Fat in the blood is generally present in predominantly two forms – cholesterol and triglycerides. When a cholesterol profile is performed, blood is taken, analysed and the levels of different types of fats are measured. Cholesterol usually travels in the blood stream in combination with special proteins called lipoproteins of which the two predominant groups are low density lipoprotein (LDL), the so called “bad cholesterol” and high density lipoprotein (HDL), sometimes simplistically referred to as “good cholesterol”.

The complex of cholesterol and lipoprotein are referred to as LDL cholesterol (LDL-C) and HDL cholesterol (HDL-C), respectively. For routine clinical use, the total cholesterol, LDC, HDC, and triglycerides are reported. These values can be used to assess the risk of atherosclerotic vascular disease and in combination with other findings: presence of hypertension, diabetes, smoking, family history, etc, can be used to decide on the need for treatment of blood cholesterol and how aggressive this treatment should be.

HOW ARE LDL CHOLESTEROL AND HDL CHOLESTEROL DIFFERENT?

LDL cholesterol and HDL cholesterol can be thought of as having different functions. LDL cholesterol transports cholesterol from the liver to tissues in the body, whereas HDL cholesterol is responsible for returning cholesterol from peripheral tissues to the liver where it can be absorbed and broken down. The higher the level of LDL cholesterol in the blood stream is the higher the risk of laying down cholesterol in the arteries of the body leading to atherosclerosis.

Atherosclerosis is a process that can occur in all arteries of the body but has a predilection for the arteries of the brain, heart, kidneys, and lower extremities. Over time, this buildup of cholesterol can impair blood flow leading to clinical syndromes of heart attack, stroke, leg pain and amputations. High levels of HDL cholesterol given its role in returning cholesterol to the liver tend to be protective against the development of atherosclerosis and that is why it is often referred to as the “good cholesterol”.

WHAT ARE THE USES OF CHOLESTEROL AND TRIGLYCERIDES?

Cholesterol is used in a variety of different metabolic pathways in the body. It is used in the production of hormones such as estrogen and testosterone, vitamins such as vitamin D and in the production of structures such as cell membranes. Triglycerides are used to store excess energy. When the body has calories more than its immediate needs, these calories are converted into triglycerides and stored in fat and muscle cells. These triglycerides can be broken down and mobilised when the body has need for energy, for example, during exercise.

WHERE DOES THE CHOLESTEROL IN HE BLOOD COME FROM?

It is a common misconception that cholesterol from the diet is responsible for most of the cholesterol in the blood stream. On average 80 per cent of the cholesterol that is in the blood is produced by the liver and sent into the blood as LDL cholesterol, leaving 20 per cent which is contributed by the diet. The components of diet, that is intake of fats (saturated, non-saturated and trans-fats), carbohydrates and the amount of caloric intake do play a role in determining the levels of cholesterol and triglycerides. They can also impact the process of cholesterol production in the liver and the amount of triglycerides in circulation. Importantly, dietary control of saturated fats, carbohydrates and trans-fats are components of a heart healthy diet. However, in patients who need significant reduction of LDL cholesterol (30-50 per cent), dietary measures alone tend to be insufficient and there is often the need for drug therapy.

WHY DO WE TREAT PATIENTS FOR CHOLESTEROL ABNORMALITIES ANDWHAT LEVELS OF CHOLESTEROL ARE CONSIDERED NORMAL?

The answer to the second part of this question is not as clear cut as it may seem. As cardiologists and preventive physicians, we care about cholesterol only so much as it is a marker for the risk of atherosclerotic disease. The real benefit of treating cholesterol abnormalities is the fact that we can reduce death and disability from atherosclerosis.

