With all of the bad publicity cholesterol gets, people are often surprised to learn that it’s actually necessary for our existence.

What’s also surprising is that our bodies produce cholesterol naturally. But cholesterol isn’t all good, nor is it all bad — it’s a complex topic and one worth knowing more about.

Cholesterol is a substance made in the liver that’s vital to human life. You can also get cholesterol through foods. Since it can’t be created by plants, you can only find it in animal products like meat and dairy.

In our bodies, cholesterol serves three main purposes:

  1. It aids in the production of sex hormones.
  2. It’s a building block for human tissues.
  3. It assists in bile production in the liver.

These are important functions, all dependent on the presence of cholesterol. But too much of a good thing isn’t good at all.

When people talk about cholesterol, they often use the terms LDL and HDL. Both are lipoproteins, which are compounds made of fat and protein that are responsible for carrying cholesterol throughout the body in the blood.

LDL is low-density lipoprotein, often called “bad” cholesterol. HDL is high-density lipoprotein, or “good” cholesterol.

LDL is known as the “bad” cholesterol because too much of it can lead to hardening of the arteries.

According to the American Heart Association, LDL leads to plaque accumulation on the walls of your arteries. When this plaque builds up, it can cause two separate, and equally bad, issues.

First, it can narrow the blood vessels, straining the flow of oxygen-rich blood throughout the body. Second, it can lead to blood clots, which can break loose and block the flow of blood, causing a heart attack or stroke.

When it comes to your cholesterol numbers, your LDL is the one you want to keep low — ideally less than 100 milligrams per deciliter (mg/dL).

HDL helps keep your cardiovascular system healthy. It actually aids in the removal of LDL from the arteries.

It carries the bad cholesterol back to the liver, where it’s broken down and eliminated from the body.

High levels of HDL have also been shown to protect against stroke and heart attack, while low HDL has been shown to increase those risks.

According to the National Institutes of Health (NIH), HDL levels of 60 mg/dL and higher are considered protective, while those under 40 mg/dL are a risk factor for heart disease.

When you have your cholesterol checked, you’ll receive measurements for both your HDL and LDL, but also for your total cholesterol and triglycerides.

An ideal total cholesterol level is lower than 200 mg/dL. Anything between 200 and 239 mg/dL is borderline, and anything above 240 mg/dL is high.

Triglyceride is another type of fat in your blood. Like cholesterol, too much is a bad thing. But experts are still unclear on the specifics of these fats.

High triglycerides usually accompany high cholesterol and are associated with an increased risk of heart disease. But it isn’t clear if high triglycerides are a risk factor.

Doctors generally weigh the importance of your triglyceride count against other measurements like obesity, cholesterol levels, and more.

There are several things that influence your cholesterol numbers — some of which you have control over. While heredity may play a role, so too do diet, weight, and exercise.

Eating foods that are low in cholesterol and saturated fats, getting regular exercise, and managing your weight are all associated with lower cholesterol levels and lower risks of cardiovascular disease.