What is Cholesterol?

You may already be aware that cholesterol as a risk factor for heart disease. But cholesterol is also vital to good health. Cholesterol is a type of a lipid, a soft, waxy substance that contributes to the structure and stability of cells, to the manufacturing of hormones and to several other biological functions.

Cholesterol is manufactured by the liver starting from very simple ingredients. You can also get cholesterol by consuming foods that are derived from animal sources such as meat, eggs and dairy products. But for most of us, the body manufactures all the cholesterol we need from other fats in your diet; most people don't need to consume any cholesterol to maintain health.

What are the risks of too much cholesterol?

Although cholesterol is vital to a range of life-sustaining functions, too much cholesterol in your blood stream becomes a major risk factor for heart disease. Excessive cholesterol can cause build-up of atherosclerotic plaques in the arteries. Accumulation of plaque in arteries can block blood flow over time.

Cholesterol plaques that form in the coronary arteries (the arteries that supply blood to the heart) can lead to a heart attack, while plaques that form in the carotid arteries (the arteries that supply blood to the brain) can lead to a stroke.

What causes excessive cholesterol in the blood?

Too much cholesterol can arise two main ways. First, too much cholesterol or fat - which the liver uses to make cholesterol - is consumed in the diet and finds its way into the blood stream. Second, your body may be programmed (genetically) to overproduce cholesterol. Or it may be a combination of these factors.

How does cholesterol travel through the body?

Your blood is largely made up of water. Cholesterol – a lipid – does not dissolve in water. So there is a problem. Cholesterol – and another lipid called triglycerides – has to travel from the intestine and liver to the rest of the body through the blood stream, but they cannot dissolve in the blood. Therefore, to circulate through your blood, the lipids combine with special proteins to form tiny particles called "lipoproteins" (= "lipid" plus "protein"). Lipoproteins are microscopic spheres that can dissolve in water; they look a little like "M&M's", with lipids inside and protein coating on the outside. They shuttle cholesterol through the bloodstream.

There are four types of lipoproteins, each differing in size and in the ratio of cholesterol and triglycerides to protein. The main lipoprotein types that carry cholesterol are called "low-density lipoprotein" (LDL) and "high-density lipoprotein" (HDL).

What is the difference between good and bad cholesterol?

LDL cholesterol, the so-called "bad" cholesterol, is transported to cells throughout the body where it's used to repair cell membranes or make hormones. But LDL cholesterol can also accumulate in the walls of your arteries, just as hard water promotes a build-up of lime inside the plumbing of your house. Cholesterol deposits, called plaques, are spotty, rather than evenly coated, throughout the arteries. These plaques can sometimes grow large slowly or they can suddenly break open, causing a rapid blockage of an artery. If the plaques occur in critical arteries, such as the coronary arteries, a heart attack can occur.

HDL, the so-called "good" cholesterol, is transported to the liver, where it's taken up and removed from the body. HDL can be thought of as the "clean-up crew" that mops up excess cholesterol from the tissues and disposes of it before it can do any damage. HDL particles can remove cholesterol from the arterial plaques, and these keep the plaques from growing too large.

In fact, there is no real "good cholesterol": cholesterol is cholesterol. It is the lipoprotein HDL that is "good", not the cholesterol that it carries. But laboratories measure HDL cholesterol rather than HDL itself.

What type of tests are done to measure cholesterol?

No single blood test of cholesterol or ratio of cholesterol numbers provides an absolute standard for measuring heart disease risk. Your "lipid profile" includes the following measurements: total cholesterol, LDL cholesterol, HDL cholesterol and triglycerides.

Total cholesterol, LDL cholesterol, and HDL cholesterol readings reflect a dynamic process going on inside your blood vessels. Cholesterol is deposited in the walls of blood vessels and then taken away. The total cholesterol level is the crudest look at this process. The LDL and HDL numbers give a more detailed look at the two-way traffic inside your blood vessels.

What should my target levels be for total, LDL, and HDL cholesterol?

The target levels for the blood lipid profile are not the same for all people. Careful research involving hundreds of thousands of patients over the last 30 years has shown that people who have a high-risk of a heart attack or stroke need to work hard to balance their lipid profile – to lower total and LDL cholesterol and to raise HDL cholesterol.

The most effective and proven way to balance the lipid profile is by lowering the levels of LDL-cholesterol. It is also important to lower the ratio of total to HDL-cholesterol. In Canada, these are the two numbers that physicians use to judge the effectiveness of treatments.

The lipid profile levels that Canadian physicians target to prevent future heart attacks and strokes depend on the patient's risk of their condition. The higher the risk, the stricter the targets:

• You are considered to be at high risk if you have already had a heart attack, stroke, angina, angioplasty, stent or bypass, or if you diabetic or if you have at least three risk factors such as smoking, hypertension, male sex or older age.
  
  
• You are considered to be at medium risk if you are free of any disease history, but have approximately two risk factors.
  
