Does High Cholesterol Cause High Blood Pressure?

For most of us, our first experience with chronic illness is high blood pressure. Hypertension does not respect healthy lifestyles. Even people who maintain normal weight, exercise regularly, maintain healthy cholesterol levels, and eat a heart-healthy diet can be and frequently are diagnosed with the condition. In the United States, nine out of ten people will develop hypertension by the age of 60, and six out of ten eventually take high blood pressure medication.

If blood pressure readings are consistently higher than 160/110, doctors usually insist on prescription medication. But when blood pressure is between 120 and 160 systolic (the pressure generated when the heart beats) or between 80 and 94 diastolic (the pressure when the heart is at rest), the diagnosis is “borderline hypertension.” This condition of slightly elevated blood pressure can be treated with medication just to lower the numbers, or it can be treated with nutrition to correct its underlying causes.

Borderline hypertension is usually “essential” or “primary,” meaning it is not associated with an abnormality in a specific organ. Until a few years ago, the causes of essential hypertension eluded medical science, but recent research has revealed that this nearly universal health problem begins as with cholesterol—but not high cholesterol.

The human body produces two principal forms of cholesterol, bulky, low-density particles of cholesterol known as low-density lipoprotein, or LDL, and compact, high-density particles of cholesterol known as high-density lipoprotein, or HDL. LDL cholesterol is typically termed “bad” and HDL cholesterol is typically termed “good,” but actually both forms are necessary for the body. The larger LDL particles serve as a food for some of the body’s largest cells, the immune system’s macrophages, the cells that surround and engulf foreign and microorganisms (as well as LDL cholesterol itself).

The cholesterol particles are used by every cell in the body to make their protective linings, serving as “rain slicker” keeping their contents from dissolving in the watery bloodstream. Since they do not dissolve in water, they have to be attached to a transporter protein, apo-B. This protein has regions of positive and negative charge that allow it both to carry cholesterol and to be carried in the watery serum of the bloodstream.

For the bulky LDL cholesterol to be processed by cells, it has to be transported through the cell membrane. The cell membrane has to “unhook” LDL from apo-B and release the carrier protein back into the bloodstream. The detachment of LDL from its carrier molecule requires energy. If the cell is metabolically depleted by too much sodium, it cannot produce the energy it needs to bring LDL inside. On a tired cell, LDL parks on the outside of the cell.
The relatively bulky molecule of LDL in limbo on the surface of the cell is particularly vulnerable to attack by free radicals of oxygen. Without adequate levels of antioxidant free radical quenchers such as vitamin E, LDL cholesterol combines with oxygen to form lysophosphatidylcholine, better known by its acronym LPC. This chemical is the primary component of artery-hardening oxycholesterol, thickening artery walls and encouraging inflammation.

In people with normal blood pressure, oxycholesterol does not get a chance to damage arteries. A balanced immune system produces antibodies to LPC that keep it from accumulating in the linings of blood vessels. Antibodies to LPC perform the immune system’s equivalent of a surgical strike, dissolving the oxidized cholesterol before it can form artery-clogging plaques. In people with borderline high blood pressure, however, the immune system fails to produce the antibodies that clean up LPC. Their immune systems are forced to use the immune system’s equivalent of a battering ram, the macrophages.

These “cholesterol gobblers” surround and engulf LPC but become stuck in the intima, the inner lining of the artery wall. The intima slowly thickens and squeezes the artery so that blood pressure slowly increases. It is important to understand that the immune deficiencies that cause borderline high blood pressure do not affect the immune system as a whole. Only the antibodies to oxidized cholesterol are out of balance.

It’s also important to understand that everyone does not react to either high cholesterol or high sodium by developing high blood pressure. Combinations of factors, of which cholesterol and sodium are only the major part, determine the condition.