Search This Site!
Nutrition Past and Future

41 PUFAs Oxidize!

One of the unquestioned articles of faith for Paleo and low-carb believers is that polyunsaturated oils are just the worst. They join sugar and wheat among the great evils in nutrition, and this is something that the Paleo people just know. With this knowledge comes a deep sense of injustice. Polyunsaturated fats somehow got a free pass and became the favored fats in nutrition while saturated fats have taken all kinds of flak. After World War II the giant evil seed oil companies displaced the virtuous local dairy farmer in a silent coup, and our health has suffered ever since. Polyunsaturated fats are said to be so problematic because they are chemically unstable and prone to oxidation. To the low carber, the fact that saturated fats are solid at room temperature is an indicator of their essential goodness. That means they are more stable. That also means they are less fluid. Polyunsaturated fats are more fluid.

We are dealing with very basic information here. We should expect that everyone working in biochemistry and nutrition science knows all this. Therefore, one might assume that the mainstream argument against saturated fat was created by people who, at a minimum, knew the molecular structures of lipids. Nevertheless, there are untrained people who feel that their general awareness that unsaturated fats are missing some hydrogen atoms gives them an important insight into the causes of heart disease. They think they know better than the scientists. Here is an unfriendly message I received from a teenager who fell under the influence of the Weston Price Foundation website.

This would hardly be the first time a teenager has been led astray by that website.

This message was supposed to have set me straight about fats and heart disease. Once you get past its unpleasantness - and let's remember this was just written by a kid taking advantage of the anonymity of the internet - we see that this teenager assumes that the scientists who advise us about diet do not know that polyunsaturated fats are less stable than saturated fats. They all missed that back in school. Nutrition is so simple. Saturated fats can withstand high-temperature cooking. What else do you need to know to figure out heart disease?

This thinking gets a little more sophisticated with Paleo bloggers. Stephan Guyenet is here writing about how oxidized LDLs are responsible for heart disease, and he has a study to show us how that oxidation is caused by polyunsaturated fats. He's found a paper to make his point, which has information that he thinks will prove embarrassing to the mainstream of nutrition science. Apparently, in this study, we learned that LDLs are especially vulnerable to oxidation in those consuming diets with polyunsaturated fats, while those consuming more saturated fats have their LDLs suffer less oxidation. He wants you to know that saturated fat protects your LDLs, and so saturated fat protects you from heart disease. The media has ignored this, he says, maybe because he thinks this is a profound truth which the powerful seed oil people want repressed. He is bringing this to your attention, anyway. Thank goodness for his blog. He is doing his best to save us from heart disease by promoting saturated fat.

Guyenet has trouble avoiding contradicting himself. According to his reference, the most easily oxidized LDLs were found in those consuming more omega-3 fatty acids, which are highly unsaturated and vulnerable to oxidation and rancidity. But then he states that the Lyon Diet-Heart Trial was the most successful diet trial of all time. Yes, it was successful. Their intervention clearly prevented adverse events. But what was that intervention?

It seems the lead author of that study says his intervention involved canola oil. That's one of these dastardly omega-3 polyunsaturated fats. Shouldn't that have oxidized the LDL of the people in that trial? Shouldn't that intervention have caused heart attacks rather than prevented them? How did this study manage to become Stephan Guyenet's favorite diet trial if it contradicts his beliefs so directly?

Guyenet loves to rip on margarine. It is so easy to do, he says. But Lyon was a trial that emphasized the use of margarine.

In the Lyon trial, their successful diet approach relied upon highly oxidizable omega-3 polyunsaturated fatty acids in the form of canola margarine. This is one reference saying this. You can find others. Really, search it. It's just so easy!

The authors of Lyon said that only alpha-linolenic acid was significantly associated with an improved prognosis. What is alpha-linolenic acid? It's a polyunsaturated fatty acid, the most oxidizing of LDL in the study Guyenet was discussing.

