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One Doctor's Journey to Viscosity

I am an internal medicine physician who has been practicing hospitalist medicine for 5 years now. I have been interested in nutrition and alternative medicine ever since meeting my wife during medical school who is a naturopathic doctor.

One night while listening to the documentary Forks Over Knives, one of the physicians interviewed in the documentary commented as an aside that a vegetarian diet likely helped decrease blood pressure by decreasing the thickness or viscosity of the blood. That statement hit me like a bolt of lightning.

I had been taught all of the leading theories that may explain hypertension, and blood viscosity was not one of them. Yet this theory, unlike the others, made perfect intuitive sense. There is clearly an environmental component to high blood pressure, which has been going up dramatically in the past few decades and is almost unheard of in primitive cultures, so I found the link between hypertension and hyperviscosity to be such a simple and elegant idea, like all great scientific hypotheses.

Viscosity and Blood Pressure

A stimulus from the environment or diet interacted with a genetic predisposition to lead to thick, high viscous blood. The body naturally would compensate by increasing blood pressure through constriction of blood vessels and increased heart contractility in order to keep blood flow constant and nutrient delivery to the tissues at its needed rate. It was powerfully simple and explained so many unanswered questions.

Just like any good internist I immediately dove into the literature to read about what research had been done. My first instinct was that this theory could not possibly be true or else would already be common knowledge. It seemed too simple and far-reaching to not be discussed in medical training and practice. But the more I researched the more backing for this idea I found. There were studies dating back to the 1980’s showing a clear association of viscosity and high blood pressure. Then I came across an even bigger and more revolutionary idea—that viscosity is the underlying cause of atherosclerosis.

This I could not believe. Could it be true that we had been ignoring the most important cardiovascular risk factor of all? The only one that is truly directly related to the formation of atherosclerosis?

Viscosity and Atherosclerosis

Again, I went to the literature to test this broader hypothesis using an array of questions. If elevated blood viscosity was the underlying cause of atherosclerosis, that would mean viscosity would have to be increased by tobacco smoking. It is—by about 20%. Then diabetes would also have to increase viscosity. It does. LDL cholesterol would have to increase viscosity. It does. HDL cholesterol would have to somehow decrease viscosity. It does. Viscosity would have to be elevated in those with atherosclerosis with no other known risk factors. It is.

Time and time again I went to the literature to test the predictions made by this theory, and every time the predictions were confirmed by studies.

I went to my colleagues to explain what I was finding. A few were interested. Most dismissed it with the same skepticism I had started with feeling that such a far-reaching, important idea could never have been missed by the myriad of brilliant researchers working on cardiovascular disease. But the data was there, and not one of my colleagues could give me a single good reason why this theory is wrong.

Slowly the realization came to me that almost the entire medical community (me included) with few exceptions had been studying what goes on in blood and arteries in ever increasing detail and complexity while ignoring the basic elephant in the room, the thickness of the blood itself and therefore how well it is flowing. Such a basic and powerful concept of human physiology was going mostly ignored except for a small core group of researchers who simply were not getting the attention they deserved from the greater medical community.

Viscosity Therapies

My research went on, and I began to investigate treatments. If viscosity causes atherosclerosis, what do we do about it? I soon found out from the literature that we have been treating viscosity all along. We just haven't been measuring it. Study after study showed that many drugs we use that have proven heart attack and stroke prevention capabilities decrease blood viscosity. Statins, fibrates, clopidogrel and many more were already proven to decrease blood viscosity. The beneficial lifestyle changes that have been shown to decrease stroke and heart attack risk such as vegetarian diet and exercise also decrease viscosity.

The more I researched the more it seemed clear; I had been treating blood viscosity as a doctor for years, I just didn't know it. I could count on the fingers on one hand how many times I had checked blood viscosity in a patient. My colleagues were no different. In fact many asked me if we could check viscosity at our hospital. We can, and it costs $7 to test blood viscosity. I started to use this test in practice, and it has lived up to the research.


One patient in his 50’s came in with chest pain with no known medical history. Turns out he had a heart attack, and when we checked his coronary vessels they were all close to complete obstruction. Only treatment in this case would be a bypass surgery, but his atherosclerosis was so bad even this could not be done. He essentially had no options.

I thought to myself, if this patient is going home with his vessels blocked to this degree he’d better have low viscosity blood or it simply won't flow. Also, for him to have atherosclerosis this severe, if the theory is true, his viscosity should be sky high. Indeed it was, 5.5, well above the upper limits of normal.

Another similar patient in his 40’s had a viscosity of 4.7. Yet another patient was on dialysis, had Crohn's disease and is frequently in and out of the hospital with infections but has zero atherosclerosis on all the scans we had done on her. So I checked her viscosity and it was 3, well within the normal limits.

Ever since, I have been researching blood viscosity and trying to see how I may help to spread awareness and get studies done. At times I have wished for someone to prove the theory wrong, so that I can put it down, relieved of the burden of feeling the need to spread awareness for this life-saving idea. But it hasn't happened. I have discussed it with many researchers and offered it to the editorial boards of major medical journals, and no one has been able to show any flaw in the logic or problem with the research done so far. They just want more studies. And so do I. Desperately.

I now wonder what other conditions high viscosity may cause or contribute to. Chronic fatigue syndrome?  Cancer?  Alzheimer's? We have no idea because this powerful and yet basic and foundational property of blood has gone mostly ignored. Checking and managing blood viscosity will almost certainly be transformative to the practice of medicine. It is time we start. We need to get our patients' blood flowing again.

Dr. Erik Finlayson M.D. is a hospitalist in Irvine, California specializing in the care of hospitalized patients. 


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