GOOD & BAD CHOLESTEROL: PART 1
Why do we measure cholesterol?
IN this article, I’m going to cover some information about cholesterol tests. Many of us have gone to our local doctor and had a regular cholesterol blood test or a ‘lipid profile’. Generally, the test is done after you’ve been fasting and usually eight hours is the appropriate time, more than about 12 or 14 hours is too long as sometimes the body can change its metabolizing and this causes changes to the profile. A phlebotomist takes the blood sample and sends it off to the lab for analysis. So, what do we test when we’re looking at a lipid profile or a cholesterol test? There’s generally a panel of things and a number of different components to the test.
1. Total Cholesterol.
The first thing that we evaluate is the total cholesterol, which measures all the cholesterol within the blood. There is a range as you might imagine for total cholesterol, but the average is somewhere around 5 or 5.5 mmols per liter.
2. Triglycerides.
Once we’ve looked at the total cholesterol, the next thing to look at is triglycerides. They are another form of fats that are within the bloodstream. They are the most abundant of the lipids and are important for transport of fat into and out of tissues, so are a good indicator of what fat may be available to be deposited into the tissues. That spare tyre around the tummy is thanks to triglyceride deposition. With triglycerides, levels in the blood stream of less than about 2 mmols per litre are good. If they’re greater than 2 mmols per litre, there’s a good chance you’ve eaten or drunk (alcohol) a little bit too much recently. We also see those
levels elevated in a diabetic patient or someone at risk of diabetes in the future, if you carry a too much weight particularly around the middle.
3. High Density Lipoprotein - HDL.
HDL cholesterol is the more dense lipoprotein particle that can pick up cholesterol from the tissues and bring it back to the liver or deliver cholesterol to the tissues that produce hormones. This cholesterol is a protective or good cholesterol. So, when it comes to HDL cholesterol, we would ideally want to see it over 1mmol per litre.
4. Low Density Lipoprotein - LDL.
LDL cholesterol or low-density lipoprotein is the problem cholesterol. This is because a lot of our research has pointed to this being linked to development of plaque in the arteries and so has been the target of cholesterol lowering therapies.
WHAT IS THE ROLE OF CHOLESTEROL IN CORONARY ARTERY DISEASE?
In recent years, in the popular press and in social media, there is often some debate about the role of cholesterol in coronary artery disease. If your cholesterol level is high, that does not mean that you will have plaque in your arteries. There are people with high cholesterol levels who never have heart problems, while some with average cholesterol levels end up with coronary artery disease. However, studies have shown that in high risk individuals, lowering their LDL cholesterol offers a favorable outcome compared to placebo or doing nothing. So, the take home message is that cholesterol levels are not a good predictor of WHO will have plaque in the arteries but if you HAVE plaque in your arteries, then lowering cholesterol will be of benefit. The conclusion to Good & Bad Cholesterol: Part 2, is in the following article in this issue.
Dr Warrick Bishop is a cardiologist with special interest in cardiovascular disease prevention incorporating imaging, lipids and lifestyle. He is author of the book ‘Have You Planned Your Heart Attack?’, written for patients and doctors about how to live intentionally to reduce cardiovascular risk and save lives! Dr Bishop can be contacted via his website.