So how did the Lyon trial manage to be so successful? As you see, the experimental group really hobbled their efforts by decreasing LDL-defending saturated fat and increasing LDL-corrupting omega-3 fats. Don't they know about the whole oxidation problem the media is ignoring? Their study also decreased cholesterol intake. But don't we need cholesterol? You get the idea. This trial was successful for very mainstream and very obvious reasons. They cut back on saturated fat.

Understand that total cholesterol was called a major independent predictor of the recurrence of heart attacks by the researchers who ran this trial, who may be a little bit better informed about this one than the broscientist blogosphere.

In order to believe that saturated fat is better than unsaturated fat, we must assume that atherosclerosis is really a disease caused by oxidation reactions, and these oxidation reactions are caused by polyunsaturated fats. Neither saturated fats nor unsaturated fats have any other properties worth talking about beside their potential for oxidation. The more polyunsaturated fats you consume, the more vulnerable you are to heart disease. All these are assumptions that we should not accept without looking at the evidence.

Before I talk about all that, though, the most basic assumption seems to be that it is an asset of saturated fats that they are resistant to oxidation. Don't believe it. Actually, it is this resistance to oxidation along with its stiffer structure that makes saturated fat such a difficult thing for your body to deal with. If saturated fatty acids aren't easily oxidized, that means they are not easily used for energy and other purposes. They tend to linger and cause trouble. The body treats them like foreign invaders.

Your gut microbes don't seem to be such big fans of saturated fats. This very recent study by Alcock and Franklin examined the interactions of various lipids with microbes and then assessed how they might affect the inflammatory response of the host of those microbes. You are a host of gut microbes so this applies to you. As you see here, saturated fats were generally found to be inflammatory, and unsaturated fats, particularly omega-3's ,were found to reduce inflammation. That contradicts the low-carb message.

Saturated fats also attract immune cells called monocytes. Monocytes are the cells that turn into macrophages before they suck up cholesterol and turn into the foam cells that you'll find in arterial plaque. This slide comes from the same study that Guyenet used to argue that saturated fats protect against oxidation. If this study says that saturated fats trigger the destructive immune response in heart disease, maybe this is not the best study for a saturated fat-loving blogger to use.

As I said, polyunsaturated fats were generally found to be anti-inflammatory in the gut, but the story with them is quite a bit more complicated than that. We need to look at the different manifestations of polyunsaturated fats and see what they do in different contexts.

For example, people have embraced the idea of supplementing with fish oil without adequate evidence of their benefit and without considering better alternatives to them. Usually fish oil supplements are marketed as a way to prevent problems you shouldn't need to worry about in the first place.

Before we proceed further, I want to remind you that I recommend the consumption of whole plant foods rather than refined oils, with the possible exception of algal oils for those who are concerned about specific essential fatty acids. I am not here to defend the usual refined oils that accompany cooking. However, the saturated fat apologists have tried to direct your attention away from saturated fat to anywhere else, and that is why they pretend to be so concerned about vegetable oils. They've made these oils into another scapegoat. Don't let them confuse you. Vegetable oils are comparatively innocent next to cholesterol and saturated fat. This video is here to help you stay clear on that.

I cannot imagine how a fair and rational person could embrace saturated fat and simultaneously oppose unsaturated vegetable fats. There is a huge amount of evidence against saturated fats, as you know now from my videos, but there is comparatively little out there that raises concerns about vegetable fats. They have something big in their favor that animal foods don't: they lower cholesterol, and that is far more relevant to heart disease than any alleged concerns about oxidation.

In this study that examined 1100 older Italians for plasma levels of various fatty acids, polyunsaturated fatty acids were associated with lesser amounts of inflammation using a range of biomarkers. Even the much maligned omega-6 fatty acids seemed to be anti-inflammatory. The authors of this one took a subtle jab at those who have sounded alarms over these oils. Their hypothesis didn't work here.

In interpreting their findings, the authors wondered if the typical chronic inflammatory state observed in older people might reflect a lack of polyunsaturated fatty acids in their diets.

