TRUTHITION

Polyunsaturated Fatty Acids: The Real Killer II

Polyunsaturated fat intake may be a contributor to the prevailing chronic disease pandemic.

January 19, 2025 Truthition Team

Introduction

In the previous article in this series, it was established that the scientific consensus for the causes of chronic diseases must be inherently flawed. It is paradoxical to posit that saturated fats, sodium, refined sugar, and physical inactivity have been directly causing the exponential increase in chronic diseases over recent decades when these assumed “causes” are all declining in parallel to the rise in chronic diseases. In contrast, a recently substantial introduction to the human diet, polyunsaturated fatty acids (PUFAs), appear to correlate strongly with the rise in chronic disease. This article will delve deeper into how vegetable oils—and by extension, PUFAs—are causing chronic disease, and expand on the foods to avoid eating and their healthier substitutes.

Heating The Skillet

Modern scientific consensus agrees that unsaturated oils, when heated at a temperature too high and/or for too long, become rancid and toxic to consume. There have been several negative health effects attributed to consuming foods with heated vegetable oils, such as French fries, fried chicken, and potato chips, linking their consumption to CVD (cardiovascular disease), atherosclerosis, and numerous cancers.

A review paper on heated oils published in Vascular Pharmacology in 2014 states that heated oils have been associated with endothelial (blood cell wall) dysfunction and hypertension (read our article on blood pressure here). Furthermore, an excess of free radicals in the body, a phenomenon known as oxidative stress, has been linked to intake of these heated oils.^[11] These particles not only negatively affect the body on a macro scale, causing cell wall blockage, but can also interact with even smaller particles, like DNA. Damage to the DNA is an established cause of cancer, as the cell’s DNA self-correction no longer functions properly.

There are several chemical processes that occur upon cooking oils which result in the release of various toxic fumes. A review on reheated oils in Food Science and Nutrition found that carcinogens were released into the air; the fumes being related to “genotoxic, mutagenic and carcinogenic activities.” ^[12] The review also cited several other studies which found that deep-frying fumes increased rates of lung cancer and various other cancers in the subjects who inhaled them. If merely breathing in the fumes from heated oils is toxic, it can be inferred that consuming the heated oils is substantially worse.

Animal Fat or Plant Fat

Perhaps it is known that heating these vegetable oils is bad, but the intrinsic health differences between vegetable oils and animal fat oils are clear. Regarding cooking in general—not just frying—a 2023 study published in Current Problems in Cardiology Vol. 48 analyzed the link between the consumption of vegetable/sesame oil, lard/animal fat, and atherosclerotic cardiovascular disease (ASCVD). ASCVD is a term for health issues that result from the buildup of cholesterol and other substances accumulating in the artery walls. This accumulation causes numerous health issues and is associated with high mortality rates.

The study found that vegetable and sesame cooking oil intake was linked with significantly higher rates of ASCVD than cooking with lard and animal fat in general: approximately a 31.68% prevalence in vegetable oil consumers versus the 17.46% in animal fat consumers.^[13] Remarkably, vegetable oil consumers also had a lower prevalence of smoking and drinking and exercised significantly more often. Despite this, they had a higher prevalence of ASCVD as well as greater overweight, obesity, and high blood pressure rates. Animal fat consumers also ate fewer vegetables, consumed more alcohol, smoked more often, and exercised far less. Despite this, vegetable oil consumption was correlated with several diseases, begging the question: why?

Perhaps it’s the chemical composition of the oil itself, or something wrong with how the plants were grown in this region (as the study’s subjects were exclusively Chinese elders), which may be a fair argument. However, there is a far stronger argument to be made that the dominant fatty acids in vegetable oils—polyunsaturated fats—are at the root of the problem.

A 2013 meta-analysis published in The BMJ found contradicting results to the scientific consensus that polyunsaturated fats are conducive to cardiovascular health. Over 450 men with a recent coronary event were prescribed to replace dietary saturated fats with omega-6 linoleic acid (a type of polyunsaturated fat, known as an “essential” fatty acid). The group with PUFAs as the primary source of fat in their diet had a mortality rate of 17.6%, approximately 1.67x higher than the 11.8% mortality rate of the non-intervention group. Similarly, the PUFA group had a cardiovascular disease rate of 17%, while the non-intervention group had a rate of 11%.^[14]

This study suggests that the medical recommendations to replace saturated fatty acids (SFA) with omega-6 linoleic acid PUFA are not conducive to cardiovascular health by any measure. For reference, vegetable oils are generally high in omega-6 and very low in omega-3, which may lead some to the premature conclusion that omega-3s are safe, even if omega-6s are not; however, it appears that even omega-3s are not as healthy as medical consensus claims.

A Cochrane study found that there was little to no benefit for an increase in omega-3 consumption. The 2018 systemic review found that there was little to no benefit of this increase in all-cause mortality, cardiovascular mortality, or CHD (coronary heart disease) events. The authors concluded that ALA omega-3 may slightly reduce risk of cardiovascular events, but the probability went from 4.8% to 4.7% upon intervention and was not statistically significant.^[15] Overall, there was no probable benefit from supplementing or increasing omega-3 intake in this large-scale meta-analysis, especially from high-quality studies.

