s, of linoleic acid, so we're going to investigate all of this by looking at seed oils in increasing order of their linoleic acid content. So, on one end of the spectrum, we have flaxseed oil, probably the least controversial seed oil because it's high in Omega-3s, alpha-linolenic acid. And it's pretty low in omega-6s, only 14% of its calories come from linoleic acid. Now, what I normally do when I'm investigating a topic is I start by looking at some meta-analyses, so large studies that pool together several different trials, to get a sense of the big picture, and then I dive deeper. Right? So that's what I did. This

meta-analysis of randomized controlled trials measured the most common inflammatory marker, C-reactive protein or CRP for short. It pooled together eight individual trials looking at flaxseed oil, and overall there was no significant effect on CRP level. Here's another meta-analysis, this one's bigger, it pooled together 12 randomized controlled trials, all looking at flaxseed oil and inflammation, and again C-reactive protein was not significantly affected. This second meta-analysis also looked at other inflammatory markers in addition to CRP, and some actually changed in the direction of benefit, for example interleukin-6 or IL-6 was significantly reduced on flaxseed oil. So at least for flaxseed oil so far, it doesn't seem to be pro-inflammatory. Not going to be a surprise for a lot of people because flaxseed oil is rich in Omega-3s which can

actually be anti-inflammatory, so we're going to move on and look at other oils, but before we do, just want to make a really important point. When I'm investigating a field like this, I already know going in that there's going to be variability. There's always variability, so I dug around for a study that goes against the trend, a study that finds an increase in any inflammatory marker on flaxseed oil. Altogether, I went through 17 separate trials, all using flaxseed oil. 10 found no significant change in any of the inflammatory markers they looked at, six found a significant reduction of at least one inflammatory marker, and I did find one with a significant increase in one marker. This trial reported an increase in the inflammatory marker TNF after taking flaxseed oil. Now, out of the 17 total trials, several others looked at this specific inflammatory marker and did not see a significant change, including larger trials, trials that used the larger dose of

flaxseed oil and trials that followed people for just as long or even longer than this one, and we have meta-analyses that pool studies together and didn't find this either, weren't able to reproduce this result, so why am I digging around for an outlier and bogging now this video instead of just giving you the bottom line? because understanding these principles is more important than the final answer, we can find variability in any field, no exception, if we dig hard enough. I could tell you from experience if I go into the lab and run the same experiment 10 or 20 times I'm going to get an outlier or two, this is why in science we focus on reproducibility and on balance of evidence, so just to emphasize how crucial this is in terms of information we find on the internet and how it's presented to you, I could go on Tik Tok and show you this study alone and none of this

and say see? flaxseed oil is poison, everybody needs to stop eating it, and that would confuse a lot of people, but hopefully now you wouldn't be confused because you've seen the big picture. okay, so the balance of evidence for flaxseed oil is pretty strong that it's not a pro-inflammatory food, period. so for the simplest idea, that all vegetable oil is inflammatory or all seed oils are inflammatory, period, that doesn't seem to pan out. alright, but flaxseed oil is mostly Omega-3s, so this is not exactly a massive scoop, so let's get to the real stuff. next up, we have canola oil, aka rapeseed oil, but that name sounds terrible, so they came up with this alternative name canola, which is a contraction of Canada oil, and it just sounds more consumer-friendly, and canola is high in monounsaturated fats, kind of like olive oil, and it's about 18% linoleic acid,

and with Canola, I start to see a lot of controversy and a lot of people scared of it and asking if it's inflammatory. So, in this trial, people were asked to add one tablespoon a day of canola oil to their food for two months, and CRP, C-reactive protein, was not significantly different after the exposure to Canola Oil. Another really common question is how do these oils compare to other types of fat, like saturated fat for example? So, this trial compared saturated fat with omega-6s. They gave people similar foods but replaced saturated fat with unsaturated fats, using canola and sunflower oil, which we're going to look at in more detail in a minute. The omega-6 intake was roughly doubled in that seed oil group, and there was no significant difference in several inflammatory markers, CRP, IL-6, and interferon, after the exposure to seed oil or compared to the