How many times have you seen it claimed by the saturated fat promoters that coconut oil is good for you because it has antimicrobial properties?

Look at the research the diet-heart deniers use to claim this and you won't find any consideration for what effect coconut oil has within the context of normal human digestion. They don't have any science on this so there is reason to doubt their claims. Alcock and Franklin found that unsaturated fats tend to have greater anti-microbial properties than saturated fats. Saturated fats are more likely to feed harmful microbes. The host responds to this by activating an inflammatory response. I included that sentence on the right so that you can see that omega-6's were found to be more inflammatory than omega-3's in this paper. It seems the truth is that less stable fats cause less inflammation, and that doesn't match with what the saturated fat promoters say.

Another recent paper reported the results of a trial comparing omega-6's against saturated fats directly. Those vegetable oils reduced liver fat as well as cholesterol and triglycerides. Saturated fat raised insulin levels. The omega-6 fats did not promote inflammation or oxidative stress.

All this runs counter to low carber dogma. These researchers even suggested omega-6s might be anti-inflammatory.

How does an animal food pusher argue with such a direct refutation of his beliefs?

Chris Masterjohn tried to discredit this study because it calls into question everything he stands for. He wrote a lengthy blog post that seems to be a response to it if you only look at his title and intro. Mostly, however, he sidetracked at length, writing about his favorite cherry picked ancient studies instead. He finally got around to dealing with this actual study if you could bring yourself to read his blog that far. Saturated fat consumption may have increased liver fat in this trial, but it did not induce fatty liver, he observed. Saturated fat pushes you toward fatty liver, but in this trial, the researchers never actually induced fatty liver with it. How's that for an inspiring defense? It gets better than that. He then gets totally nutty. Please pause the video and read this. He is so simple minded, he thinks that within the homeostatic machine that is the human body, butter would make liver fat go up in a purely linear fashion. Meanwhile, vegetable oils would remove fat from the liver linearly until there would be negative liver fat. Therefore, this study wasn't legit, or something. What the hell is he talking about? How can you have negative liver fat? And what other complex natural systems could be described with perfectly linear regressions? This argument is juvenile. Even the best educated among the cholesterol deniers reason like children. Masterjohn apparently has no answer to that study, and his only defense against it is a long-winded attempt to distract us from it.

What about the assumption that oxidation is the primary mechanism that causes heart disease? This is a complicated and controversial issue. As I have shown you in a past video, oxidized LDL can have both pro-inflammatory effects and anti-inflammatory effects.

The complexities of oxidized LDL have not been sorted out, regardless of the how much certainty the bloggers seem to have about it.

What causes LDL oxidation? What does it mean for disease? Those who pretend to know the answers based on their simple nutritional beliefs only expose themselves to contradiction.

For example, when a meal containing oxidized linoleic acid was fed to normal people, no oxidized fatty acids were later detected in their LDL or HDL. Those oxidized fats were cleared from their circulation in 8 hours. On the other hand, when oxidized cholesterol was fed to them, it remained in the plasma for 72 hours, appearing in the VLDL, LDL, and HDL. In other words, oxidized cholesterol hung around to cause trouble at least nine times longer than oxidized linoleic acid.

Here's a similar finding in regard to eggs. Eggs do raise cholesterol, regardless of what some stubbornly believe, as you can plainly see here. And they cause LDL to be more vulnerable to uncontrolled oxidation reactions. If the confusionists really thought the oxidation of LDL was the central issue in heart disease, they would tell you to stop eating eggs. They don't, though, because their agenda means more to them than logical consistency or science.

If they cared about LDL oxidation, they would instead tell you to become a vegetarian. In this study comparing vegetarians to omnivores in Taiwan, the LDL of the omnivores were more prone to oxidation. You can be sure those Taiwanese vegetarians consumed more polyunsaturated fats and fewer saturated fats than the omnivores.

