Too much of a good thing is not always good for you, and that’s what researchers at the University of Copenhagen believe when it comes to “good” cholesterol in the body – also known as HDL (high-density lipoprotein).
While it’s believed that high levels of HDL in the blood are good, the new study from the University of Copenhagen refutes the commonly held claims by such bodies like the Heart & Stroke Foundation and the American Heart Association.
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The research team says they’ve shown that people with “extremely high levels” of HDL have a higher mortality rate than those who have normal levels.
For men in particular, the reported mortality rate by the study says it was 106 per cent higher than for the normal group. For women, the mortality rate among those with high levels was 68 per cent higher.
“These results radically change the way we understand ‘good’ cholesterol,” Borge Nordestgaard, co-author of the study, said in a statement. “Doctors like myself have been used to congratulating patients who had a very high level of HDL in their blood. But we should no longer do so, as this study shows a dramatically higher mortality rate.”
The study looked at data for 116,000 people from the Copenhagen City Heart Study and the Copenhagen General Population Study. They compared that data with mortality data form the Danish Civil Registration System. They also followed the subjects for an average of six years, and based the study on over 10,500 deaths.
According to the study, 0.4 per cent of the men and 0.3 per cent of the women in the study had an extremely high level of HDL in their blood. Another 1.9 per cent of men had a very high level.
Besides linking high HDL levels to high mortality, the study also found a high mortality rate for people with extremely low levels of HDL. Those with “medium levels” of HDL had the lowest mortality. This level was 1.9 mmol/L for men, and 2.4 mmol/L for women.
However, as the study is observational, registered dietitian Andrea D’Ambrosio says it’s best to take the results with a grain of salt.
“There are a few things we have to consider with this study and we have to be careful not to blow it out of context,” D’Ambrosio, spokesperson for Dietitians of Canada and dietitian at Dietetic Directions, says. “The study is showing that these things (high HDL levels and mortality) are related but it doesn’t mean that HDL is causing you to die. It might just be that someone with a health condition has a high HDL level, and it’s the health condition is why they’re dying.”
When looking over the research, D’Ambrosio – who was not a part of the study – noticed researchers hadn’t taken several other factors into account when comparing data, such as underlying health conditions.
And it’s overlooked factors such as these that skew the results and interpretation of the results.
“Excessively high HDL cholesterol levels can be linked to things like having a thyroid disorder or an inflammatory disease or excessive alcohol consumption,” D’Ambrosio points out. “And certain types of medications will actually increase HDL cholesterol. Even something like Omega-3 fats and supplements lower triglycerides in the blood, but they also increase HDL cholesterol.”
HDL, D’Ambrosio explains, is referred to as the “good” cholesterol because it helps to remove other harmful forms of cholesterol from your blood.
“We can think of HDL cholesterol as kind of like a dump truck,” she says. “It basically picks up the bad cholesterol, brings it to the liver to be metabolized so that we can lower our LDL (low-density lipoprotein) – or our lousy cholesterol that causes that plaque buildup in our arteries, and is linked to heart disease, heart attacks and strokes.”
HDL cholesterol is naturally made by our bodies but can be increased through diet.
Examples of these foods include olive oil, beans and legumes, high fibre fruit, nuts and more, Healthline reports,
According to the Heart & Stroke Foundation, dietary cholesterol – found in eggs, poultry, meat and regular dairy products – has less of an impact on blood cholesterol than foods with saturated and trans fats.
Foods that have saturated fat include processed foods, fatty meats, full-fat milk products, butter and lard. Foods with trans fat include partially hydrogenated margarines, deep-fried foods and many packaged crackers, cookies and commercially baked products.