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'Good' Cholesterol: You Can Have Too Much Of A Good Thing

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Written by Katherine Nazimek, a Communications Advisor at Sunnybrook.

"Everything in moderation." What was once my excuse to periodically indulge in some not-so-good behaviours (read: eating dessert), is now the motto too for over-indulging in those "good-for-you" things -- at least when it comes to our cholesterol.

In a recent study, researchers weigh-in on the conventional wisdom that supercharging your "good" cholesterol to very high levels can help reduce the risk of heart disease. What they found instead was that both low levels of the cholesterol -- known as high-density lipoprotein (HDL) - and very high levels could lead to a higher risk of death.

"It's been thought that raising high-density lipoprotein is the holy grail of reducing or eliminating heart disease," says Dr. Dennis Ko, cardiologist at Sunnybrook Health Sciences Centre, senior scientist at the Institute of Clinical Evaluative Sciences, and the study's lead investigator. "But instead of seeing a linear correlation between HDL and mortality, we're seeing a U-shape. It tells us that beyond a certain level, HDL cholesterol isn't necessarily all that beneficial. Beyond the average values, we don't see a lower risk of death."

The study, which was published recently in the Journal of the American College of Cardiology, looked at 631,762 individuals without pre-existing cardiovascular conditions. Individuals whose HDL cholesterol levels were very low (less than 50 mg/dL or 1.3 mmol/L in women and 40 mg/dL or 1 mmol/L in men) and very high (more than 80-90 mg/dL or 2-2.3 mmol/L) experienced a greater risk of death compared to individuals who had HDL cholesterol levels that fell within intermediate ranges.

Cholesterol isn't about a battle between good versus evil.

Low-density lipoprotein (LDL) is the "bad" cholesterol that accumulates on the walls of our blood vessels and causes blockages. Our HDL, the "good" cholesterol, acts as a scavenger, grabbing hold of the bad cholesterol and carrying it to our liver to break it down.

One would think the more cholesterol we have cleaning out the bad, the better. And scientists are not yet sure why this is not the case.

"We can't abandon the concept of cholesterol being a marker of health," explains Dr. Ko, also an associate professor at the University of Toronto. "LDL cholesterol is still bad and the more you do to lower your LDL levels, whether through medication or lifestyle changes, the better your outcomes will be."


The discovery, he says, is that the HDL cholesterol levels are not a specific indicator of heart health, but rather an indicator of general health.

"Yes, low HDL levels are associated with a higher risk of cardiovascular death," admits Dr. Ko, "but the data tells us that the HDL level is not the modifiable risk factor that if we change, we will improve the cardiovascular outcome."

The study found that individuals with lower HDL cholesterol levels were more likely to have lower incomes and unhealthy lifestyles like smoking, lack of physical activity, poor diet, and hypertension.

Howard Gaskin says these findings are a bit of a relief.

With a family history of heart disease, Howard eats well, stays active and pays close attention to his cholesterol levels: not only to keep his LDL cholesterol low, but also to keep his HDL cholesterol high.

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Howard Gaskin strives to maintain his heart health by exercising and eating well.

"It's certainly a number, a measure, a metric that I've been focused on for years," says Howard, who takes medication to lower his LDL cholesterol and admits he's been frustrated with trying to raise his HDL above what's considered average levels.

"I think I will obviously focus a lot less on HDL as a measure of the success of what I'm doing," he says.

Bottom line: It's just a number.

Dr. Ko's take-home message is simple: our HDL level is just a number that doesn't necessarily warrant the attention we've been giving it. While low levels indicate poor health, super high levels do not necessarily mean you're healthy. Instead, we need to maintain our cardiovascular health the way we're told over and over again: no smoking, exercise regularly, reduce your stress, and eat your fruits and vegetables.

"It's what you do -- your exercise, your diet -- that's more important. That's what we think is making the impact," says Dr. Ko.

So for health-conscious Howard, little has changed. "I exercise because I enjoy it, I run because I have a good time doing that. So, I'll still continue to focus on those strategies, but with different metrics in mind," he says.

Find more heart healthy tips from Sunnybrook experts at health.sunnybrook.ca

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