Here's another problem for the confusionists. Trans fats are bad for you, as I trust you will agree. Trans fats cause heart disease, right? Who would disagree with that? But in this study that looked for the effects of trans fats on inflammation and oxidation, no effects of trans fats were found. But shouldn't trans fats cause oxidation if oxidation is what causes heart disease? Or does this mean trans fats are safe after all? Of course not. It just means that some people are making too much of the oxidation argument.

In this prospective study, no evidence was found that biomarkers of oxidative stress predicted heart disease events. That's a problem for the oxidation hypothesis.

In this prospective study, coronary disease endpoints were compared to the concentrations of omega-6 fatty acids in 25 different studies. Lower omega-6 concentrations were associated with a higher risk of non-fatal events. Low carb dogma fails again.

You probably know that trials pitting saturated fats against polyunsaturated fats have consistently found that saturated fats raise the risk of coronary events. I won't make a big point of this here because this is common knowledge, but please realize how damaging this is to the low-carb argument against unsaturated fats. Watch my Oil-Based Nutrition videos for more on this.

Research in animals also contradicts the simple claims of the saturated fat apologists. In this recent study, mice that were genetically vulnerable to heart disease were in effect "pretreated" by diets either high in omega-6 fatty acids or high in monounsaturated fatty acids. The mice that were fed omega-6 fats had less plaque. They even had less plaque after they were switched back to a pro-atherogenic diet high in saturated fat and cholesterol. The authors thought that exposure to omega-6 fats may have somehow primed their defenses by causing some oxidative stress. Who knows if that's what happened? The bottom line is that omega-6's were protective against heart disease here.

In this study on rats which looked at the effects of 32 different oils and fats, a cholesterol-raising saturated fatty acid, myristic acid, was found to contribute the most to the formation of clots in arteries. The omega-6 fatty acid linoleic acid was found to be the most protective against blockages. Again, the low carbers are totally contradicted by the evidence.

When do you hear the inconsistencies in the oxidized LDL hypothesis acknowledged by the broscientists and low carbers? Do you think they are even aware of them? For example, do you think they know that LDL cholesterol does not need to be oxidized in order for it to be taken up in foam cells?

This paper demonstrated that native LDLs can wind up in foam cells as well.

The first lipids to take root in early arterial plaques are not oxidized.

Advanced plaque formations called atheromas hold high levels of antioxidants like vitamin E and vitamin C.

When biomarkers of oxidation are found, they may even reflect an improvement in the condition of the arteries.

If you would like to read more about these contradictions, this article delves into all this and more. You'll see there is a lot the confusionists aren't telling you.

One of the weirder arguments against polyunsaturated fats is that the advanced plaques in atherosclerosis called atheromas are mostly filled with unsaturated fats. This one seems too crazy to merit much attention from me, but then, most of the low carb claims seem crazy to me so I may as well talk about this one, too. Here you see the Weston Price Foundation founders, Sally Fallon and Mary Enig, together making this claim.

Anyone who has seen an atheroma should realize that this doesn't quite ring true, as the lipid filled core is not fluid like polyunsaturated oils but is rather stiff and waxy instead. We should all know already that these plaques are filled with cholesterol. What are they talking about?

Upon what basis do they claim that atheromas are filled with unsaturated fats? They reference an old study authored by Carl Felton to make this claim. The low carbers love the really old research because their views are bound to the ignorance of the past.

If a saturated fat apologist were to read this study, one cause for alarm for him or her should be that the co-author of it is Michael Oliver. As I have shown you earlier in this video series, Michael Oliver had been one of the most famous cholesterol skeptics. But only one year after this paper was published...

He cited the Los Angeles Veterans Study as evidence in support of the lipid hypothesis. The LA Veterans study was a diet trial that fed men more unsaturated fats and less saturated fats, which prevented heart disease events.

Notice as well that this same study by Felton and Oliver also raised concerns about omega-3 fatty acids and the monounsaturated fat in olive oil. The latter, oleic acid, may be overlooked as a possible promoter of heart disease. I'll return to that.