saturated fat group. This other trial compared canola to olive oil, which is considered much better by a lot of people, so it's an interesting comparison. And they actually found a reduction of CRP both on the canola and on olive oil, and no clear difference between the groups. So, so far this sounds kind of similar to the flaxseed oil picture; most trials don't find much of a difference, and then a few might suggest a reduction. Now, let's look at some meta-analyses to get a sense of the big picture. This systematic review and meta-analysis looked at 42 randomized controlled trials using canola oil, and it found no significant effect of the oil intervention on inflammatory markers. And it also looked at comparisons between canola oil and other specific oils, for example, olive oil, and there was no significant difference in CRP level between the two. So that's canola, but again, canola is mostly monounsaturated fat, only 18% linoleic acid, so

if linoleic acid is the real problem, canola wouldn't be the best test anyway, so let's just keep going up and up. Next, we have sunflower seed oil. There are many types in the market, but the standard type is 20% linoleic acid. So here's an example. In this trial, people were told to consume one tablespoon of sunflower oil every day in the morning for four months, and it was double-blind, so they didn't know what type of oil they were eating. And a really interesting particularity about this trial, a lot of trials don't give a ton of detail on the oil they use, but this one specifies it was refined oil, which is usually treated with chemicals and heated and not the cold-pressed kind that some people believe to be safer. So this could be a more stringent test of the safety of these oils, and people consuming it did not have a significant

change to CRP level after the four months. Quick note on compliance: a lot of these trials provided the oil to the subjects in a bottle and then after the intervention often they collect the bottle with whatever's left so they can kind of see how much was consumed, some trials go beyond that and actually measure the blood levels of some fatty acids in the participants because those change depending on the fats that we eat, and other trials go even farther beyond that and we'll look at some examples in a minute. So here's another example, we're still looking at sunflower seed oil, this trial asked people to consume about two tablespoons every day, added to their salad or rice or other foods, and at the end did not see a significant effect on CRP level. Here's another one that compared sunflower seed oil to isocaloric saturated fat, mainly from butter. Some inflammation markers actually seemed lower on sunflower seed oil and they even concluded a high

omega-6 polyunsaturated fat intake does not cause any signs of inflammation. Instead, omega-6 polyunsaturated fats may act as anti-inflammatory. Okay, but that's just one isolated trial and this is their phrasing, who cares, kind of, so what do the meta-analyses show? This one looked at nine trials on sunflower seed oil and there was no significant change to several inflammatory markers: CRP, TNF, IL-6, and ICAM. So that's a look at sunflower seed oil, let's move on to oils that are more concentrated in linoleic acid, 50% and higher, big guns like soybean and corn oil. Just a quick note before we get to those that sesame oil is about 45% linoleic acid. I've seen two trials on it, one found no significant change to CRP and the other actually suggested

a decrease in one inflammatory marker, and this review went over the evidence on sesame oil and concluded sesame oil research shows promise in reducing cholesterol, inflammation blah blah we're only focusing on inflammation today. okay, let's get to the big cats, 50% and over linoleic acid. soybean, safflower, corn oil. this is where the rubber meets the road and these are some of the most controversial seed oils out there. so next I looked at soybean oil which is about 50% linoleic acid. here's one trial where patients were on Parenteral nutrition, which is where you get your nutrients diluted in a solution and straight into your bloodstream if you can't eat for some reason, maybe right after a procedure, so this is really interesting data to look at, among other types of administration, because number one, you know exactly how much is going in,

and number two, it's going straight into your blood, so if there's an issue with these oils, it might cause a problem there. So they split the patients, half were getting an olive oil-based solution, half were getting a soybean oil-based solution. So there was a five-fold difference in soybean oil intake between the two groups, and they received these intravenous infusions for three months, and it was also double-blinded, so they didn't know which one they were getting, but C-reactive protein level was not statistically different between the two groups. Okay, so that one is kind of cool to look at because they're injecting the oil straight into the bloodstream, in a way, but at the end of the day, we want to look at normal administration, eating it. So this trial compared soybean oil to flax seed oil and fish oil, so three groups, all delivered in capsules, and people took them for two months, and at the end, there was

