Why 'Good' Cholesterol Isn't So Great After All

By Cassidy Morrison

'Good' cholesteral helps remove other forms of cholesterol from the blood. It helps keep risks of heart attack and cardiovascular disease in check. Too-high HDL levels were not associated with reduced cardiovascular disease.

There may be no such thing as 'good' cholesterol after all, a federally-funded study suggests.

Researchers found that high levels of high-density lipoprotein (HDL) were not associated with a lower risk of developing heart disease.

HDL absorbs cholesterol in the arteries and ferries it back to the liver, which then flushes it from the body. For this reason it had been dubbed 'good' cholesterol.

LDL cholesterol, on the other hand, is responsible for damaging blood vessel walls and contributes to the build-up of inflamed fatty deposits known as plaques, which raises the risk of a heart attack or stroke.

The study, on 24,000 Americans, was funded by the National Institutes of Health (NIH), the government body dedicated to medical and scientific research.

Senior author of the study 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 revisit the risk-predicting algorithm for cardiovascular disease.

'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.’

Cholesterol is a waxy fat-like substance made by the liver and is found in every single cell in the body. It is crucial to making hormones, vitamin D, and the key components to aid in digestion.

The Oregon team analyzed a decade’s-worth of data from nearly 24,000 US 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 levels of HDL cholesterol predicted an increased risk of heart attacks or cardiac deaths for white adults, the same was not true for Black adults.

Additionally, higher HDL cholesterol levels were not associated with reduced cardiovascular disease risk for 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 inside walls of your arteries.

The plaque can cause arteries to narrow, blocking blood flow. The plaque can also burst, leading to a blood clot.

Adults with heightened levels of LDL, or ‘bad’ cholesterol, had modestly increased risks for cardiovascular disease, which aligns with findings from previous research.

The analysis was the largest US study 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 that shows too much ‘good’ cholesterol can actually be detrimental to your health.

In 2018, a major analysis specifically examined the relationship between HDL and risk of heart attack and death.

For four years, researchers from the Emory University School of Medicine, Atlanta, followed almost 6,000 patients, most with heart disease and with an average age of 63. During the study, 13 per cent had 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, of less than 1, which wasn’t a surprise. But a similarly high number were seen in those with very high HDL levels, of more than 1.4. Only those with HDL levels between this range saw a lower heart attack risk.

A massive 2016 study consisted of nearly 632,000 Canadian adults.

Researchers found that people with the lowest ‘bad’ cholesterol levels had higher death rates from heart disease and stroke over five years, but that risk did not drop steadily as ‘good’ cholesterol levels rose. Instead, it dipped before hitting a plateau.

In an earlier study, researchers at the Harvard School of Public Health determined that a small protein that resides on HDL cholesterol may actually 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 if that’s true for all ethnicities.’

‘It’s been well accepted that low HDL cholesterol levels are detrimental, regardless of race. Our research tested those assumptions.’