These same authors later published another paper about the atheromas that develop during heart disease. This paper focused on the ones that were the least stable. Notice here please that cholesterol and cholesterol esters were said to comprise 77 percent of the lipids in the plaques. Yes, you heard that right. Most of the lipids in atheromas are not unsaturated vegetable oils. It turns out that atheromas are made up of – big surprise – cholesterol. Felton and Oliver reported that as atheromas become more filled with cholesterol and cholesterol esters, they become less stable and therefore more dangerous. Here is the point where the saturated fat-defending ladies should have figured all this out. They should have connected the dots. The polyunsaturated fatty acids in the plaques were there in the form of cholesterol esters.

I've shown this table before. It agrees with the finding in that paper. Most of the lipids in advanced plaques are cholesterol.

Here's another study that broke down the fatty acid contents of plaques. The most severe plaques were here, too, found to be mostly cholesterol and cholesterol esters.

This study found that atheromas "showed a vast accumulation of lipid, especially cholesterol, in comparison to normal aorta." This paper has also been cited by confused people as one of those that showed that linoleate, which you would associate with vegetable oils, was more abundant in severe plaques. You can see how some misunderstanding might arise from all this. Low-fat diet promoters fall into this trap, too. Look closely at the second line of this slide. It says, "the atheroma samples contained a larger proportion of linoleate relative to oleate than the normal aorta." The suggestion seems to be that these are free polyunsaturated fatty acids but that is not the case. Look at the body of the study and it is clear that this is a reference to cholesteryl linoleate, a cholesterol ester. Remember, saturated fats are harmful in part because they cause the body to synthesize more cholesterol. Polyunsaturated oils do not cause the body to synthesize more cholesterol. This is the bottom line. I added a little extra information to this slide to point out that there are oxidation products of linoleate that do correspond with disease.

However, how it got there and what it’s doing are not simple questions to sort out. Linoleate is from plants. Humans cannot make it and that is why it is considered an essential fatty acid. But it does not follow from all this that it causes plaque or increases the production of cholesterol, and it certainly doesn't make up most of the fats in the plaque. Consider this. Do you remember how I showed you that severe plaques contain vitamins E and C? Would you assume then that that means those vitamins cause heart disease? Probably not. You should hold off on blaming linoleic acid, too. The development of plaques is a complicated process and it would be foolish to assume that everything found in an atheroma caused it to develop.

Beside, there are other studies showing that plaques contain higher proportions of saturated fatty acids. Different plaques have different fatty acid compositions. This study found that the plaques found in internal thoracic arteries were filled with saturated fats.

Here, both saturated fatty acids and omega-6 fatty acids were found to be common in patients with coronary disease.

In those older studies, we should also consider the possibility that that linoleic acid got there through the dietary sources that you might not have considered. For example, people used to consume a lot of trans fats. Trans isomers of linoleic acid were later identified in plaques. I see no evidence that the researchers who wrote those old papers considered trans fats separately. There is no mention of them in the paper Sally Fallon and Mary Enig found. In this study, one of the trans fats found in plaques was conjugated linoleic acid. I talked about this in my Primitive Nutrition Series. This trans fat could well have come from dairy fat or other animal fats.

Rather than trying to pretend you can easily unravel all the complexities of the composition of plaques, you should focus on what is known through nutrition science. Trans fats are bad. You can't get them from whole plant foods. You can certainly consume them through animal foods. Various saturated fatty acids are associated with the progression of plaques. Polyunsaturated fatty acids are not. Anyone who ignores or tries to obscure these basic facts by sidetracking about arterial plaque composition either doesn't know what they don't know or they are trying to baffle you with BS.

The lipids in your body are not static. They are constantly undergoing change. Unraveling the complexities of the lipidome is at the cutting edge of today's biomedical research.

The lipidome is enormously complex and I frankly don't think anyone has a handle on it.

Your gut microbes can even synthesize fatty acids that promote heart disease.

Most of the dietary fatty acids can be synthesized within the body, so it doesn't make sense to conclude that a particular fatty acid in a plaque first came into the body through food.

