Good cholesterol vs. bad cholesterol: What's the difference?

How do you lower cholesterol? What causes high cholesterol? We cover the basics, plus common misconceptions.

Mercey Livingston CNET Contributor
Mercey Livingston is a health and wellness writer and certified Integrative Nutrition Health Coach. She's written about fitness and wellness for Well+Good, Women's Health, Business Insider, and Prevention.com among others. When not writing, she enjoys reading and trying out workout classes all over New York City.
Mercey Livingston
6 min read

Modern research shows that dietary cholesterol may not be as harmful as we once thought. 

Getty Images

In the world of controversial and downright confusing topics in health -- cholesterol tops the list. Up until recently, it was considered basically the devil when it comes to heart health. But now we know that cholesterol itself is not the enemy. It's LDL cholesterol, also known as "bad" cholesterol levels in the blood that we have to worry about. 

To be clear -- cholesterol is a term used loosely, but it can mean either dietary cholesterol found in food or the cholesterol found in your body -- but the two are not the same thing. 

For many years, the general idea was that high cholesterol can lead to heart disease, so you should avoid foods high in cholesterol -- like egg yolks for example. But in 2018, the research shifted in a new direction and showed that eating dietary cholesterol does not cause heart disease, but said it's more likely trans fats or saturated fats (which are both found in foods with cholesterol) may be part of the problem. 

"Cholesterol is a waxy, whitish-yellow fat made by all animal cells. Cholesterol is a crucial building block in cell membranes and is necessary for the body to effectively produce hormones and Vitamin D," Erika Davey, physician's assistant, certified health coach and founder of Levity Health tells CNET.

For more on how cholesterol works, including the science behind dietary cholesterol and the link to heart disease, keep reading below.

Why is cholesterol important?

Despite its bad reputation, cholesterol is important for your health and it serves many purposes in the body.

Cholesterol helps your body make hormones

Cholesterol is necessary for your body to make important steroid hormones which are classified into five major groups:

  • Progestogens: Also known as progesterone, which is an important hormone for female reproductive health and pregnancy.
  • Glucocorticoids: Like cortisol, which plays a role in how the body responds to stress and it temporarily lowers inflammation when your body senses a threat. 
  • Mineralocorticoids: Aldosterone is a steroid hormone that helps the body regulate blood pressure and plays an important role in heart health.
  • Androgens: Androgens are male sex hormones; one is testosterone. 
  • Estrogens: Estrogens are onetype of female sex hormones.

Cholesterol helps make bile acids that digest and absorb fats

It may sound kinda gross, but your bile plays an important role in your health. Specifically, there are certain bile acids that you need so you can digest and absorb fats well. Cholesterol helps your body produce these acids that it needs. 

Bile acids are important for helping your body produce bile flow, which is also important for the absorption of fat-soluble vitamins. Studies also show that bile acids are important for lipid (fat), glucose (sugar) and energy homeostasis.

Cholesterol helps make vitamin D 

Cholesterol is also important for vitamin D production. Vitamin D is essential for immune health, bone health, and it plays a role in reducing inflammation. Vitamin D is one of only two vitamins that your body can produce on its own (the other is vitamin K), and you can also get it from other sources like food or supplements. 

It's also technically a hormone that regulates how much calcium is in your blood. Studies suggest that vitamin D can help prevent respiratory infections or reduce the severity of them, especially if you have a deficiency.

25 face mask styles we love that you can buy or make

See all photos

'Good' and 'bad' cholesterol, explained

You've probably heard your doctor talk about "good" and "bad" cholesterol, but what exactly does this mean? 

High-density lipoprotein is known as "good" cholesterol. HDL "is a friendly scavenger that cruises the bloodstream, removing harmful LDL, or bad cholesterol, and escorting it to the liver where it is broken down and excreted," Davey says.

Low-density lipoprotein is the "bad" cholesterol. If a doctor or other professional ever said they were concerned about your "high cholesterol" or bad cholesterol levels, they were likely referring to this number being high. LDL "accumulates into plaques in the blood vessels, blocking blood and oxygen from getting to the heart and brain, leading to heart attack and stroke," Davey says. 