no significant change in inflammatory markers on any of the oils. Here's a recent review that summarizes the evidence on soybean oil. They say soybean oil is a leading edible oil consumed globally and in the U.S. and they conclude it has no significant effect on markers of inflammation. They elaborate a little bit, evidence to date convincingly indicates soybean oil does not increase markers of inflammation. Okay, next I looked at corn oil, which is 52% linoleic acid. This trial looked at corn oil compared to coconut oil, pretty high doses, four tablespoons a day, and they actually hid them in muffins and rolls, so a different method of administration, and there was no significant effect on C-reactive protein in either group. Here's another one comparing flaxseed oil to corn oil for three months, two tablespoons a day added to food.

flaxseed oil lowered one of the inflammatory markers tested. Corn oil had no significant effect on any of the inflammatory markers they investigated. Another one looked at people with diabetes or metabolic syndrome, which is good to look at different populations, some healthier, some sick, so we get a more complete picture. So the participants were given corn oil or fish oil supplements for two months, and they actually confirmed that people took them by measuring their blood level of fatty acids, and CRP was not significantly different in either group. So that's a look at corn oil. Now we still have one of the big dogs to come, safflower oil, which has one of the biggest linoleic acid contents. But before we get to it, two oils that are less popular are hemp seed at 54% linoleic acid and grapeseed at 70%. And I've seen one trial for each, the trial on hemp

seed found no significant difference in C-reactive protein, and the one on grapeseed actually reported a decrease in several inflammatory markers, although I don't necessarily believe it. First, because it's just an isolated trial, and second, because there was some weight loss during the trial, so the benefit could be coming from that. So let's look at safflower oil, which is one of the top dogs at over 70 percent, up to 80 percent of the calories coming from linoleic acid, and it's also commonly used. So this trial gave people safflower oil for three months, one tablespoon a day, and there was no significant change to CRP or IL-6. This one's similar, also three months but two tablespoons a day, and it was blinded, so people didn't know what oil they were consuming, and there was no significant change to CRP. This one actually suggested

a decrease in one of the markers after three months on safflower oil, one tablespoon a day. This one saw a decrease in CRP and concluded eight grams of safflower oil daily improved glycemia, inflammation and some other stuff, we're focusing on inflammation today. And another one saw no significant change with safflower oil over three months. And this meta-analysis looked at several of these oils separately: soybean, sunflower, sesame, corn oil, and safflower oil, and pooled a few trials for each and looked at several inflammatory markers, four or five different ones, and found no significant difference in any of them for any of those oils. Now, we could hypothesize about dose, maybe you need to go from a low dose of linoleic acid to a very high dose to see an effect. So this trial used the largest dose I've ever seen reported. First, they put all the

volunteers on a diet low in omega-6 for a couple of weeks to level everybody out, then they split them into groups and put them on different oils for a month. One group got olive oil, and one got canola, and one got sunflower seed oil, but a huge amount. They were getting almost 500 calories a day from omega-6s alone. 20% of their calories were coming from sunflower seed oil. Just for perspective, most health organizations recommend getting about five to ten percent of our calories from omega-6's, ballpark. These guys were getting over 18 percent. And they found neither an increase nor a decrease in CRP and other inflammatory markers on any of the diets. So even for the highest reported intake, almost an unreasonable intake of seed oil, we still don't detect an inflammatory signal. Okay, so dose doesn't seem to make a big difference. What about time? Maybe these oils seem

fine inflammation-wise over weeks or months, but if you eat them for years and years, then you pick up an inflammatory signal? A little strange because inflammation normally kicks in pretty quick after a stimulus, but, you know, it's possible. We'll look at some longer trials in a minute in the scale of years, but another thing we can also do is we can ask if people who normally eat larger amounts of linoleic acid in their normal lives, if they have more inflammation. What's been reported is that higher linoleic acid intakes are associated with lower concentrations of C-reactive protein, IL-6, and IL-1-beta inflammatory markers, so the opposite of what would be expected if they were pro-inflammatory. Now, maybe people are not being honest and they say they eat a lot of linoleic acid, but they really don't? So we can ask this question in a different way, linoleic acid is