For example, in this study, it was found that plasma monounsaturated fat concentrations did not track with the consumption of monounsaturated fats. They instead reflected saturated fat intake.

The most contemporary research into the effects of all these fats on atherosclerosis still places the focus of concern squarely on LDL cholesterol, and that is increased by dietary cholesterol and saturated fat. There is no research that I have seen that challenges the lipid hypothesis and what it means for nutrition. You may have noticed that the research the cholesterol deniers use is mostly quite old.

Something that seems to be lost on the proponents of saturated fat when they carry on about LDL oxidation is that it is generally believed that the oxidation that is observed in heart disease takes place within the plaque, not in the blood. When LDLs oxidize in the blood, they usually don't hang around very long. Those that remain are associated with disease.

It is now the consensus view that most of the oxidation of LDL happens within the artery wall.

Now, I would like to return to the topic of oleic acid, the fatty acid we associate with monounsaturated fats like olive oil. The body can produce this, as we just saw. Low fat diets may also promote the synthesis of oleic acid. This is not a bad thing as a low-fat diet that does not contain excess calories will not cause the accumulation of any fat in excess.

However, refined oils that contain oleic acid may not be as healthy as you think. Quoting this paper, "Oleic acid is the preferred substrate for cholesteryl ester formation. Increasing cholesteryl ester content of aortic tissue with age and atherogenesis is well known." This is where the problem with oleic acid comes in. LDLs that contain a higher proportion of cholesterol esters from oleate are especially dangerous.

An enzyme called ACAT produces this cholesteryl oleate. This paper argues that LDLs enriched in cholesteryl oleate are especially atherogenic. I won't run through all the evidence these authors present.

An experiment in African green monkeys brought attention to this issue. Since then, studies in humans have indicated that people without heart disease have more cholesterol esters from linoleate...

Whereas a positive correlation between cholesteryl oleate and atherosclerosis has been demonstrated among people with preclinical heart disease.

This makes sense because LDLs that are especially rich in oleate are more likely to attach to the artery wall. LDL particles with more cholesteryl linoleate are thought to be less atherogenic. Does this mean that monounsaturated fats in the diet promote heart disease? I don't think the answer to that is clear, but at this time it seems to me that the cautious approach is to avoid refined monounsaturated oils like olive oil, as they have very little nutritional value and a lot of calories...

And the consumption of these oils is associated with a greater presence of cholesteryl oleate. The risk/benefit balance seems to argue against olive oil at this time.

There are other uncomfortable facts about fats out there for the low carbers to grapple with. For example, the ketogenic diets they think are so great increase the endogenous production of polyunsaturated fatty acids. That's a bit ironic, isn't it? Going low-carb all the way means you produce more of your own easily oxidized polyunsaturated fatty acids. Some researchers think these polyunsaturated fats account for the calming of the seizures of epileptic children who are fed ketogenic diets.

Along with all those polyunsaturated fatty acids that ketogenic diets produce come all the downsides of these diets, like more of the inflammatory hormone cortisol, and side effects like lethargy, vomiting, anorexia, and bruising, in addition to the chronic and disturbing elevations in cholesterol levels that I have shown you in a past video. Children should not have high cholesterol.

The effects of the substitution of stable saturated fats with easily oxidized polyunsaturated fats has been observed through epidemiology. This excellent study out of Harvard examined the drop in heart disease mortality in former Eastern Bloc countries that occurred during the 1990s. During that time, butter and other animal fats lost their government subsidies and became more expensive. People started to consume more polyunsaturated oils. This paper found that increased alpha-linolenic acid consumption related best to their improvement in coronary death rates. That's a polyunsaturated fat.

Here is a graphic from an older study in Poland which should make this clear for you. When butter consumption dropped and vegetable fat consumption rose there, heart disease mortality plummeted for both men and women. The low carbers' beliefs about polyunsaturated fats are contradicted by reality.

So far only one aspiring Paleo broscientist has been openly critical of the content of my videos. He is not worth my trouble, but I have made a short video in reply to his ridiculous blog posts anyway.