This post was written by Charles Presti, MD, PPG – Cardiology.
If you are reading this, you’re probably interested in the vital role that cholesterol plays in health and disease. Let’s get started by exploring what cholesterol is, its positive and negative properties, testing for it and actions you can take.
The skinny on cholesterol
Cholesterol is a waxy, fat-like substance that is present throughout the body. Despite all the bad press, cholesterol is an essential part of our existence. All animal cells need some cholesterol. It is an integral part of our cells’ structure and other important molecules such as vitamin D, hormones like estrogen, testosterone and cortisol, and bile acids that aid in digestion. Additionally, cholesterol plays an integral part in the structure and function of our nerve cells. The brain contains the most cholesterol of any organ in the body. The body gets this necessary cholesterol through two primary mechanisms:
- Liver: About 80% of the cholesterol in our body gets manufactured in the liver. The liver makes essentially all the cholesterol the body needs, which illustrates just how important cholesterol is for normal bodily functions.
- Diet: An additional 20% of cholesterol comes from our diet.
However, despite these critical roles, excess cholesterol in the bloodstream is a major contributor to atherosclerotic plaque development, which can lead to an increased risk of heart attack, stroke and peripheral artery disease. High cholesterol is one of the key risk factors, along with high blood pressure, diabetes and smoking that we can modify to help reduce our risk of developing blood vessel problems.
Testing
High cholesterol doesn’t cause symptoms until significant plaque has built up in the blood vessels, which may take many years. For this reason, it’s necessary to get your cholesterol checked earlier rather than later, so you can make changes, if necessary, to reduce the chance of build-up.
A simple blood test, also known as a lipid profile or panel, can easily do this. The American Heart Association recommends all adults over the age of 20 have their cholesterol checked every 4-6 years as long as their risk remains low. However, if you are at a higher risk due to other risk factors, such as vascular disease development or are taking medications to treat high cholesterol, you may need to have your lipids assessed more often.
Likewise, if there is a strong family history of vascular disease at a young age, you may need to have your lipids checked before 20 years old. This is due in part to the growing problem of childhood obesity and the potentially dangerous effects of a lifetime of exposure to high cholesterol levels. Therefore, the American Academy of Pediatrics recommends that children between the ages of 9 and 11 get a cholesterol screening.
Fasting
For many years an 8-12 hour fast was required before measuring a lipid profile in assessing cardiovascular risk. However, more recent evidence has shown that non-fasting lipid profiles provide equally accurate information for most people. Most lipid levels change only minimally in response to normal food intake. With that said, in some patients with high triglyceride levels or genetic lipid metabolism disorders, fasting samples may still be necessary. Non-fasting testing allows more flexibility and fewer office visits for patients. More importantly, recent studies have not demonstrated any substantial difference in non-fasting versus fasting samples’ predictive accuracy in cardiovascular events.
Decoding your lipid profile
A standard lipid profile generally includes total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides and non-HDL cholesterol. Let’s take a moment to explore each measurement in a little more detail.
- Total cholesterol: This encompasses all the other components, including LDL, HDL and triglycerides. However, the total number does not simply equal the summation of these individual components.
- LDL cholesterol: This is low-density lipoprotein cholesterol, also known as bad cholesterol. It is the lipid particle that builds up in the plaque deposits in blood vessels. It is the lipid parameter that most strongly correlates with the development of atherosclerotic disease. The higher the LDL cholesterol, the higher the risk. Conversely, the lower we can get our LDL cholesterol, the lower our risk for developing vascular disease. Generally, when it comes to LDL, lower is better in lowering our risk for vascular disease, but the specific target numbers vary based on various factors. Additionally, when thinking about these numbers, keep in mind that there is a very low risk of heart disease in the very young or hunter/gather populations. The average LDL cholesterol is 40-50 mg/dl range, about one-third to one-half the average value in adults.
- HDL cholesterol: This is high-density lipoprotein cholesterol, also known as good cholesterol. It helps remove the LDL cholesterol from our bloodstream. However, the cholesterol component of HDL is the same as the cholesterol component of LDL. It is the protein that makes HDL different. The HDL proteins grab onto the cholesterol from the cells in artery walls and take it back to the liver for elimination. More recently, studies show that HDL also has other benefits that help protect us from the effects of atherosclerosis, including antioxidant, anti-inflammatory and anti-clotting effects. For many years, we've known that there is a correlation between our HDL cholesterol level and our risk for developing vascular disease. However, unlike LDL cholesterol, this is an inverse correlation. That is, the higher our HDL cholesterol, the lower our risk, and vice-versa. A good goal to target is 40-45 mg/dl in men and 50-55 mg/dl in women.
- Triglycerides: Triglycerides are a form of fat, which the body uses to store, and transport energy. Like cholesterol, our body makes triglycerides in the liver and absorbs them from what we eat. Through both processes, extra calories are stored in the form of fatty acids in triglycerides within our fat cells for later use. During times of need, like fasting, these triglycerides are released from the fat cells into the bloodstream to provide energy to meet the body’s metabolic needs. Although it has been known for many years that very high levels of triglycerides can result in inflammation of the pancreas (pancreatitis), the role that triglycerides play in the development of vascular disease has been less clear. More recently, there has been increasing evidence from both basic science and clinical standpoints that an elevated triglyceride level is also associated with an elevated cardiovascular risk. A reduction in triglycerides, at least in some circumstances, can lower that risk.
- Non-HDL cholesterol: As the name implies, non-HDL cholesterol is simply the value for total cholesterol minus the HDL cholesterol value. For example, if your total cholesterol is 200 and your HDL is 40, your non-HDL is 160. This result indirectly measures all the bad cholesterol subtypes in the blood, including those not specifically measured in the standard lipid profile. Because it encompasses all atherogenic lipoproteins linked with an increased risk for cardiovascular disease, non-HDL cholesterol may be a better marker of vascular risk than LDL cholesterol alone. At present, most patient management decisions are based on LDL cholesterol. However, non-HDL cholesterol is becoming more widely utilized as an additional treatment goal, especially in patients with elevated triglyceride levels. In general, the treatment goal for non-HDL cholesterol is 30 mg/dl above the individual's goal for LDL cholesterol.
More to come
Lifestyle and medication can both play a significant role in modifying your risk. In Part 2 of this blog, we’ll explore ways to improve our risk by improving our lipids.
