The Overlooked Blood Factor That Could Predict Heart Disease Years Before a Heart Attack

Blood viscosity, or how thick your blood is, may be a unifying factor behind many well-known cardiovascular risk factors like high cholesterol, diabetes, and high blood pressure. A new research review published in Microvascular Research suggests that measuring this simple characteristic could help doctors catch heart disease earlier and prevent devastating outcomes like heart attacks and strokes.

What Is Blood Viscosity and Why Does It Matter?

Most people focus on cholesterol numbers and blood pressure readings when thinking about heart health, but Dr. Erik Finlayson, a hospitalist at Mission Hospital in California, spent more than a decade exploring a different angle. His research review draws from over 40 years of existing studies to explain how blood thickness affects your cardiovascular system. When blood becomes too viscous, or thick, it moves more slowly through your arteries, placing stress on artery walls. Over time, this stress triggers inflammation and plaque buildup, especially in curved or branching arteries where heart disease commonly develops.

"Blood viscosity is something we have been able to measure for decades," said Dr. Finlayson. "The idea that paying attention to this simple factor could help us catch heart disease earlier and prevent devastating outcomes is what kept me motivated." His work suggests that measuring blood viscosity could one day become an additional tool for physicians to better assess risk and guide treatment.

Which Conditions Increase Blood Thickness?

Dr. Finlayson's research identifies multiple conditions and lifestyle factors that increase blood viscosity, creating a common pathway to cardiovascular problems. Understanding these connections could help people recognize their risk earlier:

• Smoking: Tobacco use increases blood thickness and reduces oxygen delivery to tissues.
• Diabetes: High blood sugar levels alter blood composition and increase viscosity over time.
• High Cholesterol: Excess cholesterol particles thicken the blood and promote plaque formation.
• Obesity: Excess weight increases inflammation and blood thickness throughout the body.
• COVID-19 Infection: The virus can cause lasting changes to blood properties and clotting risk.

The key insight is that these seemingly different conditions all share a common mechanism: they make blood thicker and harder to pump, forcing your heart to work harder and damaging artery walls in the process.

Can Medications Help Improve Blood Flow?

Dr. Finlayson's review also examined how common heart and diabetes medications affect blood viscosity. Some treatments improve blood flexibility in ways that may help protect against heart attacks and strokes, suggesting that medication effectiveness might partly depend on how well they reduce blood thickness. This finding could help doctors choose treatments more strategically based on a patient's individual blood viscosity profile.

What Does the Latest Research Say About Olive Oil and Heart Protection?

While blood viscosity represents one emerging approach to heart disease prevention, recent research also highlights the protective power of specific dietary compounds. High-phenolic olive oil—extra virgin olive oil with elevated levels of antioxidant and anti-inflammatory molecules—has emerged as a promising dietary intervention for cardiovascular health.

For years, scientists attributed olive oil's heart benefits to its unsaturated fats, but newer evidence points to polyphenolic molecules as the true protective agents. These potent compounds include tyrosol, hydroxytyrosol, oleocanthal, and oleacein. A five-year study conducted in Spain found that participants supplementing their diets with high-phenolic olive oil had significantly lower incidence of heart disease compared to those consuming regular olive oil.

One particularly important polyphenol is oleocanthal, an anti-inflammatory molecule. A 2017 study showed that people who consumed extra virgin olive oil with high amounts of oleocanthal displayed the lowest risk of platelet aggregation and blood vessel blockage—both critical factors in preventing heart attacks.

New 2026 clinical research presented in the European Heart Journal strengthens this case further. In a randomized, double-blind, placebo-controlled trial, participants with chronic coronary conditions who received olive-derived polyphenols showed significant improvements in vascular function, including better blood vessel performance and coronary blood flow, along with improved heart relaxation and reduced oxidative stress compared to placebo.

How Much High-Phenolic Olive Oil Do You Need?

Most studies showing cardiovascular benefits used about two tablespoons of high-phenolic olive oil per day, and this amount is enough to see positive effects. However, research suggests that more consumption may offer additional protection. The critical factor is quality over quantity—the higher the polyphenol concentration, the better. High-phenolic olive oils can contain up to 10 times more polyphenols than average olive oil, making them a more efficient choice if you're looking to maximize heart-protective benefits.

The research also shows that introducing high-phenolic olive oil into diets for just three weeks caused changes in genes known to be involved in blood pressure regulation, resulting in decreased blood pressure after the study period.

What's Next for Heart Disease Prevention?

Dr. Finlayson's work on blood viscosity and the emerging research on olive oil polyphenols represent two complementary approaches to understanding and preventing heart disease. Rather than relying on a single measurement or intervention, the future of cardiovascular health may involve a more nuanced understanding of how multiple factors—blood thickness, inflammation, cholesterol, and dietary compounds—work together to either protect or damage your heart and arteries. As these research areas continue to develop, patients and doctors may have new tools to catch heart disease risk earlier and intervene more effectively.