an essential fat. That means our body doesn't produce it; we need to get it from our food. That also means that whatever linoleic acid is in our body came from something we ate since we can't produce it. So, we can measure people's linoleic acid levels in the body and see if that goes in the same direction as the dietary intake data. And what they found was an inverse relationship between circulating levels of omega-6s and inflammatory biomarkers. That means the higher the omega-6 levels in the body, the lower the inflammatory markers, so it matches the dietary intake data and again, the exact opposite of what we would expect if the omega-6s were pro-inflammatory. So, that's the general picture regarding seed oils and inflammation. Next, we're going to look at heated seed oils, which is a very common question. Before we go there, just want to

point out real quick, we've been looking at levels of inflammatory markers in the blood after chronic intake, so consistently eating the oil for weeks or months. There are some studies out there that look at acute effect after one meal and changes in expression levels of inflammatory markers inside certain cells in different tissues, so mRNA levels inside cells, and those often go up with fatty meals in general, they go up with polyunsaturated fats, they go up with saturated fats, and the relevance of these acute oscillations in gene expression isn't clear because it often doesn't even reflect the actual level of the inflammatory marker in the blood. In fact, it sometimes goes in the opposite direction, give the oil to people once and acutely after that meal you see an elevation of some of these mRNAs inside the cells, but give the oil to people for months, the same oil chronically, and the actual level of the inflammatory marker in the blood stays the

same or even goes down. So just going over this, so you have all the information and if you find this later you're not blindsided, you don't go oh does this change everything, I didn't know this existed. Another quick note, people always ask about whole sources of fat like nuts and seeds, there's some data comparing nuts to oil for inflammation, for example in Predimed the groups with extra olive oil and extra nuts both lowered some inflammatory markers and there was no significant difference between the two groups. This is another trial that looked at olive oil versus walnuts versus almonds, so comparing the three, and also didn't find a clear difference between the three for inflammation. As for seed oils, which is the topic of today's video, I've seen very little data comparing them to whole seeds or nuts. A few meta-analyses look at flaxseed oil versus the actual seeds and overall I see no convincing superiority of

one over the other, so it's basically personal preference. Okay, let's talk about heated oil, really common question a lot of viewers ask, so I really dug, and there are fewer studies on heated oil specifically, not surprising. Anytime we ask a more specific question, there's going to be less data, but I did find a few. So this one, for example, was a randomized controlled trial. People were given either peanut oil or corn oil to cook with and to replace their normal cooking oil, and after six months, there was no significant difference in CRP level in either group. This one was similar but compared sunflower seed oil to coconut oil, also for cooking, and it lasted two years, and there were no significant differences in CRP at the end. This one's very interesting; the level of control they had was unusual. Three meals a day were prepared by the research team.

and provided to the subjects, all cooked in soybean oil, breakfast, lunch, and dinner. For two months, the researchers visited the subjects, served every meal, and checked their compliance, so they checked that they actually ate, and many of the meals were fried: fried fish, fried rice, stir-fried vegetables, all in soybean oil. And they measured several inflammatory markers, and eating all that food cooked in soybean oil did not significantly change any of them. Now, maybe light heat like sautéing or something, is fine, but intense prolonged heating is what blasts these oils? In fact, it has to be that way, right? If you heat anything long enough, you heat a stick of celery long enough, eventually it becomes a lump of coal, and it's not good to eat, so it's just a question of how long it takes. And this is such a common question that I really wanted to dig

more into this, so I kept looking for trials that looked at more prolonged forms of heating. So, in this randomized controlled trial, they gave people safflower oil, heated safflower oil, or olive oil in capsules for one month. And the heating procedure was two hours at 240 degrees Celsius, so pretty intense. And it was a blinded trial, so they didn't know which one they were getting. And there was no significant difference in inflammatory markers on any of the groups. Okay, what if we deep-fry the oil? I think that's what they do at Burger King and places like that? That has to ruin it, I mean, it's just a matter of time, there's no doubt. Now, at this point, it was getting harder to find trials that did it because it was a more and more specific question, but I did find some that deep-fried the oil for an extended period of time.

