Cholesterol – the good and the bad
Your liver has produced most of the cholesterol in your blood, although some does come from the foods that you eat. Cholesterol is carried in your bloodstream by lipoproteins. There are two important cholesterol-carrying lipoproteins in the blood.
The Good (HDL-C)
High-density lipoprotein cholesterol (HDL-C) normally makes up about 20-30 % of the total cholesterol carried in the blood. High-density lipoproteins (HDL) pick up choles- terol from the walls of the arteries and take it back to the liver for recycling or for excretion into bile. We call HDL the GOOD cholesterol carrier because the more HDL-C you have the more protected you are against the buildup of cholesterol in your arteries. If you have too low a level of HDL-C, there is a greater chance that cholesterol will build up in the walls of your arteries and lead to heart disease.
The Bad (LDL-C)
Low density lipoprotein cholesterol (LDL-C) usually makes up about 60-70 % of the total cholesterol carried in the blood. We call LDL-C the bad cholesterol carrier, because too much LDL-C can cause cholesterol to build up in the walls of your arteries. This build up is known as plaque and it causes thickening of the walls of the arteries (atherosclerosis). Over time, the cholesterol-rich plaque bulges into the lumen of the artery, accumulating more and more LDL-C. Eventually, the arteries become so narrowed that blood flow is slowed down or blocked. When this happens you may suffer angina (chest tightness or discomfort in your left arm or jaw due to poor blood flow in the heart muscle). If a cholesterol-rich plaque ruptures, the artery may become completely blocked by a blood clot and you may suffer a heart attack.
Remember: HDL = Healthy cholesterol, and LDL = Lousy cholesterol
Lowering LDL-C and/or raising HDL-C result(s) in a decrease in the cholesterol content of plaque, increased plaque stability and a reduced likelihood of plaque rupture. Overall, this reduces the risk for a heart attack. In addition, lowering LDL-C and raising HDL-C appears to improve the ability of blood vessels to dilate, improving blood flow to the heart.
If we subtract HDL-C from the total cholesterol we will have a measure of the amount of cholesterol carried by all the “bad” lipoproteins but not the “good” ones (which is only HDL). This measure is termed non-HDL cholesterol (non-HDL-C). Non-HDL-C is a better marker of risk of heart disease AND the best risk predictor of all cholesterol measures, both for heart attacks and for strokes.
High levels of blood triglycerides (TG), are also a risk factor for heart disease, particularly when non-HDL-C levels (total cholesterol – HDL-C) levels are elevated. Fasting blood triglyceride levels above 10 mmol/L increase your risk of pancreatitis (a serious inflammation of the pancreas). To avoid pancreatitis, severely elevated triglyceride levels require treatment even if you have no other risk factors for heart disease. Successful treatment requires optimal blood sugar control if you have diabetes, weight loss, alcohol and refined carbohydrate restriction and avoidance of oral estrogen and retinoids.
Lipoprotein(a) – also known as Lp(a) – is a cholesterol- carrying particle in your bloodstream that is genetically determined (inherited). High levels of Lp(a) promote cholesterol build-up in your arteries and interfere with the breakdown of blood clots (thrombolysis), which increases your risk of suffering a heart attack or stroke. Lp(a) levels greater than 30 mg/dl (300 mg/L) are associated with an increase in the risk of heart disease and stroke. The risk increases even more with levels above 50 mg/dl. Because Lp(a) levels are dependent on genetics, lifestyle changes have little effect on reducing Lp(a). Your Lp(a) measurement can help your doctor determine whether earlier treatment of other heart disease risk factors is indicated. An Lp(a) above 50 mg/dl may indicate that a LDL-C lowering drug is warranted even if you have a borderline elevation in LDL-C.