What Is “Hyeolnok”? The Real Meaning of “Rusty Blood Vessels”

You may have heard the word "hyeolnok" on health shows or in ads. Hyeolnok is a commonly used short form of "blood vessels rust." It is not a scientific term found in medical textbooks. It compares the damage that happens in blood vessels when high blood glucose keeps recurring to iron rusting.

Three real changes the metaphor refers to

• Reduced endothelial function — The inner wall of a blood vessel is covered by a single layer of cells (the endothelium). When a lot of blood flows through, signals from the endothelium widen the vessel, and this refers to that response becoming dull. In hospitals, it is measured with a test called flow-mediated dilation, using ultrasound of the arm artery.
• Advanced glycation end products — Substances formed when proteins or fats stick to sugar. When they build up in the vessel wall, they stiffen the wall's structure, switch on inflammation signals, and produce reactive oxygen.
• Oxidative stress — A state in which too much reactive oxygen is produced in the body. Professor Brownlee of the Albert Einstein College of Medicine in the U.S. proposed a model in which the several pathways by which high blood glucose damages blood vessels all start from the excessive production of reactive oxygen in the cell's power plants (mitochondria).

Why post-meal blood glucose is discussed alongside it

Endothelial function also changes during the few hours when blood glucose rises after a meal. In a study by a Kumamoto University team in Japan that measured the arm artery response after participants drank glucose, people with normal glucose handling had a reduced response after 1 hour that nearly recovered by 2 hours. By contrast, people with impaired glucose tolerance (prediabetes) or type 2 diabetes had a larger drop in response and slower recovery.

That is why people say that when talking about blood vessel health, you should look at post-meal blood glucose as well as the fasting glucose number.

What to remember when you hear the word "hyeolnok"

• It is not a diagnosis. There is no official test called a "hyeolnok test." If you are worried about the condition of your blood vessels, blood pressure, blood glucose, and lipid tests and a talk with your health care provider are the place to start.
• Saying the rust can be "scraped off" is an exaggeration. Be careful with food ads that flatly claim to reverse blood vessel damage.
• The basics of management are the same. Body weight, physical activity, diet, not smoking, and regular checkups.