What Is Cholesterol?

It's a waxy substance found in every cell of your body. You use it to make vitamin D and hormones like testosterone and estrogen. It also helps digest food.

Your liver makes cholesterol. Your diet also affects your cholesterol level.

Cholesterol travels through your bloodstream in the form of tiny particles called lipoproteins. Low-density lipoprotein (LDL) brings cholesterol to cells throughout your body. It’s known as "bad" cholesterol because it can help plaque build up in your arteries. This can make you more likely to have a stroke or heart attack. High-density lipoprotein (HDL), called "good" cholesterol, takes cholesterol back to the liver, where it's prepped to leave your body.

Why Do Doctors Track It?

If you have too much cholesterol in your bloodstream, it can stick to your artery walls, forming plaque. This is known as atherosclerosis, and it can partially or completely block blood flow, leading to problems such as angina or a mini-stroke. It can also make plaque more likely to rupture, leading to a clot that then blocks an artery, which can cause a heart attack and stroke.

Atherosclerosis can take years to progress, and you may not have any symptoms until it's serious. That's why doctors recommend that once you reach the age of 20, you have your cholesterol levels tested at least every 4-6 years.

You have high cholesterol if your LDL is 160 or above and your total cholesterol is 240 or above. (Total cholesterol is calculated using a formula: HDL levels + LDL levels + 20% of your triglyceride levels.) Having low HDL cholesterol -- less than 40 -- is also a risk factor.

Keep in mind that your cholesterol levels are only part of the picture when it comes to heart health. Obesity, high blood pressure, diabetes, and smoking are all linked to artery disease, too.

"Many different factors go into whether or not someone will develop heart disease, like genes, habits, and environment," says Karol Watson, MD, PhD, co-director of the UCLA Program in Preventive Cardiology, a professor of medicine/cardiology at the David Geffen School of Medicine at UCLA, and the director of the UCLA Barbra Streisand Women's Heart Health Program.

You might hear about rare exceptions. Some people with high cholesterol and unhealthy lifestyles never have heart disease. But these cases don't mean you can dismiss your own high LDL levels, high blood pressure, smoking, or diabetes, says Jorge Plutzky, MD, director of preventive cardiology at Brigham and Women's Hospital/Harvard Medical School. Know that they can make you much more likely to have heart attacks and strokes.

High cholesterol can run in families. And for most people, cholesterol levels rise steadily from age 20 to 65. But while you can't change your genes or your age, there are many things you can do to keep your cholesterol levels in check. For example, exercise regularly. (Being inactive can lower your HDL levels.) And if you're overweight, you're more likely to have higher LDL and lower HDL. Smoking also lowers your HDL levels and raises your LDL levels. Plus, "Our bodies use dietary saturated fat to make cholesterol," Watson says.

LDL: Does Size Matter?

In recent years, there's been some buzz about how the size of your LDL particles matters, with small particles being worse than larger ones. The theory is that smaller LDL particles "can get into the artery wall more easily," Plutzky says. "Then, once there, they're more prone to undergo changes that can cause heart attacks and strokes."

Still, Plutzky notes that "for the average person, size of particles is not a definitive issue" and you probably don’t need to concern yourself with it. Watson agrees. "The smaller the particle, the worse it probably is, but even large, fluffy LDL is bad. All LDL is bad," she says.

When Meds Might Help

A healthy lifestyle is key. Some people also need medication. The most common cholesterol-lowering drugs are statins, and they can slash your risk of a heart attack or stroke. There are four groups of people who are candidates for statins:

  • Those with LDL levels of 190 or higher
  • Anyone who has had a cardiovascular event (like a heart attack or stroke) before
  • Those with diabetes
  • Anyone who, based on calculations, has a high risk of having a cardiovascular “event” (such as a heart attack) in the next 10 years.

If you meet any of these criteria, it's not a good idea to delay treatment while you try making lifestyle changes first, Plutzky says. "It's not either-or. You can still make lifestyle changes," he says. But the statins will help bring down your numbers, "and extensive studies have shown them to be safe and well-tolerated."

If you have low levels of HDL (“good” cholesterol), you should know that "none of the drugs that raise HDL have ever been shown to lower heart disease rates," Watson says. "So recommendations for raising HDL are to maintain a healthy weight, eat a Mediterranean-like diet, and exercise regularly."

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