but at this point, most of these trials look predominantly at acute effects after one meal. This one used sunflower seed oil deep-fried for a whole hour and then stored in the fridge until it was consumed. A bit atypical, I think, but okay. And they had two groups: healthy people and people with heart disease. In the healthy ones, there were no significant changes to the inflammatory markers with the unheated oil or with the deep-fried oil. But the folks with heart disease, it was interesting, the unheated oil lowered some of their inflammatory markers, and the deep-fried oil raised some of them. Now, again, this is only an acute effect after one meal, so it's entirely possible, I would say it's plausible, that if someone ate that stuff consistently for a while, yeah, the effect might be much stronger. I mean, that's what I would expect. Or if you deep-fry

the oil repeatedly, right? Over and over, I think that's what they do in some of these fast food restaurants. So, I did find a group in Spain that does the experiment like that. They deep-fry the oil and then let it cool down and then deep-fry it again, 20 times in a row, the same oil sequentially, right? And then give it to people. Now, don't ask me how much they're paying these volunteers to go through that, I don't know. Unfortunately, in this experiment, they don't look at inflammatory markers in the blood, and it's only an acute effect after one meal. I don't know if you could give this stuff to people chronically for months, it's probably not ethical, but they do report some molecular changes that suggest that olive oil might resist that insult better than regular sunflower seed oil, and that you might be better off if you had

to eat something deep-fried 20 times, that you might be better off, that it might be healthier to do it with olive oil, and I have no trouble believing that. So when we put everything together, we have a very strong balance of evidence that seed oils in general, unheated seed oils, don't show a clear effect on inflammation, across seven or eight different types of seed oils, with widely different linoleic acid contents, in different doses, in sick people and healthy people. Cooked seed oils for the most part, also no clear effect on inflammation even after cooking exclusively with seed oil for months or even years in some cases. When we get to extreme exposures like deep frying for hours or deep frying the same oil for dozens of times, then we might have an issue, some data suggests that, I'd be surprised if that weren't the case at some point. So that's the data. Now, this is for seed oils themselves,

not junk food that happens to contain some seed oil. Sometimes I see people online conflating this, saying I cut out junk food and I felt better, I got healthier, must have been the seed oils. Oil on a salad or to sauté something is one thing, and junk food with or without seed oils is a completely different beast, let's get that very clear. Quick note on funding, a lot of times on emotional topics like this people ask who funded the study so I went through and I checked, majority of studies that we looked at were either funded by governmental grants or academic grants, so from universities, some were industry-funded, just to give you an idea, the largest ones we looked at that used the seed oil for cooking for extended periods of time, one of those was a government grant and the other was funded by the coconut board so there was no incentive to favor

the seed oil, which was used as a comparison in that trial. And this was the case with several of these trials. For example, sometimes they're funded by a company that makes fish oil supplements, and so they're testing the fish oil supplements, and they're using the seed oil as a comparison. So that's the general picture. The bottom line is exactly the same whether we look at all the trials or we exclude the industry-funded ones. In fact, I could have made the video and just shown you the ones that are funded by universities or governments. It would give you the wrong impression, so I don't want to do it that way. It would propagate this misconception that we assess and dismiss scientific evidence based on funding alone. So I'd rather give you more information and explain a bit more and not propagate confusion. So this is the general picture in humans. We're going to go over some individual variability in a second, and there's lots of data in rats.

