High cholesterol levels can lead to a build-up of plaque in the arteries, which can increase your risk of heart attack and stroke. (iStock photo)It's one of those diagnoses you'd prefer not hearing from your doctor: you have high levels of "bad" cholesterol in your blood. About 41 per cent of Canadian adults have high total cholesterol levels.

According to Statistics Canada's Canadian Health Measures Survey released on Mar. 22, 2010, 47 per cent of adults between the ages of 40 and 59 had high levels of total cholesterol, which is a measure of all cholesterol and other types of fats in the blood.

Among those aged 60 to 79, 54 per cent did. And it's not just an affliction of older adults. More than a quarter of people between the ages of 20 and 39 registered high levels of cholesterol.

The survey relied on blood samples from about 5,600 participants at 15 sites across the country, taken from March 2007 to February 2009.

High cholesterol is a condition that can be controlled — even reversed — through medication and some simple lifestyle changes. But left untreated, high cholesterol will put you at greater risk of developing heart disease — the No. 1 killer of Canadians.

What is cholesterol?

Cholesterol is a waxy substance that occurs naturally in your body. It is a type of fat known as a lipid and it is critical for the day-to-day functioning of that collection of cells that is you. Your body needs cholesterol to make cell membranes, vitamin D and hormones.

A model of a molecule of cholesterol. (iStock photo)There are two types of cholesterol:

• Low-density lipoprotein (LDL) cholesterol.
• High-density lipoprotein (HDL) cholesterol.

LDL particles are carried to body cells from the liver. HDL particles move the other way, returning extra cholesterol to the liver for disposal.

LDL cholesterol is referred to as "bad" cholesterol because when there's too much, it promotes the build-up of plaque in artery walls. As the plaque builds up, your arteries lose their elasticity and get narrower. The flow of blood is reduced, leading to atherosclerosis. If this develops in the arteries leading to and from your heart, you will develop coronary artery disease, greatly increasing your risk of heart attack.

HDL cholesterol, on the other hand, is referred to as "good" because it helps carry LDL-cholesterol away from the artery walls, lessening your chances of developing heart disease.

Where does cholesterol come from?

Most of it is manufactured in your liver: Your body produces all the cholesterol it needs. In healthy people, about 80 per cent of the cholesterol that's in the body is produced by the body. The rest comes from what you eat.

If you eat a high-fat diet — especially a diet high in saturated fats — chances are you will have elevated levels of bad cholesterol in your blood. Saturated fats raise levels of LDL cholesterol in your blood more than anything else in your diet. Trans fats are also a major culprit, as are foods that come from animal sources such as eggs, meat and some dairy products. Egg yolks and organ meat such as liver are considered very high in cholesterol.

High levels of bad cholesterol can also be hereditary.

How do I know if I have high levels of bad cholesterol?

A simple blood test can determine your cholesterol levels.

Health Canada suggests the following as guidelines for cholesterol levels:

• Total cholesterol: less than 5.2 millimoles per litre (mmol/L) Is ideal and more than 6.2 mmol/L is considered high.
• HDL cholesterol: more than 0.9 mmol/L is desirable.
• LDL cholesterol: less than 3.5 mmol/L is considered ideal and more than 4.0 mmol/L is high.

How do I minimize my risk of developing high levels of bad cholesterol?

Health Canada advises that you maintain a healthy weight, get at least 30 minutes of exercise a day and stay away from cigarettes. It also recommends reducing the total fat in your diet by:

• Choosing leaner meats, poultry and fish.
• Reducing meat portions to the size of a deck of cards.
• Eating no more than one egg yolk a week.
• Choosing skim dairy products such as skim milk, cottage cheese with 1 per cent M.F. on the label and yogurt with less than 1 per cent M.F. on the label.
• Choosing cheeses with less than 15% M.F. on the label.
• Cooking with little or no fat.
• Using vegetable oils such as olive, canola, corn, sunflower, safflower, and peanut oil in small quantities.
• Avoiding store-bought baked goods such as croissants, muffins and doughnuts.

Health Canada also recommends you eat more vegetables, fruit, whole grains such as oats or barley, and legumes such as dried peas, dried beans and lentils.

I'm healthy, fit and trim. I don't need to worry, right?

Guess again.

Anyone can have high cholesterol regardless of weight. Maintaining a healthy weight is a good foundation for a healthy lifestyle — but if high cholesterol "runs" in the family or your body isn't that efficient at disposing of bad cholesterol, you could be at risk.

Are there foods that actually lower cholesterol?

Yes. A diet high in fibre may help lower LDL cholesterol levels significantly. But it has to be soluble fibre.

Oatmeal, oat bran, kidney beans, brussel sprouts, apples, pears, psyllium, barley and prunes all contain soluble fibre. Soluble fiber appears to reduce the amount of cholesterol your body absorbs from the food you eat.

As well, walnuts and almonds also appear to help. Both are high in polyunsaturated fatty acids and help keep blood vessels healthy and elastic. Both are also high in calories, so it doesn't take much to do the trick. Too many nuts could lead to weight gain — putting you at risk, once again, for developing high cholesterol levels.

Fish — especially those high in omega-3 fatty acids — also seem to help.

If diet and lifestyle changes aren't enough, what treatments are available?

Your doctor will write you a prescription for one of a class of drugs called "statins." First approved for use more than 20 years ago, statins lower levels of LDL cholesterol. Statins are the best selling medication in the world, with an international market worth about $30 billion a year.

But 60 per cent of patients who lower their LDL levels will still get heart disease.

New research suggests that focusing on increasing levels of good cholesterol may have a great health benefit than lowering levels of bad cholesterol. Drug companies are currently testing new medications that raise HDL levels. The feeling is a combination of HDL-raising and LDL-lowering drugs could prove a potent combination in the battle against heart disease.