Good Fats Bad Fats : Are Polyunsaturated Vegetable Oils Healthy?


Refined commercial polyunsaturated vegetable oils are highly inflammatory to the body. Excess consumption can lead to heart disease, cancer and weight gain.

Drop into your local grocery store or supermarket, and you will see an array of polyunsaturated vegetable oils on the shelves. Corn oil, Sunflower oil, Safflower oil, Canola oil, Rapeseed oil, Soybean oil… All attractively packaged in clear plastic bottles, their golden glow promising health, and reduced risk of coronary heart disease.

A Mayo Clinic analysis of autopsy results between 1981 and 2004 suggests incidence of coronary disease may be rising. Of course, other factors may play a role but it is reasonable to question why the increased use of vegetable oils has not seen a corresponding drop in coronary disease.

Analysis of Polyunsaturated Vegetable Oils

Polyunsaturated vegetable oils contain omega-3 and omega-6 essential fatty acids. However, the commercial refined vegetable oils contain mostly omega-6 fatty acids and little omega-3. Nutritionist Patrick Holford and renowned authority on fats, Mary Enig Ph.D.,say for optimal health, your diet should contain roughly twice the amount of Omega-6 EFA as omega-3. Today’s modern diet contains about 20 times omega-6 as omega-3. Enig says the imbalance disrupts production of prostaglandins which can lead to increased incidence of blood clots, inflammation, high blood pressure, weight gain, cancer and depressed immune function.

Processing Polyunsaturated Vegetable Oils

Vegetable oils are extracted from oil seeds in a process, which involves high temperatures up to 180 degrees and the use of solvents and chemicals such as hexane, (derived from crude petroleum oil) sodium hydroxide, (caustic soda) and soda ash. (sodium carbonate) The oils are also bleached and deodorized.

The refining process not only adds dangerous substances to the oil, but also damages the fats. Mary Enig says the high temperature process disrupts the molecular structure of polyunsaturated oils and creates harmful disease forming free radicals.

Polyunsaturated Vegetable Oils: Health Issues and Research

A study reported in the April 1991 issue of the American Journal of Clinical Nutrition found that excess amounts of omega-6 polyunsaturated fats in the diet may lead to greater incidence of cancer.

A Study reported in the March 1971 issue of the British medical journal, the Lancet, showed a greater incidence of death from cancer by men on a diet high in polyunsaturated vegetable oils.

In a 1977 report in the New England Journal of Medicine, George Mann MD, questions why 25 years of a scientifically and medically recommended diet, replacing saturated fat with polyunsaturates, had shown no reduction in the rate of coronary heart disease.

A study by CV Felton, PhD., reported in the October 1994 issue of the Lancet shows most of the arterial placque, which leads to artherosclerosis and heart disease is made up of polyunsaturated fat. Interestingly. saturated fat is not a factor.

Enig says that vegetable oils are more toxic when heated—when you cook with them. They release cell destroying free radicals.

A study by a plastic surgeon found women who ate a diet high in polyunsaturated fats had more wrinkles than those who ate saturated fats.

One question has to be asked.

If there is such a body of evidence suggesting polyunsaturated vegetable oils are harmful to health, why does conventional medical and dietary advice continue to advocate consumption of these highy refined oils?


  • The Oiling of America : Mary Enig PhD., and Sally Fallon
  • Medical News Today : Heart Disease May be on the Rise According to Mayo Clinic Population Research.
  • Second Opinions: Polyunsaturated Oils Increase Cancer Risk
  • The New England Journal of Medicine: September 1977: Die-Heart :End of an Era
  • The Lancet: March 1971: Incidence of Cancer in Men on a Diet High in Polyunsaturated Fat.
  • The Lancet: October 1994: Diet Polyunsaturated fatty acids and composition of human aortic plaque


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