Confused about cholesterol?
“Doctor, is my blood cholesterol normal?” I’m asked this question repeatedly by patients. It’s understandable that they’re concerned about blood cholesterol — you’d have to be living on another planet not to have heard that blood cholesterol was the leading indicator of coronary heart disease (CHD). But is there a specific number that allows doctors to answer “Yes” or “No” to this question?
In 1988, the National Cholesterol Education Panel attempted to make the response simple. It chose a blood cholesterol level of 5.2 mmol/L as normal in Canada. This corresponds to 250 milligrams in the U.S.
Single number misleading
But zeroing in on a single arbitrary number is very misleading. For instance, it’s a fact that 35 per cent of people who develop CHD have normal blood cholesterol levels. Others with high blood cholesterol live a long life and die from non-cardiac causes. Most authorities now agree that blood cholesterol is, by itself, a poor predictor of coronary heart disease. “Know your number” is now past history.
So what is a good predictor of future heart attack? To answer this question, you he to accept that CHD is a complex disease. A lot of things don’t add up. For instance, North Americans are advised to increase their intake of veggies to decrease the risk of CHD. But how much veggies help prevent atherosclerosis? If you agree that we are distantly related to gorillas, you may well wonder — gorillas are vegetarians and yet have a high incidence of artherosclerosis!
We’re also urged to eat less fat. But most people wrongly perceive this dictum as condemning dairy products, a potentially harmful suggestion, as milk, say nutritionists, is designed by nature to support tissue growth and adds far more than calcium to the diet. In fact, studies show that those who have a poor dietary intake of calcium usually also have a poor diet. So, in the rush to fight CHD, think twice before giving up dairy products.
What should be high, what should be low
But getting back to numbers, what are considered the important ones? It’s generally agreed that the number to watch is the high HDL (high-density lipoprotein). This should be high as it helps rid the blood of excess cholesterol. The number to keep low is the LDL (low-density lipoprotein), believed to be a prime instigator of atherosclerosis. A high triglyceride level is also undesirable.
The balance of these numbers is also important. For example, having a high blood cholesterol and a high LDL can be neutralized in part by having a high HDL. And if you divide blood cholesterol by HDL and end up with a low number, all the better.
Why all this discrepancy? Because whether you drop from a coronary attack depends on many factors. Heredity is possibly the best protection against CHD. It determines how much cholesterol your liver makes every day — about 1,000 milligrams.
But just because your ancestors all lived long lives doesn’t mean you can toss caution to the wind. A lack of exercise, obesity, diabetes and smoking can still lead to CHD. Autopsies show that current North American lifestyle leaves much to be desired.
Heart attack in the young can be related to narrowed atherosclerotic coronary arteries. But in the elderly, sudden death is often due to blood suddenly forming a clot. That’s why a baby Aspirin (81 milligrams) every day is often recommended by doctors to prevent fatal clots from forming. And they may also prescribe drugs to lower blood cholesterol.
Who dies from CHD is still a little like gambling in Vegas — the numbers are only one part of the game.