The Science Behind Blood Viscosity
The Science Behind Blood Viscosity
Clinical research has confirmed significant correlation between increased blood viscosity and atherosclerosis, myocardial infarction, peripheral artery disease, and stroke, as well as dementia, Alzheimer’s, angina, and heart arrhythmias (1).
By 1986, approximately 270 risk factors had been identified for developing atherosclerosis, many of which are modifiable such as blood pressure, dyslipidemia, smoking, diabetes, exercise, and obesity (2). Up to 90% of coronary heart disease could be prevented by optimization of known cardiovascular risk factors (2). Fixed risk factors include age and gender, but elevated blood viscosity is arguably the initiating mechanism from which all other risk factors contribute to the development of atherosclerosis (1).
What Is Blood Viscosity?
Show Section
Viscosity can be defined as a measure of a fluid’s resistance to flow, depending on the “thickness” of the fluid. Water has very low viscosity, whereas honey or oil has high viscosity. Adding particulate matter to the fluid only adds to the viscosity (1).
Blood contains many particles and nutrients that contribute to blood viscosity, including red blood cells, proteins, white blood cells, fatty acids, coagulation factors, electrolytes, lipoproteins, along with vitamins and trace elements. All of these contribute to blood viscosity in varying amounts and are modifiable.
The Shear Effect and Vessel Damage
Show Section
When particulates circulate immersed in a primary fluid, there is a shear effect, defined as a force applied parallel to the internal surfaces. The shear rate is calculated as the ratio of flow velocity to pipe diameter. As the shear rate increases, so does the shear stress on the walls of the pipe (1). Fortunately for human “pipes” or vessels, these walls can expand and contract to help mitigate some of this shear force.
As we age, however, the constant force of the shear rate causes increasing damage to the internal surface layers of our vessels. To repair the damage, the body “patches” these endothelial injuries with a combination of lipids, calcium, fibrin, and foam cells. These patches then harden the vessel wall to help compensate for the increased shear force. As more and more hardening takes place, blood pressure increases and ultimately shear force increases beyond physiological levels, and a rupture or thrombosis can occur. Viscosity is a direct measurement of the likelihood of one of these events.
Key Contributors to Blood Viscosity
Show Section
The most important contributor to high blood viscosity is dehydration. A lack of water content in the blood causes a higher concentration of particles, with a subsequent higher shear rate within the blood vessels. Hydration levels can be monitored by various means, including serum BUN/creatinine ratios (a high ratio indicates dehydration), and 24-hour urine output (optimal is 2000–2500 mL daily).
The second most important contributor to blood viscosity is red blood cell deformability. Most red blood cells have a lifespan of 3 to 4 months, and the “younger” the RBC, the more bendable it is in fitting through small capillaries, carrying oxygen to the tissues. Donating blood periodically is a way to keep RBC cells younger and more pliable. Blood donations have been shown to lower risk of heart attack by up to 88% (3), and other CV events were also reduced by 50% in non-smoking blood donors (4).
Nutrients and botanicals are also useful in alleviating increased blood viscosity, and will be presented in a subsequent article.
Who Should Consider Blood Viscosity Testing?
- Individuals with known cardiovascular risk factors such as hypertension, dyslipidemia, diabetes, or obesity.
- Those with a personal or family history of atherosclerosis, heart attack, stroke, or peripheral artery disease.
- Patients experiencing symptoms of poor circulation, angina, or unexplained fatigue.
- Anyone concerned about cognitive decline, dementia, or Alzheimer’s risk.
- People looking to proactively manage and reduce modifiable cardiovascular risk factors.
Testing with a licensed provider can help identify elevated viscosity early and guide targeted, evidence-based interventions.
Final Thoughts
Elevated blood viscosity is arguably the initiating mechanism behind many of the most serious cardiovascular and neurological conditions. Fortunately, many of the contributing factors are modifiable — from hydration and red blood cell health to targeted nutrition and lifestyle changes. Understanding and measuring blood viscosity is a powerful step toward protecting long-term cardiovascular health.
References
- Kensey K, Cho Y. The Origin of Atherosclerosis: What Really Initiates the Inflammatory Process. 2nd ed. SegMedica; 2007.
- Identification and relative weight of cardiovascular risk factors. Cardiol Clin. 1986 Feb;4(1):3–31. PMID: 3518932.
- Donation of blood is associated with reduced risk of myocardial infarction. The Kuopio Ischemic Heart Disease Risk Factor Study. Am J Epidemiol. 1998. PMID: 9737556.
- Possible association of a reduction in CV events with blood donation. Heart. 1997 Aug;78(2). PMID: 9326996.
