Having low levels of high-density lipoprotein (HDL) cholesterol puts you at risk for a slew of poor health conditions, but new research has found that there may be one more to add to the list: COVID-19.

Key Takeaways

  • New research linked low levels of good HDL cholesterol to a greater risk of testing positive for COVID-19.A growing body of evidence has linked cholesterol levels to COVID-19 risk.Researchers aren’t entirely sure why this link exists, but they propose several theories.

The April study, which was published in PLOS One, analyzed data from 9,005 British volunteers over the age of 40 in the U.K. Biobank who were tested for SARS-CoV-2, the virus that causes COVID-19, between March 16 and July 14, 2020. The researchers specifically looked at participants’ blood work, alcohol intake, and whether they had diabetes. 

Here’s what they discovered: Study participants who tested positive for COVID-19 were more likely to have type 2 diabetes. Those who tested negative were more likely to have high levels of HDL cholesterol.

HDL cholesterol helps clear fats from your bloodstream. That’s why it is known as the “good” cholesterol, in comparison to low-density lipoprotein cholesterol (LDL), which is known as the “bad” kind. 

But when the researchers controlled for HDL levels, they found that the increased risk of testing positive due to body mass index (BMI) and type 2 diabetes was no longer statistically significant, implying that cholesterol levels played a major role.

Why Cholesterol Levels May Impact COVID-19 Risk

The study didn’t investigate why this might be the case, but study co-author Charles C. Hong, MD, PhD, director of cardiovascular research at the University of Maryland School of Medicine, tells Verywell there are some theories.

“The link between obesity and type 2 diabetes with COVID-19 was one of the earliest and striking findings of this pandemic,” he says. “Because obesity and type 2 diabetes are known to alter inflammatory processes in the body, they are commonly thought to increase susceptibility to COVID-19 complications.” 

But, Hong points out, obesity and type 2 diabetes can also impact a person’s HDL cholesterol levels. “Our findings suggest that much of this association of obesity and type 2 diabetes with COVID-19 may be due to lower HDL cholesterol levels we see in individuals with these conditions,” he says.

Hong says it’s “unknown” why their research found that people with high levels of good cholesterol and lower body weight were more likely to test negative for the virus. “Earlier studies showed that when someone gets COVID-19, the lower HDL at the time of diagnosis and the steeper drop in HDL is associated with more severe disease and worse outcomes,” he says.

Previous research has also located a link between cholesterol and the course of COVID-19 disease. A study of 1,411 people published in the journal Scientific Reports in March found that those who were hospitalized with severe COVID-19 had low HDL levels and higher levels of triglycerides, a type of fat found in the blood.

Hong’s study found that low baseline HDL levels measured years before the pandemic is linked to a higher rate of testing positive for COVID-19.

“Together, these results suggest that HDL may confer some protection against this virus, and the low HDL level is bad,” he says. “This is also in agreement with even earlier studies suggesting that low HDL is associated with higher rates of infections and sepsis in general.”

It’s hard to say whether it’s the actual HDL that plays a role or other factors, Robert Greenfield, MD, cardiologist and medical director of non-invasive cardiology and cardiac rehabilitation at MemorialCare Heart and Vascular Institute at Orange Coast Medical Center in California, tells Verywell. “Maybe it has to do with other abilities that HDL has in its ability to work with the immune system, but maybe not,” he says. “If someone has diabetes—which is a risk factor for severe COVID—they would also likely have low HDL.”

Hong agrees that there are questions about what role, exactly, HDL plays in everything. “What we don’t know is whether HDL confers direct protection against the virus, or is a surrogate for some unknown protective factors,” he says.

How to Improve Cholesterol Levels

It’s not entirely clear why low HDL cholesterol levels seem to be linked with more severe COVID-19 outcomes, but Hong says it’s a good idea to do what you can to raise your HDL levels while also lowering your LDL cholesterol levels.

What This Means For You

Doing your best to lower your levels of LDL cholesterol and raise your levels of HDL cholesterol can improve your overall health—and maybe even your COVID-19 risk. Talk to a doctor about your cholesterol levels and how to keep them in a healthy state. Some lifestyle changes that can help include limiting your saturated fats and exercising.

“Diet and exercise can reduce weight, reduce the risk of developing type 2 diabetes and improve cholesterol levels,” he says. “Diet and exercise are win-win since they are also good for your heart health.”

He also recommends the Mediterranean diet, which is known to improve HDL cholesterol. 

The American Heart Association (AHA) suggests limiting the amount of saturated fat you eat to less than 6% of daily calories, and minimizing the amount of trans fat you eat. That means choosing skim milk, low-fat or fat-free dairy products over red meat and dairy products made with whole milk. It’s also a good idea to limit fried food and cook with healthy oils, like vegetable oil, the AHA says.

If you know your cholesterol levels aren’t ideal or you’re concerned about your cholesterol, talk to a doctor. If lifestyle modifications don’t help, Hong says that medication can help lower your LDL cholesterol and raise your HDL cholesterol. The end goal is to improve your health and maybe even decrease your COVID-19 risk.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.