HDL cholesterol plays an important role in repairing damage in your blood vessels. "Damage to the inner walls, from smoking, high blood pressure and chronically high blood sugar, is the first step in the disease process of atherosclerosis (plaque buildup in the artery walls). Damaged blood vessels act as a collection spot for LDL cholesterol, which forms a plaque. HDL cholesterol is used to patch damaged blood vessels, allowing them to heal," Davey says.

When you ask your doctor to check your cholesterol, there are three numbers you'll see on the lab report. First is total cholesterol, which is considered healthy if it is under 200. LDL should be less than 100 ideally, but if it is up toward 129, there may be concern depending on other risk factors. HDL should be 60 or higher, and if it is under 40 you are considered to be at significant risk for heart disease.

What causes high levels of LDL?

So how does LDL get high in the first place? Oftentimes diet is a major culprit, specifically a diet rich in saturated fat, trans fats and simple or processed carbohydrates, according to Harvard Health. Some people may also have a genetic predisposition to have high LDL cholesterol, and also some types of medications can play a role.

"Foods high in dietary cholesterol have very little impact on blood cholesterol levels in most people," Davey says. So now in light of recent research, it's more likely that other factors, like eating a diet in processed carbs, or smoking is contributing to high LDL levels, rather than the fact that someone eats egg yolks.

Davies says if you are obese or overweight, you are more likely to have high LDL cholesterol.

"Being overweight or obese increases the amount of LDL cholesterol your liver makes. It also decreases clearance of LDL cholesterol from your blood. Inflammation throughout the body is a common complication of obesity, inciting the liver to make more LDL cholesterol than is needed for a healthy body," Davey says. 

In addition to obesity, some diseases like diabetes, liver or kidney disease, PCOS or underactive thyroid can make you more susceptible to high cholesterol. "The current thinking is that inflammation caused by these disease states incites the liver to produce more LDL cholesterol than is needed," Davey says.


Avocados are rich in monounsaturated fats, which is a type of fat experts say is good for your health.

Getty Images

How to improve cholesterol levels 

"If your cholesterol is out of balance, lifestyle interventions are the first line of treatment," Davey says. Of course, you should see your doctor first and follow their guidance. But if you're looking for more information on what you can do, below are the main lifestyle factors you can try that science shows can improve your cholesterol levels.

Dietary changes

  • Eat more monounsaturated fats: "A diet high in monounsaturated fats, like olive oil, nuts and avocados, reduces harmful LDL and increases healthy HDL cholesterol" Davey says
  • Add omega-3 fats to your diet: "Research shows that consuming omega-3 fats, from fatty fish like salmon and tuna or a dietary supplement, can reduce LDL  cholesterol," Davey says.
  • Cut out partially hydrogenated oils, which contain trans fats: "Studies show that trans fats are thought to be responsible for up to 8% of the deaths from heart disease worldwide," Davey says.
  • Eat more fiber: "Fiber is the favorite food of the healthy bacteria in the gut. Well-fed and highly functioning gut bacteria will reduce LDL cholesterol, in the blood. Some of the best sources of soluble fiber include beans, peas and lentils, fruit, oats and whole grains. Fiber supplements like psyllium are also safe and inexpensive," Davey says.

Other lifestyle changes:

  • Exercise: "Exercise not only improves physical fitness and helps combat obesity, but it also reduces harmful LDL and increases beneficial HDL. Studies show that 30 minutes of moderate physical activity five days a week is enough to improve cholesterol and reduce the risk of heart disease," Davey says.
  • Lose weight if you are overweight or obese: "Weight loss has a double benefit on cholesterol by increasing beneficial HDL and decreasing harmful LDL," Davey says.
  • Quit smoking: "A lesser known reason to avoid smoking is that the immune cells in tobacco smokers are unable to return cholesterol from vessel walls to the blood for transport to the liver for excretion. This means that LDL cholesterol is allowed to remain in the vessels, forming plaques and leading to vessel stiffening and obstruction of the transport of blood and oxygen to the heart and brain," Davey says. 
Watch this: Telehealth will be the new normal after the pandemic
The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.