The Scary Facts About Polyunsaturated Fats 

The Scary Facts About Polyunsaturated Fats 

In This Article

Vegetable Oils

pouring oil

In the 1960s, heart disease was on the rise and researchers blamed saturated fats or cholesterol on the new epidemic. Since that time, any food, activity, nutrient or substance that lowered cholesterol was automatically deemed beneficial for heart disease. Vegetable oils – more specifically omega-6 polyunsaturated fats – were found to lower cholesterol levels and were, therefore, deemed good for your heart.

Not so fast! The premise that cholesterol caused heart disease has been challenged in study after study (1,2), but to this day, we are still being prescribed statins, eating certain polyunsaturated fatty acids (PUFAs) which were the replacement fats for cholesterol, and avoiding saturated fats (like butter) in an effort to lower cholesterol.

Many of these cholesterol-lowering foods, oils and drugs that are still in common practice today in the name of good health are under intense scrutiny. Some experts suggest that many vegetable oils may actually increase the risk of heart disease and mortality, instead of lowering it. (2,3)

Should We Stop Eating Cholesterol-Lowering Foods?

In this article, I will discuss the potential health risks of ingesting omega-6 polyunsaturated fatty acids (PUFAs) or vegetable oils that take up an entire aisle in grocery stores. These vegetable oils are used to extend the shelf life of packaged foods and are found in almost every loaf of bread, cracker, chip, bar, candy, nut milk, meat substitute, frozen meal, salad dressing and packaged food.

In the 1960s, vegetable oils replaced saturated fats as heart-healthy alternatives, as they were shown to lower total cholesterol levels. For decades, the consensus was that anything that lowered cholesterol was considered “heart-healthy.” (1) Recent studies have poked serious flaws in this theory. In a handful of studies, omega-6-rich vegetable oils lowered cholesterol levels, but they failed to lower the risk of heart disease or heart disease-related death – suggesting that lowering cholesterol may not protect your heart. (3)

In one study, a diet rich in saturated fats was replaced with a diet rich in omega-6 vegetable oils. While cholesterol levels dropped, the risk of death from all causes, heart disease and coronary artery disease risk increased. (3)

In the same report, researchers discussed how omega-3 fish oils – which are also polyunsaturated fats –have been found to raise cholesterol levels, but decrease the risk of cardiovascular events. To make this matter more confusing, there are studies suggesting that omega-6 vegetable oil fatty acids can lower the risk of cardiovascular events, rather than increase it. (7,8)

There are also studies that suggest omega-6 vegetable oils are pro-inflammatory and increase cancer risk. (9)

When omega-6 fats are ingested in combination with omega-3 fats, like those found in fish oils, the risk of cancers, particularly breast cancer, goes down. This suggests that it may be the lack of omega-3s in conjunction with excess omega-6s that may be the culprit. (10)

Understanding Vegetable Oil Risk

Vegetable oils, such as canola, soy, sunflower, corn, grapeseed, safflower, rice bran, cottonseed oil and, of course, those fake butter spreads like margarine are all rich in omega-6 polyunsaturated fatty acids.

Polyunsaturated fats (PUFAs) are long strands of fatty acids that are vulnerable to being broken and, therefore, oxidized. They are more vulnerable than saturated fatty acids like butter because they have two or more double bonds – thus the name, “poly” unsaturated fatty acid. Saturated fats have no double bonds, making them more stable and more solid at room temperature.

The more double bonds the fatty acid has, the more likely it will be susceptible to attack by an oxygen molecule. Once oxygen infiltrates the fatty acid chain, the fatty acid becomes damaged or oxidized, rendering that fatty acid a toxin rather than a nutrient.

In fact, many researchers believe it is not the omega-6 fats or vegetable oils that are the problem, and rather the fact that they are easily and commonly damaged through oxidation. (3)

When these oils are heated, as in cooking, frying or processing, the double bonds easily break and a cascade of oxidation ensues, causing severe free radical damage. In nature, the seeds from which these vegetable oils are made are very temperature sensitive. In the winter, the cold keeps the seed dormant and the oils safe from oxidation. Come spring, with warmer temperatures, these PUFAs are released to support germination. To ensure the seeds do not prematurely oxidize, the seed is rich in protective antioxidants to ensure the germination process is complete. It is like nature’s starter fluid that initiates plant growth.

Processing Problems

Any excess heat, which happens during pressing the oils (even during expeller pressing) will damage these delicate PUFAs. Expeller pressed only means that the manufacturer did not use toxic solvents like hexane to extract the oil. The refined, bleached, deodorized and boiled vegetable oils that line the grocery store shelves have had any viable nutrients or antioxidants stripped out, rendering these oils toxic and incredibly difficult, if not impossible, to digest. (4,5)

Even organic, expeller pressed oils have been found to have mutated, oxidized, heat-damaged oils in them. (4) In one study, expeller pressed canola oil was found to have 5% trans fats (linked to heart disease), cyclic hydrocarbons (a carcinogen) and oxyphytosterols (linked to arterial damage). (4)

The worse news is that when we ingest trans fats found in vegetable oils, they destroy the good fats in our bodies at a whopping rate of billions per second (5), in a process called “free-radical cascade.”

So… maybe it’s time to throw out all of the clear vegetable oils you have in your pantry.

Fried Food

Heating these PUFAs, as I mentioned, only accelerates the free radical cascade of damage and oxidation in the body. In a famous New Zealand study, researchers evaluated the blood flow through the arteries after a fried food meal. They used a blood pressure cuff to see how fast the blood vessels would dilate back to normal after ingestion of a meal cooked in used, fast food fryer oil.

The results were dramatic. Four hours after ingesting the meal cooked in one-week-old vegetable oil, they measured how quickly the artery would recover from the pressure of the blood pressure cuff. Before the meal, the vessels dilated normally, but afterward, there was almost no dilation! (5,6)


  1. Avoid Using Vegetable Oils At Home

Sadly, because these oils are used in almost every restaurant, if you eat out regularly, you are likely ingesting too many omega-6 vegetable oils. The refining, bleaching, boiling and deodorizing during the manufacturing process strips all of the nutrients and natural antioxidants from them, while severely damaging their structure.

Since these oils are so delicate, unstable and not a part of our ancestral diet, it makes good sense to avoid using them at home, at least.

  1. Replace Unstable Fats With Stable Fats

Vegetable oils that are more saturated will be more stable at room temperature and under high heat. The oils that are OK to cook with are: Butter, gheecoconut oil and macadamia oil. High-quality olive oils are OK at low heat or at room temperature.

When we think in terms of ancestral nutrition, a diet of saturated fats from organ meats, dairy and coconuts was common and easy to access. Taking the oil out of a vegetable seed only happened in our digestive tract. Extracting vegetable oil from a sunflower seed requires an enormous amount of pressure. Once the air and light hit these delicate oils, the risk of damage through oxidation is extremely high, which makes one wonder whether we were meant to eat only the seed rather than press the seed to extract the oil…

According to science, when it comes to fats, it is all about the rate of oxidation. Healthy people who have lots of naturally-occurring antioxidants in their blood and lymph and enjoy a properly balanced ratio of omega-6 fatty acids to omega-3 fatty acids seem to do fine, and there are even reported health benefits.

In smokers, the elderly, or folks in a weakened state with less natural antioxidant activity, the tendency for greater oxidation and damage to these omega-6 vegetable oils rises, along with associated health concerns.


  5. Shanahan, C. Deep Nutrition.228. Flatiron Books. NY pg. 139

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Dr. John

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