First of all, what exactly are seed oils?

Seed oils (also including vegetable oils) are oils that come from seeds and grains that have been heated to extremely high temperatures and are pressed under extreme pressure. To further extract as much oil as possible, petroleum solvents such as hexane are used. To remove the rancid smell and the grey color that these oils evolve then into, the oil is deodorized and bleached to render it odourless and visually appealing.

Some of the oils that I am talking about here include canola/rapeseed oil, soybean oil, corn oil, sunflower oil, grapeseed oil and safflower oil. Yes, these are the oils that are present in things that have been (and still are) marketed as being “heart healthy” ---this is why reading your labels and understanding the ingredients is so important. (If you want to know the history on why they are marketed this way and how they even ended up into our food system let me know and I can do a post on this!)

Seed oils are a concentrated form of omega-6 polyunsaturated fat (PUFA). There are 2 types of PUFAs, omega 6 and omega 3. Both omega 6 and omega 3 are considered essential fatty acids, meaning that the body needs these fatty acids for many body functions but are not produced endogenously (by the body) and need to be obtained from dietary sources.

Most of everything that is processed and packaged contains some form of seed oil (omega 6). These seed oils are often used as they are generally tasteless (due to the refining process) and they are cheap. Many restaurant kitchens cook with them for this reason as well.

Why is excess omega 6 oils in particular worrisome?

Omega 6 fats are in high in linoleic acid which is highly associated with the Western Diet. Research has shown us that consuming foods with omega 6 fats from whole foods (eggs, nuts, some greens, pork and chicken) in moderation can be beneficial for health, especially with adequate intake of omega 3 (EPA and DHA). Optimal dietary ratio of omega 6 to omega 3 fats is 1:1--4. Ancestrally, we were consuming about a 1:1 ratio, and had practically zero incidence of chronic disease. In our western diet, studies have shown that we are consuming around 10:1-20:1 omega 6 to omega 3 fatty acids. With this increase in this ratio, the incidence of chronic disease has dramatically increased. Increased omega 6 intake has been associated with virtually all inflammatory diseases including cardiovascular disease, autoimmune disease, inflammatory bowel disease, obesity and cancer. The mechanism behind this is their susceptibility to oxidization and the production of pro-inflammatory eicosanoids. [1]

First, let’s talk a bit about the oxidization potential of PUFAs. Due to the molecular structure of PUFAs and the extensive refining process the seed oils go through, they are already highly oxidized (rancid) sitting on the grocery store shelves in those clear plastic bottles even before they are heated on a hot pan or fryer and in your body. When these oils are used in cooking, this accelerates the oxidization process even more. Oxidization of linoleic acid can occur from exposure to air, heat, light and stomach acid [3,5].

What is Oxidization?

Oxidization basically means the loss of an electron which creates free radicals in the body. The way human biology and chemistry works, is that electrons always travel pairs. When this is disrupted, free radicals are formed which are very aggressive, reactive molecules which continue to steel electrons from neighboring molecules. This starts a chain reaction which continues to propagate until all neighboring cells are affected. The oxidization of these fats lead to the production of toxic chemicals such as aldehydes and lipid hydroperoxidases. Aldehydes are known substances found in cancer cells and lipid hydroperoxidases are responsible for the oxidation of cholesterol which leads to atherosclerosis (heart disease) [2,3].

Another way these oils are further oxidized is through enzymes (such as COX-1 and COX-2) that are induced by free radicals and lipopolysaccharide (which is an endotoxin that is released when damage has occurred to the intestinal wall) which lead to production of eicosanoids. Eicosanoids are biologically active lipids which stimulate production of prostaglandins and leukotrienes. Prostaglandins and leukotrienes are pro-inflammatory. Pro-inflammatory states are associated with increased oxidation, increased platelet aggregation (blood clotting), vasospasm and vasoconstriction, thereby increasing the risk of development of conditions associated with these mechanisms [2, 3].

Fun Fact: This is the mechanism behind why NSAIDs such as ibuprofen and naproxen work for pain and inflammation and why they contribute to gastric bleeding. They are known as COX-2inhibitors which block the inflammation and clotting process [4]

It’s important to note that omega 6 and omega 3 compete for the same conversion enzyme to make omega 6 arachidonic acid (precursor for eicosanoids) and omega 3 DHA and EPA (which are anti-inflammatory) . This conversion enzyme does favour omega 3, however, when there are elevated or more concentrated levels of omega 6 present, any fat, omega 3 or omega 6, will be converted into arachidonic acid [1]. For example, if you fry your fish in vegetable oil, the vegetable oil will win the war of enzymatic activity and will prevent your body from receiving the EPA/DHA from your fish. Cook your fish instead in ghee or butter! (More about saturated fats later..)

So, what do I do?

While supplementing with DHA/EPA and eating fatty fish at least once a week can be helpful to increase your omega 3 levels, if you are consuming omega 6’s in excess, your supplementation and diet efforts are going to waste.

1. First of all---cut out the seed oils! Replace them with oils such as olive, butter, tallow, ghee, lard, coconut and avocado oil. For high heat cooking, ghee, coconut and tallow are favorable over olive and butter. There is also a new company called “Zero Acre Farms” which has produced cultured monounsaturated oils which are heat-stable and have a neutral taste. Zero Acre Farms - Website

2. Read your labels! Most people are likely getting large amounts of omega 6 oils in salad dressings and in processed/packaged foods. Replace your salad dressings with a home-made dressing made with olive oil. Even if it says its “heart-healthy”—make that a clue to read the labels even more carefully. Often these foods contain at least some portion of seed or vegetable oil. I have also seen vegetable oils in things like seasoning mixtures and dried fruits (particularly raisins)! Always read your labels. There are brands such as “Primal Kitchen” which produce dressings and sauces which contain only monounsaturated fats such as olive or avocado oil. Primal Kitchen - Website

3. Also, supplement with high quality omega 3’s containing DHA and EPA and eat fatty fish at least a week. I will post on omega 3’s another time!

If you are interested to learn the mechanisms that seed oils lead to obesity in particular and why they were introduced into our food supply in the first place, please send us a message!

PMID: 22570770

References:

[1] PMID: 22570770

[2] PMID: 26950145

[3]Tao, L. (2015). Oxidation of polyunsaturated fatty acids and its impact on food quality and human health. Adv. Food Technol. Nutr. Sci, 1, 135-142.

[4] DOI: https://doi.org/10.1074/jbc.274.33.22903

[5] PMID: 31739445

Tao, L. (2015). Oxidation of polyunsaturated fatty acids and its impact on food quality and human health. Adv. Food Technol. Nutr. Sci, 1, 135-142.