Linoleic Acid Stars as the Culprit in a Radicle New Outlook on Heart and Chronic Disease

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Story at a glance…

  • Many different foods and nutrients have been suggested as the cause of the growth in chronic disease in America.

  • There have always been exceptions to this demonization, whether of carbs, red meat, or fats, within certain world populations.

  • Industrial seed and vegetable oils, and the polyunsaturated fats they contain, appear to be the most likely candidate, for many different reasons, for America’s disease epidemics.

Over the 20th century, rates of chronic disease, cardiometabolic disorders, and heart disease grew in America in such a way as to bring a number of potential culprits onto the front page of scientific journal and tabloid magazine alike. Butter, saturated fats, red meat, cholesterol, simple carbs, sugar, and refined grains have all taken their turn in the hot seat of scientific and popular scrutiny.

However there is always a population somewhere on earth, whether the Japanese, the Inuit, or the French, that has thrown a wrench into the process by consuming a diet full of whatever it was in vogue to scrutinize. The most recent culprit is unique in that it’s also one of the most recently-added nutrients to the human diet—industrial seed or vegetable oils, like linseed, canola, sunflower seed, rapeseed, etc., and specifically a kind of polyunsaturated fatty acid (PUFA) therein called linoleic acid.

This is for two reasons. The first has been figured out in bits and pieces since the 1950s, while the other is a much more recent hypothesis.

The data are compelling since they implicate other known risk factors such as cholesterol, and strike down many other hypotheses that would necessitate implicating the diets of ancestral peoples like the Inuit or Hadza.

Furthermore, their supposed innocence has led to some large entities like the American Heart Association or the FDA recommending increased consumption of linoleic acid, the latter requiring their presence in baby food, while the vast livestock herds most industrialized nations draw their meat from are fed diets containing high amounts of corn and soy, creating a lipid profile containing 10-times more linoleic acid than the animals would contain naturally as grazers.

Further still, since these seed oils represent an enormous savings compared to using oils derived from oily foods like coconut, avocado, and olive, they quickly grew to occupy most processed foods. Linoleic acid is even sold as a dietary and workout supplement, and is used as a base for other supplements like royal jelly or ginseng.

All these aspects mean that the modern food system is soaked in industrial seed oils, even though it was once considered toxic industrial waste, and its presence in human fat cells has increased 136% over the last half-century. Any health implications derived from their consumption, one would think, should be treated with the utmost urgency. Some researchers like functional medicine pioneer Chris Kresser MD, have been ringing alarm bells on this topic for several years now, and his case is long, detailed, well-cited, and compelling.

PICTURED: A visual representation of atherosclerosis. Photo credit: Oregon State University. CC 2.0.
PICTURED: A visual representation of atherosclerosis. Photo credit: Oregon State University. CC 2.0.

Linoleic acid and atherosclerosis

Atherosclerosis is the term for cholesterol or fats forming plaques inside arteries, narrowing blood flow and causing blood clots. A large systemic review of the literature accompanied by a historical examination presented by researchers at Saint Luke’s Mid-America Heart Institute in Kansas City in 2018, outlined the potential danger omega-6 PUFAs pose to Americans through the well-recognized demon of LDL, or ‘bad’ cholesterol.

It bears explaining that most fish oil supplements market themselves as omega 3 and omega 6 fatty acids, when the more important designation is EPA and DHA. Linoleic acid is also an omega-6 fatty acid, but could also be the ingredient that causes 1 of 4 deaths in the U.S. every year, so it’s a distinction that’s worth knowing.

In the 1980s, they write, the oxidized LDL hypothesis for atherosclerosis gained traction as it was observed that unoxidized LDL particles didn’t cause plaque buildup on the artery walls. Accompanied citations state that oxidized LDL was higher in people with cardiovascular disease, along with being straight toxic in the cell membrane.

It was later discovered that oxidization of LDL was initiated by linoleic acids within the LDL particle itself, and future discoveries also concluded that the most numerous oxidized fatty acid within LDL was indeed linoleic acid.

The authors conclude their historical recounting thusly.

Hence, the amount of linoleic acid contained in LDL can be seen as the true ‘culprit’ that initiates the process of oxLDL formation as it is the linoleic acid that is highly susceptible to oxidation. Additionally, an increase in the intake of linoleic acid increases the linoleic acid content of very-low-density lipoprotein (VLDL) and high-density lipoprotein (HDL) increasing their susceptibility to oxidize, which further increases the risk of cardiovascular disease.

Thus, expanding on the oxLDL theory of heart disease, a more comprehensive theory, the ‘oxidized linoleic acid theory of coronary heart disease’, is as follows: dietary linoleic acid, especially when consumed from refined omega-6 vegetable oils, gets incorporated into all blood lipoproteins (such as LDL, VLDL and HDL) increasing the susceptibility of all lipoproteins to oxidize and hence increases cardiovascular risk.

One of the reasons this was overlooked in its day is simply because the buck ended up stopping with LDL and saturated fat, another compound present inside LDL. Yet LDL loaded with saturated fat doesn’t readily oxidize as it does with linoleic acid.

Lastly, when LDL oxidizes, linoleic acid is converted to hydroperoxides and then to hydroxy acids. Different hydroxy acids provide very consistent measurements for cardiovascular disease risk, even in healthy patients, going all the way back to the 1950s.

A radicle theory

Some scientists are positing the idea that linoleic acid’s entry into the cells disrupts the signaling pathway of hydrogen peroxide. Not only used by our grandmothers to clean cuts, hydrogen peroxide is produced as a natural byproduct of metabolism, and has been adapted by our biology to use as a signaling molecule.

Speaking with Dr. Anthony Gustin, an expert in linoleic acid and its effects, food historian Brad Marshall explains that as hydrogen peroxide interferes with cellular communications, resulting in insulin resistance, linoleic acid and alpha-linoleic acid prevent shifts towards insulin resistance, as was found in mice.

While it’s a scientific given that insulin resistance is a major contributor to chronic disease, Marshall explains that if the cells in your skeletal muscle are sensitive to receiving insulin signals, they will continuously absorb glucose and fat, creating new fat cells, even in a state of satiety.

This led Marshall to hypothesize that if laboratory mice were able to remain healthy on what was essentially a diet “consisting of a croissant recipe,” he would be able to as well. Therefore he launched the “Croissant Diet” and ate buttery croissant sandwiches all day for several months, losing about 16 pounds in the process.

As it was a 2-hour radio broadcast, Gustin remarked that there are few researchers acting on these data points now, but that the full spectrum of linoleic acid effects hasn’t even been established yet.

It’s strange to think how many American grandfathers or great aunts and uncles have died of complications from heart disease, diabetes, or stroke, and that decades later we still aren’t sure what’s doing it to us. Well just maybe, we’re finally on the right track. WaL

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