'Good' Cholesterol May Not Protect Against Heart Disease, Study Finds

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For decades doctors have been telling their patients that high levels of HDL, otherwise known as “good cholesterol,” could protect them from heart disease. But a new study suggests that having a lot of so-called good cholesterol doesn’t mean a lower risk of heart attacks.  

That doesn’t mean HDL levels have no impact.

An analysis of data from nearly 24,000 American adults revealed that too little HDL cholesterol was associated with an increased risk of heart disease — in white adults, but not in Black adults, researchers reported Monday in the Journal of the American College of Cardiology.  

The new findings surprised the researchers, who originally designed their study to understand how cholesterol levels in Black and white middle-aged adults without heart disease affected their future risks. Previous research on "good" cholesterol and heart disease consisted of mostly white adults. 

“I did not expect high levels of HDL would not be protective,” said the study’s senior author, Nathalie Pamir, an associate professor of cardiovascular medicine in the Oregon Health and Science University School of Medicine. “And I certainly did not expect low levels to have no predictive value for Black adults.”

The new research, co-funded by the National Institutes of Health, is part of a growing body of evidence disputing that high HDL cholesterol levels are protective against heart disease, experts say, although people may not always be getting the message.

“Those of us with high HDL have been getting a pat on the back from our doctors,” said Pamir, who is also a researcher at the Center for Preventive Cardiology at OHSU’s Knight Cardiovascular Institute. “We’ve been told your HDL is good so don’t worry. You’re protected.”

Low density lipoprotein, or LDL, contributes to fatty buildups in the arteries, raising the risk of heart attack and stroke. It had long been thought that high density lipoprotein, or HDL, is protective because it carries cholesterol to the liver, where it is disposed of.

What’s clearer now is that high HDL just adds to the total cholesterol number.

“It’s still cholesterol at the end of the day,” Pamir said. “More and more studies are coming out showing that HDL levels above 80 are detrimental with regards to cardiovascular outcomes.”

The findings suggest that the algorithms used to calculate an individual’s coronary heart disease risk need to be adjusted since they currently show a lower risk if HDL is high, Pamir said.

Risk calculations also need to take race into account, she said, adding that the differences seen in Black adults may be because of socioeconomic factors rather than genetics.

What Is A Healthy Cholesterol Level? 

Right now, a major focus should be on the total cholesterol number, Pamir said.

Cholesterol levels are measured in milligrams per deciliter of blood (mg/dL). According to the American Heart Association, the optimal total cholesterol level for an adult is about 150 mg/dL, with LDL levels at or below 100 mg/dL.

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