and rabbits. I focused the investigation on the human data, I think for obvious reasons, and I went through a lot of studies. I can't guarantee that I found every study ever published; it's virtually impossible to guarantee that, but I tried to give you a perspective that is reflective of the balance of evidence, and the balance of evidence seems very consistent. As one review concluded, despite the concern that omega-6 fatty acids increase inflammation, current evidence from studies in humans does not support this view. Okay, so if seed oils are not pro-inflammatory, where does this idea come from? I mean, it's so pervasive; it's all over the Internet. Linoleic acid can be converted to another fat called arachidonic acid, which can then be converted into a number of molecules that can play an inflammatory role. So that's the basis for

this idea, so it would make sense if the net effect of linoleic acid in living, breathing humans turned out to be pro-inflammatory. That would not be an unreasonable hypothesis, but what we do with hypotheses is we test them, we don't assume. Because maybe in humans it doesn't get converted for some reason, or maybe it does but it also does some other stuff that makes up for it. And it turns out that's exactly what happens. In humans, the production of arachidonic acid from linoleic acid is tightly regulated, so even wide variations in dietary linoleic acid do not materially alter the actual amount of arachidonic acid. In fact, decreasing dietary linoleic acid by up to 90 percent, so 10 times, was not significantly correlated with any changes in arachidonic acid levels, and increasing dietary linoleic acid up to six times more

does not increase tissue arachidonic acid. So, it doesn't get converted much in vivo in humans. As for the other possibility, that it might do other things in parallel that might make up for it, that also pans out. These authors explain it: If one takes off the blinders (these guys are brutal) and examines the entire arachidonic acid metabolome (so all the molecules that get produced from it), one finds a constellation of metabolites (so a bunch of different molecules). Some are pro-inflammatory, some are anti-inflammatory. The net impact on human metabolism is virtually impossible to predict (that's why we have to test things, not assume). So, to label the entire class of omega-6 metabolites as pro-inflammatory is painfully naive. So, this is a lesson we've learned in many previous videos, and it's a crucial one. We don't make logical leaps from biochemical pathways or from isolated molecules to a net

effect in living, breathing humans. We have to test it. And this goes for the heating questions as well: seed oils are unstable, seed oils have double bonds. What's the health effect in a human eating them? That's the bottom line. Okay, so maybe eating seed oils is not inflammatory for most people, but maybe some people have a particular susceptibility? It's like that for most things; why would this be any different? So, there are some genetic studies looking at people with different mutations in that pathway we just looked at that converts linoleic acid to arachidonic acid and beyond. So, they put people on a diet high in linoleic acid, and people with one specific mutation, their CRP level trended to increase. So, it's possible that there is a subset of people, maybe the more extreme cases, that have a special susceptibility. So, if somebody has high inflammatory markers or has an inflammatory condition and they want to try

moderating the seed oils, I don't see a problem. Also, for people who just don't like them, or if you prefer an omega-3-rich oil like flaxseed oil for example, or if you just heard so much stuff on the internet about seed oils that it stresses you out and you'd rather not, don't eat them! They're not essential, no oil is essential in the diet, plenty of other healthy fat sources. And for those who do want to include some seed oils, who want to put some canola oil on their salad, who want to sauté in some sunflower seed oil, inflammation is not a convincing reason not to do it, not supported by the evidence, despite what people might repeat on social media. Seed oils have become such an emotionally charged topic that we're not even supposed to discuss this anymore, we're not supposed to share studies showing benefit, people complain you're promoting

a toxic food. promoting! Guys, this isn't sales. I don't make money from you buying seed oils or not, and if the science doesn't align with what we've heard before, the solution is not to stop showing the science. And the emotional language. promoting, vilifying, demonizing. This just distracts us from simply trying to figure things out. At the end of the day, we protect our health by calming down and basing our views on evidence, not stories. Alright? I hope this helps. Take care. Let me know any questions below. See you next week.

Are Seed Oils Inflammatory?! (The Evidence No One Shows)

Are Seed Oils Inflammatory?! (The Evidence No One Shows)

Scripts

Are Seed Oils Inflammatory?! (The *Evidence* No One Shows)

Are Seed Oils Inflammatory?! (The *Evidence* No One Shows)

Scripts

Are Seed Oils Inflammatory?! (The Evidence No One Shows)

Are Seed Oils Inflammatory?! (The Evidence No One Shows)