The human body has two different types of Blood Vessels, the Arteries, which carry oxygen-rich blood from the heart to the rest of the body, and the Veins, which return the oxygen-depleted blood from the body back to the heart. Vascular Disease is a condition whereby the Blood Vessels do not work properly to carry the blood. When Vascular Disease occurs in the arteries of the Heart, the more specific term, "Coronary Artery Disease," may be used. When Vascular Disease occurs in the arteries of the periphery (arms and legs), the term "Peripheral Artery Disease" is often used. Two major factors that cause Vascular Disease are Atherosclerosis and Endothelial Dysfunction.
Atherosclerosis is the process in which cholesterol is laid down inside the wall of an Artery. In the top left corner of the figure, a cross-section of a normal artery is shown, with blood (pink) flowing through it. The inner surface of the artery wall has a lining layer, called an endothelium (white), which is similar to the lining on the inside of your cheek. The bulk of the artery wall is made up of muscle (orange), which can tighten or relax as needed under different conditions.
In the upper right corner of the figure, an atherosclerotic artery is shown. A layer of cholesterol (yellow), inside the wall of the artery, leaves less room for blood to flow through the artery. Over time, more cholesterol may be laid down, making the open area of the artery smaller, until it eventually closes off. If this happens, or if a small blood clot gets stuck in a narrowed atherosclerotic artery, then the area of the body supplied by the artery may die. This can happen in a toe (Peripheral Artery Disease), in the Heart (Coronary Artery Disease), in the Brain (Carotid Stenosis, Cerebral Vascular Disease), or elsewhere. When this happens, it is usually painful, and it is usually life-threatening (or limb-threatening).
Endothelial Dysfunction is a condition in which an Artery does not constrict and dilate properly. Under normal conditions, the muscle in an artery wall has some tone, as shown in the top left corner of the figure (orange layer). The muscle tone keeps the artery at a certain diameter, allowing a normal amount of blood to flow through it at a normal rate. When required, however, a normal artery can dilate to supply larger amounts of blood to a tissue at a high rate.
A tissue under stress (such as your legs working hard during a bike ride) has a greater-than-usual need for oxygen-rich blood. During such periods of increased need, a stressed tissue (eg your legs) sends out chemical signals into the blood. In a normal artery, these chemical signals are picked up by the endothelium, which then directs the muscle in the Artery wall to relax. This in turn opens up (or dilates) the blood vessel, increasing its diameter, allowing more blood to flow to the tissue at a faster rate, as shown in the bottom left corner of the figure. When the stress is over, the chemical signaling stops, and the artery returns to its normal size.
If an Artery's endothelium is damaged, it may fail to pick up and pass on the chemical signals which are in the blood during periods of stress. In that case, the vessel will not dilate, and the needed increase in blood flow to the stressed tissue will not occur. This situation, shown in the right half of the figure, is known as Endothelial Dysfunction .
There are certain things that are known to cause Atherosclerosis and Endothelial Dysfunction. They include High Blood Pressure, High Blood Sugar (in Diabetics), High Cholesterol, Toxins from Cigarettes, and High Homocysteine (a chemical made by the body). There are other things that are known to repair endothelium and remove cholesterol from inside arterial walls. They include Exercise, Normal Blood Pressure, Low Cholesterol, and a vitamin called Folic Acid (which lowers Homocysteine).
Vascular Disease is very common in the United States. This is because most Americans eat a high fat diet and get little exercise. To my knowledge, the only people who have truly normal cholesterol levels (about 110 without medication) are (1) Athletes and (2) older generations of Japanese, who eat mostly fish, vegetables, and rice. Younger Japanese, who tend to eat American foods, have the same higher cholesterol levels as Americans. Another reason for the large amount of Vascular Disease in the United States is the number of Americans who smoke cigarettes. Smoking causes direct damage to blood vessels on a daily basis.
Folic Acid, or Folate, is an important tool in the prevention and treatment of Vascular Disease. It is a harmless vitamin that has no side effects. Most Americans should take a Folic Acid supplement every day. Generic brands of Folic Acid, in doses of 400 and 800 micrograms, are available in Drug Stores and at Wal-Mart for $2-3 per bottle. If you take a multivitamin with 400 micrograms of Folic Acid in it, that is probably adequate, but you must check to see that it has 400 micrograms, because some multivitamins have much less. If you buy Folic Acid separately, get the 800 microgram pills. (Prescription strength is 1000 micrograms.)
To maintain healthy Blood Vessels, it is also helpful to eat fish (bony fish - not shellfish) at least twice a week. Your Blood Pressure, Cholesterol, and Blood Sugar can be checked by your doctor. All three can be lowered with exercise. Additional information is available in the Exercise and Smoking sections of this web site.