Traditionally, humans have always eaten fats and oils that were predominantly saturated and animal-based. Edible seed oils were introduced into our diets about a century ago and have taken over as our main source. They are made by crushing seeds like cotton, corn, soy, canola etcetera and industrially refining the oils. One of the first to be refined into oil was cottonseed. It was an agricultural byproduct with little value until it was realized that the oil contained in the seeds could be extracted and used industrially. In 1911, the oil was hydrogenated, and Crisco was introduced as a cheap lard substitute. (1) Over the next several decades, the new industrial seed oils replaced the traditional fats like butter, tallow, and lard. These oils contain large amounts of omega-6 oils which are problematic for our health. We utilize fats for a variety of uses including building blocks for cell membranes, and energy storage. This high omega-6 substitution has had a dramatic effect on our health which I will discuss a bit later.

Saturated Fats

Fats and oils are classified as saturated, mono-saturated and unsaturated. The more saturated an oil is, the more chemically stable it is. When a fat is saturated, all the carbons have the maximum number of hydrogens attached to them. When they are unsaturated, not every carbon is full of hydrogen atoms, causing an unstable double bond. This is why tallow can be left at room temperature for long periods without going rancid, while canola oil quickly goes rancid. (2) The term polyunsaturated means that there are multiple double bonds, making the oils even less stable. The unstable double bonds cause the fat molecules to react and become oxidized. Another name for oxidized fats is “Reactive Oxygen Species”, or ROS. Specifically, Lipid peroxidation is the correct term when referring to oxidized fats (lipids). Peroxidized lipids are so reactive that they start a chain reaction in the body whereby one oxidized fat can generate thousands of other ones. (3) Oxidized fats and oils are toxic, yet our metabolic systems cannot adequately rid of them and even incorporate them into our tissues and cells. (4)

Unsaturated Fats

Polyunsaturated fats are grouped into two main categories: omega-3 and omega-6. Both versions cannot be made by the body, therefore the only way we can be healthy is to include them in our diets. They are labeled as “essential oils” because of this. (5) Omega-3’s are considered the good ones and omega-6’s are bad, but this is only part of the story. (6) Optimal dietary intakes of the omega-6 : omega-3 ratio should be around 1–4 : 1. However, due to the increase in seed oils in the human diet, this ratio has now increased to be within the range of 10 : 1 to 20 : 1 (7) Increases in chronic inflammatory diseases such as nonalcoholic fatty liver disease (NAFLD), cardiovascular disease, obesity, inflammatory bowel disease (IBD), rheumatoid arthritis, and Alzheimer's disease (AD) cancer and others have been on the rise and parallel the increase in seed oil consumption. (8) The charts below show the increase in omega-6 consumption over time and the switch from infections to chronic inflammatory diseases over a similar period of time.

Chart of Fat Consumption Over Time (9)

Comparative Chart Of Causes of Death 1900 and 2010 (10)

* the heart disease in 1900 was from rheumatic heart disease and valvular problems

Below I briefly discuss 3 ways omega-6 fats can cause damage and disease.

Mechanism I

Eicosanoids are biologically active lipids and include prostaglandins, thromboxanes, leukotrienes, and hydroxyeicosatetraenoic acids which have all been implicated in various pathological processes such as inflammation and cancer (11) When they are comprised of omega-6 fats, they tend to promote inflammation, conversely (12), when they are made from omega-3’s they are anti-inflammatory. (13) Numerous studies demonstrate that inflammation is at the base of many diseases including non-alcoholic fatty liver disease, cardiovascular disease, atherosclerosis, irritable bowel disease, and Alzheimer’s among others. (14)

Mechanism II

Mitochondria are cell structures that generate energy in the form of ATP. A critical component of the process is cardiolipin which is made from fat. When it is made from an omega-6, oxidation chain reactions occur that damage the mitochondria and can even cause it to cease to function. (15) Mitochondrial dysfunction is a factor in Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, amyotrophic lateral sclerosis, and Friedreich’s ataxia; cardiovascular diseases, such as atherosclerosis and other heart and vascular conditions; diabetes and metabolic syndrome; autoimmune diseases, such as multiple sclerosis, systemic lupus erythematosus, and type 1 diabetes; neurobehavioral and psychiatric diseases, such as autism spectrum disorders, schizophrenia, and bipolar and mood disorders; gastrointestinal disorders; fatiguing illnesses, such as chronic fatigue syndrome and Gulf War illnesses; musculoskeletal diseases, such as fibromyalgia and skeletal muscle hypertrophy/atrophy; cancer; and chronic infections. (16)

ATP Production THrough the Electron Transport Chain In Mitochondria

Mechanism III

Omega-6’s causes the creation of acrolein, HNE, and MDA. Acrolein is the acute toxin to all life (it is also found in cigarette smoke). Acrolein is so toxic it can cause lung cancer in non-smokers. (17) HNE causes mitochondrial dysfunction, cell death, tissue death, and DNA damage. MDA and HNE kill living cells, cause mutations in DNA and destroy DNA. (18) It doesn’t get much worse than this folks!

Finally, I would like to mention Omega-6’s role in gum disease (periodontitis). Poor nutrition (high omega-6 consumption) has been implicated in several inflammatory diseases and conditions, including cardiovascular diseases, type 2 diabetes mellitus, rheumatoid arthritis, and inflammatory bowel disease, all of which have been associated with periodontitis (19). Iwasaki et. al. found that a high omega-6 to omega-3 ratio, but not total omega-6 intake, was significantly associated with a greater number of periodontal disease events in the elderly. Authors consider dietary omega-6 to omega-3 ratio as the main predictor to estimate influence on periodontal disease events (20). In one study in people, the omega-3 supplementation effect was investigated in the treatment of experimental gingivitis. Volunteers who were given fish oil showed a significant decrease in gum inflammation compared to controls( 21).

In Summary

Omega-6 oils have increased in our diets for the last century, displacing more stable saturated fats
Humans have tended towards diseases of inflammation over the last century in parallel with increased oega-6 intake
The ration of omega-6 to omega-3 should be below 4:1
The ratio is more important than the total amount
Omega-6 oils oxidize and cause us to generate less energy to thrive
Omega-6 oils oxidize and create toxins that make us sick
Omega-6 oils make our bodies skew towards an inflammatory state

If you are like most others in the modern world, you may have some issues from eating too much omega-3 oils. All is not lost; if you switch to a diet with the correct ratio below 4:1, in time your body will recover. It may take a few years, but worth the wait.

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The Hazards of Too Much Omega-6 Oils on our Health