After all, there may be no such thing as ‘good’ cholesterol, a federally funded study suggests.
The researchers found that high levels of high-density lipoproteins (HDL) were not associated with a lower risk of developing heart disease.
HDL absorbs cholesterol in the arteries and transports it back to the liver, which then removes it from the body. For this reason it has been called ‘good’ cholesterol.
LDL cholesterol, on the other hand, is responsible for damaging blood vessel walls and contributes to the buildup of inflamed fatty deposits known as plaques, which increases your risk of heart attack or stroke.
The study, on 24,000 Americans, was funded by the National Institutes of Health (NIH), the government agency dedicated to medical and scientific research.
It was published in the Journal of the American College of Cardiology.
The study’s lead author, Dr. Nathalie Pamir, an associate professor of medicine at Oregon Health & Science University, said: “The goal was to understand this long-established link that labels HDL as the beneficial cholesterol, and if that’s true for all ethnicities.”
‘What I hope this type of research establishes is the need to revise the risk prediction algorithm for cardiovascular disease.
“It could mean that in the future our doctors won’t pat us on the back for having higher HDL cholesterol levels.”
Cholesterol is a waxy, fat-like substance produced by the liver and is found in every cell in the body. It is crucial to produce hormones, vitamin D and the key components to aid in digestion.
The Oregon researchers found that while LDL cholesterol is linked to an increased risk of developing heart disease, higher levels of “good” cholesterol were not associated with reduced risk of cardiovascular disease in black or white adults. Their findings upset the general medical consensus on the role of cholesterol in heart health.
‘Good’ and ‘bad’ cholesterol
The ‘good’ HDL cholesterol breaks down plaque cholesterol and carries it back to the liver, where it is processed and removed from the body.
‘Bad’ LDL cholesterol is responsible for damaging blood vessel walls and contributes to the buildup of inflamed fatty deposits known as plaques, which increases the risk of heart attack or stroke.
Cholesterol comes from two sources: our liver makes it, and we also get it from the food we eat. It is carried in the blood in particles known as lipoproteins.
A total cholesterol level of five or higher is considered a risk, although current guidelines do not give a maximum HDL level.
Recent evidence suggests that HDL loses its protective quality once it exceeds 1.4 mmol/L.
The Oregon team analyzed data from a decade of nearly 24,000 American adults who participated in the federal Reasons for Geographic and Racial Differences in Stroke survey between 2003 and 2007.
The study found that while low HDL cholesterol levels predicted increased risk of heart attacks or cardiac deaths for white adults, the same was not true for black adults.
Furthermore, higher HDL cholesterol levels were not associated with a reduced risk of cardiovascular disease in either group.
High HDL cholesterol levels have been reported to speed up the process of atherosclerosis, a condition in which plaque made of fat, cholesterol, calcium, and other substances builds up on the inner walls of arteries.
Plaque can cause arteries to narrow, blocking blood flow. The plaque can also burst, leading to a blood clot.
Adults with elevated levels of LDL, or ‘bad’ cholesterol, had a slightly increased risk of cardiovascular disease, which aligns with previous research findings.
The analysis was the largest study in the US to show that excess good cholesterol may not provide the kind of cardiovascular benefit that health professionals believed.
The Oregon team’s work is part of a growing body of evidence showing that too much ‘good’ cholesterol may actually be detrimental to your health.
In 2018, a major analysis looked specifically at the relationship between HDL and the risk of heart attack and death.
For four years, researchers at the Emory University School of Medicine in Atlanta followed nearly 6,000 patients, most with heart disease and with an average age of 63. During the study, 13 percent suffered a heart attack or died from cardiovascular disease. But something quite unexpected was seen.
There were more heart attacks in those with very low HDL, less than 1, which was not surprising. But a similarly high number was seen in those with very high HDL levels of more than 1.4. Only those with HDL levels between this range saw a lower risk of heart attack.
A massive 2016 study published in the Journal of the American College of Cardiology consisted of almost 632,000 Canadian adults.
The researchers found that people with the lowest levels of “bad” cholesterol had higher rates of death from heart disease and stroke over five years, but that risk did not decline steadily as “good” cholesterol levels rose. “. Instead, it dipped before reaching a plateau.
In an earlier study, researchers at the Harvard School of Public Health determined that a small protein found in HDL cholesterol could increase the risk of heart disease.
Dr Pamir said: “The goal was to understand this long-established link that labels HDL as the beneficial cholesterol, and whether that is true across ethnicities.”
‘It has been well accepted that low HDL cholesterol levels are harmful, regardless of race. Our research tested those assumptions.’