Difference between "GOOD" and "BAD" Cholesterol; Why Cholesterol only tells us part of the story.

Whether you come to me or another Los Angeles cardiologist, you will usually have a series of blood tests to diagnose existing cardiac problems or predict cardiovascular disease risk. We have been told for the past 50+ years that cholesterol is the enemy and that we should avoid it in food wherever possible. But our bodies produce cholesterol from various glycerol esters of fatty acids (triglycerides); sometimes the amount produced is excessive.

Today we recognize that measuring total cholesterol is not sufficient to maintain good health and forestall future cardiovascular problems. Enter HDL and LDL, which most people are told by their doctors are “good” and “bad” cholesterol, respectively. Generally speaking, we see patients being told to raise their HDL levels and lower their LDL levels. However, people should always remember that HDL and LDL are NOT actually cholesterol but lipoproteins containing cholesterol. HDL is high-density lipoprotein and LDL is likewise low-density lipoprotein. These lipoproteins contain a fair amount of cholesterol, but what are the other components present?

Lipoproteins Mean Lipid Transport

• It’s easiest to think of lipoproteins as lipid transporters.
• LDL particles each contain a molecule of apolipoprotein B (Apo B) along with a fair amount of cholesterol (the cholesterol inside LDL particles is called LDL-C).
• Their function is to transport lipids from the liver to other target tissues in the body, which include the insides of arteries.

We know that high LDL levels are not good. But what about people who have normal LDL-C levels and still develop cardiovascular events (heart attacks and strokes)? In many of these cases, even though LDL-C is normal, the number of LDL particles (LDL-P) is abnormal. This means not only are there too many LDL particles, but the particles themselves are also small and dense instead of big and loose. But what about if LDL-C only appears normal, but really isn’t? In patients with high glucose and high triglyceride levels (common in metabolic syndrome, a.k.a insulin resistance), LDL-C levels appear to be low, but because of the glucose and TG levels, the measurement is inaccurate! So by performing an LPP (lipoprotein particle profile) test, we can see things that LDL-C alone cannot reveal.

HDL is made up of Apo A-I and Apo A-II (plus cholesterol, triglycerides, etc.). HDL transports lipids OUT of target tissues and routes them back to the liver, where the cholesterol is broken down. That’s why HDL-C is considered to be “good cholesterol.”

We can also test for Apo B in the blood in addition to LDL-P. Remember, these are not standard tests that are readily available in the office of your average Beverly Hills cardiologist. We offer them because they provide our patients with just another of many powerful tools we employ in our proactive, preventive cardiology approach. Now since LDL particles always contain one molecule of Apo B apiece, you might think the two tests are equivalent. Not exactly, because Apo B also is present in other non-HDL particles besides LDL, such as VLDL (very low-density lipoproteins). So by measuring Apo B levels as well as LDL-P levels (and looking at size and shape of the LDL particles), we can get a very good idea of your cardiovascular risk.