The role of dietary polyunsaturated fats in heart disease and atherosclerosis

Townsend Letter for Doctors and Patients, August-Sept, 2003 by Wayne Martin

There was a trial in the USA again among doctors called the Physicians' Health Study. It was hailed as an astounding success of aspirin in the prevention of heart attacks. It was given as the reason why everyone over age 40 should be taking an aspirin a day to keep from having a heart attack. The results were reported in New England Journal of Medicine in the January 28, 1988 issue.

The results of this trial were not all that astounding. There was no reduction in fatal heart attacks and there was no increase in survival. Non-fatal heart attacks were reduced by 40% but Bufferin was used and Bufferin contains aspirin and some magnesium. The magnesium in Bufferin could have caused the good results in this trial such as they were.

The orthodox medical establishment is not given to reading medical journals and no attention is paid at all to Nobel Awards for Medicine. This was especially true of the 1982 Award.

The 1982 Nobel Award for Medicine was shared by Dr. John Vane, now Sir John, of the Wellcome Foundation and Dr. Bengt Samuelsson of the Karolinska Institute. Their discoveries were of epochal importance. Dr. Vane discovered what was first called prostaglandin X but is now called prostacyclin. He also told much about the arachidonic acid cascade. We get arachidonic acid, a polyunsaturated fatty acid, in meat. We can make just a little of it from the polyunsaturated fatty acid linoleic acid which we get much of in our diet.

Arachidonic Acid and Cyclo-Oxygenase

Arachidonic acid is acted on by the enzyme cyclo-oxygenase to form a series of prostaglandins or prostaglandin-like substances. Two of them are thromboxane A2 and prostacyclin. Prostaglandins are slightly oxidized arachidonic acid. Thromboxane A2 contributes to the adhesion of platelets causing a blood clot to form. This is good in a wound but bad in a coronary artery. Prostacyclin acts in just the opposite way--lowering the adhesion of platelets and preventing coronary blood clots.

Aspirin inhibits the enzyme cyclooxygenase, thus inhibiting the formation of thromboxane A2. This would tend to limit the amount of thromboxane A2 which might prevent a coronary blood clot and hence a heart attack. That is given as the reason for aspirin to prevent a heart attack. Dr. Vane has noted that aspirin also inhibits the highly beneficial prostacyclin. He predicted that the aspirin trials in the prevention of a heart attack were doomed to failure because the good done by the inhibition of thromboxane A2 was offset by the harm done by aspirin in the inhibition of greatly beneficial prostacyclin.

Moreover, he noted that to get beneficial prostacyclin, some antioxidants such as the tocopherols or vitamin E were needed, otherwise one will not have a slightly oxidized arachidonic acid to turn into beneficial prostacyclin, but one will have a greatly oxidized and harmful peroxide fat. He took note of the harm of adding a great amount of the polyunsaturated fats to diet from which the antioxidants had been removed.

We have reported on the harm done by adding to diet the new polyunsaturated fats. Now we will relate the great benefit of a small amount of one of the polyunsaturated fatty acids, gamma linolenic acid. This is the work of Dr. Samuelsson. Here is his teaching: we get plenty of the polyunsaturated fatty acid linoleic acid. Corn and sunflower seed oils are 50% linoleic acid. Linoleic acid is acted on by the enzyme delta-6-desaturase to form gamma linolenic acid. It is converted in the body to dihomo-gamma linolenic acid and then to prostaglandin El which has many benefits.