  
• You are considered to be at low risk if you are free of any disease history, but have zero or perhaps only one risk factor. You health care professional can more accurately determine your level of risk.

The above are only recommended guidelines; physicians may still use their judgement and experience to determine whether your personal levels on treatment are satisfactory from your entire situation.

But, based on the type of evidence that is the strongest for physician-randomized, double-blinded, placebo controlled clinical trials. The overwhelming evidence is that if the LDL and total cholesterol to HDL ratio can be lowered – of course safely and with no risk or minimal side-effects – patients, especially those considered to be "high risk", live longer and live better. An ounce of prevention is truly worth a pound of cure in these instances.

Am I at risk at developing heart disease or stroke?

A person's level of risk depends on many risk factors that are taken into account by your doctor or health care professional. One of the strongest predictors of a future heart attack or stroke is that you have already had one, or that you have required a procedure such as balloon angioplasty, coronary artery stent placement or bypass surgery.

Without adopting preventative measures - including bringing the lipid profile into a better balance – the risk of a second heart attack or stroke or of premature failure of your angioplasty, stent or bypass grafts is very high if you have already had a heart attack, stroke, angina, angioplasty, stent or bypass.

We know that aggressive treatment of the lipid profile, by lowering LDL cholesterol and improving the total cholesterol to HDL ratio, will add years to your life and keep you out of the emergency room and coronary care unit. Treatment also keeps stents and bypass grafts open longer, reducing the need for repeat procedures in the future.

Research has shown that lipid management – typically with diet and medications that balance the lipid profile mainly by lowering LDL-cholesterol – can extend life by years and can cut the risk of having a future heart attack or stroke by half or more.

The best evidence exists for medication called "statins". These drugs have truly revolutionized medical practice and have been responsible for adding literally millions of disease-free years of life to patients around the world.

What kind of treatments are there for cholesterol disorders?

• Diet and weight loss. A change in your diet can lower LDL cholesterol by 10-15%. Total cholesterol and triglycerides can also be lowered and HDL cholesterol can sometimes increase. Weight loss can have similar effects, and can also lower blood glucose and reduce the risk of developing diabetes. Details for an appropriate cholesterol diet can be provided by a dietician. See Patient Resources
  
  
• Activity. An increase in activity can help lower total and LDL cholesterol and raise HDL cholesterol. It can also lower blood glucose and reduce the risk of developing diabetes.
  
  
• Statins. The most commonly used medications in Canada to improve the lipid profile are called statin drugs and include lovastatin (Mevacor), simvastatin (Zocor), pravastatin (Pravachol), fluvastatin (Lescol), atorvastatin (Lipitor) and rosuvastatin (Crestor). These drugs primarily lower LDL cholesterol but can have other beneficial effects. The lives of hundreds of thousands of people have been extended for a total of millions of years because of statin drugs. They are very safe and effective. In about 5% of people, statins can produce certain side effects, such as muscle aches and increases in blood levels of AST and CK (see above). The side effects are completely reversible upon stopping the medication.
  
  
• Cholesterol absorption inhibitors. Ezetimibe (Ezetrol) is a drug that works by reducing cholesterol absorbed from the gastro-intestinal tract. It is very safe and well tolerated and works well in patients who are intolerant to statins. It also works well in combination with statins.
  
  
• Fibrates. These drugs, including gemfibrozil (Lopid), fenofibrate (Lipidil) and bezafibrate (Bezalip) are useful for lowering elevated levels of triglycerides. Side effects are uncommon.
  
  
• Niacin. Niacin (nicotinic acid) and its extended-release version (Niaspan) are forms of vitamin B3 that have been shown to improve the entire lipid profile. Many people can develop skin rash, itching, flushing or headaches shortly after taking niacin; these side effects can get better with time and are reduced with the Niaspan formulation.
  
  
• Bile acid binding resins. These older medications include cholestyramine (Questran) and colesevalam (Cholestagel), and work in the gastrointestinal tract. They are not absorbed into the blood and so do not have many of the same side effects as statins. However, they are relatively less effective in lowering LDL cholesterol and they do produce gastro-intestinal side effects.
  
  
• Over-the-counter natural or homeopathic cholesterol "cures". The majority of over-the-counter cholesterol and lipid so-called "cures" have never been proven their worth in reducing the risk of a heart attack or stroke. In contrast, the prescription medications listed above all have such proof. While some patients might get some improvement in lipid profile with over-the-counter agents, the results are highly variable and cannot be used to substitute for prescription medication, especially for patients in the high-risk category.
  
  
• See our suggestions in Patient Resources

What is Metabolic Syndrome?

The clustering of cardiovascular risk factors is recognized as being a major health issue. The metabolic syndrome is defined in qualitative terms and encompasses abdominal obesity, insulin resistance, elevated plasma triglyceride and low HDL-C levels and high blood pressure.

back to top