BETHESDA, Md. — There may be no such thing as “good” cholesterol after all, according to researchers with the National Institutes of Health.
Their study found that the “healthy” blood fats do not protect against cardiovascular disease and can even increase the risk. Known medically as high-density lipoprotein (HDL) cholesterol, the team adds these levels may not be an effective screening tool for patients at risk of heart disease.
Low levels displayed a link to heart attacks in Caucasians but did not increase the risk among their Black peers. Meanwhile, high amounts did not benefit either group. The findings are based on a review of almost 24,000 adults across the U.S.
“The goal was to understand this long-established link that labels HDL as the beneficial cholesterol, and if that’s true for all ethnicities,” says senior author Nathalie Pamir, Ph.D., an associate professor of medicine within the Knight Cardiovascular Institute at Oregon Health & Science University, in a media release. “It’s been well accepted that low HDL cholesterol levels are detrimental, regardless of race. Our research tested those assumptions.”
The study adds to evidence that cholesterol can become abnormal and lead to blocked blood vessels. A bloodstream tussle takes place between “bad” or LDL (low density lipoprotein) cholesterol — which dumps fat in the arteries — and “good” cholesterol that sweeps it away.
However, evidence is growing that more of the latter is not always better. The latest results may help find new ways to protect the heart. Eating olive oil, fish, and nuts raises levels of HDL cholesterol. It is one of the things doctors test for when predicting your risk for a future heart attack. Repeated trials that raise HDL with drugs have flopped, however, leading doctors to think something else is going on.
‘Bad’ cholesterol still increases heart disease risk slightly
The U.S. team reviewed data from 23,901 participants in the REGARDS (Reasons for Geographic and Racial Differences in Stroke) study. Previous research that shaped perceptions about “good” cholesterol levels and heart health in the 1970s included mostly white adults.
So, Prof. Pamir and colleagues looked at how cholesterol levels from heart disease-free middle-aged adults overlapped with future cardiovascular events. They enrolled between 2003 to 2007, with researchers analyzing information collected over more than a decade.
Those with increased “bad” cholesterol and harmful blood fats called triglycerides had modestly increased risks for cardiovascular disease. However, this study is the first to find lower HDL cholesterol levels only predicted increased cardiovascular disease risk among white adults.
It also provides new insight into other studies which have found high “good” cholesterol levels are not always associated with reduced cardiovascular events. The analysis was the largest to indicate this was true for both Black and white individuals, suggesting higher than optimal amounts may not provide benefits.
“What I hope this type of research establishes is the need to revisit the risk-predicting algorithm for cardiovascular disease,” Pamir says. “It could mean that in the future we don’t get a pat on the back by our doctors for having higher HDL cholesterol levels.”
Could ‘high-quality’ cholesterol be the answer?
As researchers study HDL cholesterol’s role in supporting heart health, they are exploring different theories. One is quality over quantity. That is, instead of having more HDL cholesterol, the quality of its function in picking up and transporting excess cholesterol may be more important.
They are also taking a microscopic look at its properties, including analyzing hundreds of proteins linked with transporting cholesterol. Varying associations, based on one or more, may improve cardiovascular health predictions.
“HDL cholesterol has long been an enigmatic risk factor for cardiovascular disease,” explains Sean Coady, a deputy branch chief of epidemiology within the National Heart, Lung, and Blood Institute (NHLBI)’s Division of Cardiovascular Sciences. “The findings suggest that a deeper dive into the epidemiology of lipid metabolism is warranted, especially in terms of how race may modify or mediate these relationships.”
Cardiovascular disease is the world’s biggest killer, claiming around 18 million lives a year. Risk calculators using HDL cholesterol could lead to inaccurate predictions for black adults.
“When it comes to risk factors for heart disease, they cannot be limited to one race or ethnicity,” Pamir concludes. “They need to apply to everyone.”
Participants shared similar characteristics such as age, cholesterol levels, and underlying risk factors for heart disease like diabetes, high blood pressure, or a history of smoking. During the study period, 1,615 experienced a heart attack, some of whom died.
The findings appear in the Journal of the American College of Cardiology.
South West News Service writer Mark Waghorn contributed to this report.