From many decades of research, it is quite clear that high levels of total and LDL cholesterol are associated with increased risk of atherosclerosis and its clinical sequalae like heart attacks and strokes. High levels of HDL are associated with lower risk. There does not appear to be a definite bottom floor for LDL cholesterol number, below which there is no risk. Given these findings, most preventative bodies look first at the risk of atherosclerotic complications like heart attack, stroke and cardiovascular death in each person and given this level of risk we then decide on whether the patient needs treatment and how aggressive this treatment should be. Most of the focus is on LDL cholesterol (bad cholesterol) because almost all the data that suggests that drug therapy for cholesterol abnormalities lowers risk of cardiac and vascular disease results from treating LDL cholesterol with medications known as statins.

The focus on level of risk as opposed to the “cholesterol numbers” can be seen in the latest American College of Cardiology (ACC) American Heart Association 2018 guidelines as well as the 2019 European Society of Cardiology guidelines. For patients who are low risk (patients whose 10-year risk of cardiovascular disease is less than five per cent) there is little benefit of prescribing medical therapy for elevated LDL cholesterol.

In this group of patients, 4.9mg/dl is the value above which there is universal agreement that drug therapy is required. Below this level, different physicians will initiate drug therapy at different levels of LDL cholesterol usually after assessing individual risk and with patient discussion. In contrast, patients at the highest levels of risk (10-year risk of cardiovascular disease 20 per cent or higher or with diagnosed vascular disease) are given drug therapy almost irrespective of the baseline level of the LDL cholesterol with the aim to lower LDL cholesterol by greater than 50 per cent. The target LDL for these patients can be as low as 1.4-1.7mg/dl. Clearly many patients fall within these extremes and the best idea of what an individual’s “normal” or target cholesterol should be is best decided after discussion with their personal physician/cardiologist. 

DO I NEED DRUG TREATMENT FOR LOW HDL CHOLESTOROL OR HIGH TRIGLYCERIDES?

As noted above, the evidence that we can improve patient outcome in terms of cardiovascular disease with medications to increase HDL cholesterol or reduce triglycerides is quite limited and for the most part we do not target drug treatment for these abnormalities. We rather depend on lifestyle measures of regular exercise, achievement, and maintenance of an ideal body weight, reducing alcohol intake and lowering intake of high glycemic index carbohydrates. It should be noted that extreme elevation of triglycerides is a risk factor for another medical condition called pancreatitis so that drug therapy can be given for that indication.

Can drug treatment make my cholesterol too low?

The data obtained from clinical trials suggest that there are no adverse effects to lowering cholesterol levels to 1.4mg/dl on average.

WHEN AND HOW SHOULD I HAVE MY CHOLESTOROL CHECKED?

For adults, it is recommended that a cholesterol profile be check in their early 20s and if found to be normal should ideally be repeated every five years. Traditionally this is done as a “fasting” sample, for example, after an overnight fast. There are some data which suggests that the fasting period may be unnecessary for some patients. In the future this may allow for greater convenience in cholesterol testing.

We hope that the above has helped to clarify some common issues around cholesterol and triglycerides, particularly as it pertains to the risk of cardiovascular disease. We all should remember that cholesterol management is only part of a heart healthy lifestyle. While the focus of today’s article was on testing and treatment, it is important to remember that lifestyle measures including a heart healthy diet, regular aerobic exercise and achievement and maintenance of an ideal body weight all play a role in improving or cholesterol profile and overall cardiovascular health.

Dr Ernest Madu, MD, FACC; and Dr Paul Edwards, MD, FACC are Consultant Cardiologists at Heart Institute of the Caribbean (HIC) and HIC Heart Hospital

Dr Madu is a main TED Speaker whose TED talk has been translated into 19 languages, seen, and shared by more than 500,000 viewers. He has received the Distinguished Cardiologist Award, the highest award from the American College of Cardiology and has been named among the 100 most influential people in health care and among the 30 most influential in public health. Dr Madu is also a recipient of the Global Health Champion Award from the University of Pennsylvania. Dr. Madu was past CEO of HIC and is currently the Chairman of IHS Holdings Ltd, an asset management company with interests in the USA, Africa, and the Caribbean.

Correspondence to info@caribbeanheart.com or call 876-906-2107