Different Types of Fats

There are a few basic distinctions to make between different types of fats in the human diet. To begin with, there are saturated fatty acids, polyunsaturated fatty acids, and monounsaturated fatty acids (MUFAs). All fats are made up of carbon, hydrogen, and oxygen atoms. Without getting too deep into the chemistry, carbon and hydrogen make up much of the fatty acid, with oxygen usually at one end. The distinction between saturated fats and polyunsaturated fats is established by the fact that saturated fatty acids have a straight bond between the carbon and hydrogen molecules, as it is saturated with hydrogen molecules. It can be thought of as a more “rigid” fat, and it is far more chemically stable in high temperatures than polyunsaturated fats. In polyunsaturated fats, there are multiple (poly) parts of the overall structure that have double bonds between carbon atoms where there are no hydrogen atoms (unsaturated). This makes polyunsaturated fats much more unstable than saturated fats and therefore far more prone to oxidation.^[16] In monounsaturated fatty acids, there is only one (mono) double bond, placing it in between saturated and polyunsaturated fats.

PUFAs can be further divided into subcategories of omega-3, omega-6, and omega-9 fats. Omega-3 and omega-6 are considered “essential fatty acids” as the human body cannot produce them. However, the human body is capable of producing omega-9 fatty acids. These fatty acids are classified by how far the first double bond is from the methyl end (the end opposite of the oxygen atoms). For example, if the first double bond is at position 3 from the methyl end, then it is classified as an omega-3 fatty acid. The same logic follows for 6 and 9. They are general classifiers for the types of PUFA.

Omega-3s include:^[16]

• Alpha-linolenic acid (ALA)

• Eicosapentaenoic acid (EPA)

• Docosahexaenoic acid (DHA)

Common omega-6s include:^[16]

• Linoleic acid (LA)

• Gamma-linolenic acid (GLA)

• Arachidonic acid (AA).

An example of MUFA is:^[16]

• Oleic acid (OA)

SFAs include:^[16]

• Stearic acid (C18)

• Myristic acid (C14)

• Palmitic acid (C16)

• Butyric acid (C4)

PUFA, MUFA, or SFA?

Each type of fat plays its own role in the diet. How each fat is processed is also quite important to how it should be consumed. Throughout human history, saturated fats were far more prevalent than polyunsaturated fats. Meat, milk, cream, butter, and other dietary sources outweighed nuts, seeds, and fatty fish in terms of calorie intake. MUFAs have also been around, especially in the form of olive oil. However, the primary source of polyunsaturated fat has changed in the last century from nuts, seeds, and fatty fish to vegetable oils such as canola, sunflower, grape seed, and soybean oil.

These oils are processed, sometimes hydrogenated (meaning the double bonds are packed with hydrogen), and found in exponentially higher quantities in the human diet than ever before. To illustrate, by consuming 2 tbsp of grape seed oil, you are consuming the equivalent of approximately ¼ lb of grape seeds.^[17] Given that about 5% of the weight of a grape is its seed,^[18] that is equivalent to consuming the number of seeds found in 4-5 pounds of grapes. Considering that a single grape with seeds is about 7.35g, that is approximately 250-310 grapes.

It goes without saying that number is far greater than the number of grapes any human would eat in one day, both as hunter-gatherers and in modern industrial societies. The point being made here is that these new and processed oils are far more concentrated sources of polyunsaturated fats than have ever been available before throughout human history. The fatty acid composition of grape seed oil is approximately 71% PUFA.^[16]

Another oil source throughout history that is more accessible now is olive oil. Specifically, those with olive oil as the primary fat source in their diet have decreased mortality rates and decreased cognitive decline associated with aging.^[19] Olive oil has a far lower PUFA content, at about 11%, compared to its 73% MUFA content.

In a 2009 publication of Lipids, a study conducted on rats compared the effects of different lipid compositions and found that there was a 15.82% increase in phosphatidylcholine in interstitial cells (cells in-between tissue).^[20] As a precursor to the micronutrient choline, phosphatidylcholine is known for its numerous health benefits such as improved brain function, as well as being a common treatment option for fatty liver disease.^[21,22]

Perhaps the most striking benefit of this study in particular is the correlation found between testosterone and different types of oils. Among others, there are two key enzymes in testosterone production: 3b-hydroxysteroid dehydrogenase and 17b-hydroxysteroid dehydrogenase, or 3bHSD and 17bHSD for short. In the study, olive oil and coconut oil (MUFA-rich and SFA-rich, respectively) had much greater activity of these enzymes compared to either soybean oil or grapeseed oil (PUFA-rich), therefore leading to overall higher levels of testosterone.^[20]

What’s next?

The analysis of the studies given has revealed that diets high in monounsaturated fats (MUFA) and saturated fats (SFA) provide superior health outcomes compared to diets high in polyunsaturated fats (PUFAs). However, more research is needed to fully understand why PUFAs may not be the healthiest option. Part 3 of this series will delve deeper into the biochemical factors that contribute to the potentially negative health effects of PUFAs. It will expand into the deeper aspects of PUFA and its biochemistry, looking at its influences on inflammation, cancer and sunburn, and more.

Citations

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