To understand how cholesterol — good or bad, high blood levels or not — affects your health, you must first know what cholesterol actually is.
Cholesterol is a fatty, waxlike substance found naturally in all the cells of your body. Your body needs cholesterol to manufacture hormones and synthesize vitamin D, among other functions.
According to the American Heart Association (AHA), your body manufactures all the cholesterol it needs in your liver. But you can also get cholesterol in the foods you eat. Dietary sources of cholesterol are primarily animal products and include:
- Meat
- Eggs
- Full-fat dairy
- Palm, palm kernel, and coconut oils.
These foods contain dietary cholesterol. However, foods high in saturated fat and foods with trans fats trigger the liver to make more cholesterol and represent a major source for increasing blood cholesterol. Because the typical Western diet is loaded with these foods, rising cholesterol levels have led the way to an epidemic of health problems linked to high blood cholesterol, says Jorge Trejo Gutierrez, MD, a cardiologist with the Mayo Clinic in Jacksonville, Florida.
Though some experts dispute the direct link between high blood cholesterol levels and cardiovascular disease (CVD), major organizations like the American Heart Associationand the National Heart, Lung, and Blood Institute (part of the National Institutes of Health) maintain that high blood cholesterol levels play a role in the development of conditions such as heart attack, stroke, and peripheral artery disease (narrowing of arteries in your extremities). Experts are also clear on the fact that high blood cholesterol increases your risk for heart disease when combined with other proven risk factors, such as type 2 diabetes, high blood pressure, smoking, and a family history of cardiovascular disease.
Types of Cholesterol and How They Work in Your Body
Cholesterol is carried through the circulatory system on lipoproteins, small “packages” made up of protein on the inside and fat on the outside. There are two primary subtypes of lipoproteins: high-density lipoproteins (HDL) and low-density lipoproteins (LDL).
HDL has been labeled “good” cholesterol because these lipoproteins travel around the body and “pick up” excess fat in the form of LDL cholesterol and take it to the liver, where it can be broken down and removed from the body.
LDL is termed “bad” cholesterol because when there is too much of it circulating in the blood (more than the good HDL scavengers can scoop up and ferry away), it can eventually build up in the form of plaque on the walls of your arteries. This is called atherosclerosis. Over time, plaque accumulation impedes healthy blood flow to the heart and raises the risk for heart attack, stroke, and peripheral artery disease.
Another type of fat in the blood occurs as triglycerides. Triglycerides are a form of fat (not a combination of fat and protein, as HDL and LDL are), and they also circulate through the body, holding on to energy, or calories, you take in via the foods you eat. A high triglyceride level makes a high LDL level worse in terms of how much fatty buildup you have on your artery walls.
Why Are Some People More Likely to Have High Cholesterol Than Others?
Understanding why some people have high cholesterol numbers and others don’t isn’t as simple as it might seem. For example, while it’s more likely that an overweight or obese person’s cholesterol will be at an unhealthy level, it’s also true that many thin people have high cholesterol. Here are some factors that affect your cholesterol levels:
- Heredity: Though this is relatively rare, a condition called familial hypercholesterolemia (FH) may make some people genetically prone to high levels of bad cholesterol. There are two types: heterozygous, in which a person has the inherited gene from one parent only; and homozygous, in which the person has two copies of the gene, one from each parent.
- Homozygous is both more rare and more dangerous. People with FH don’t recycle LDL cholesterol as effectively and end up with high levels of this type of cholesterol, which makes them more prone to atherosclerosis, often starting at far younger ages. If you have FH or if you have a parent or sibling who had a heart attack early in life, it’s recommended that you begin cholesterol tests early. (The majority of FH patients need cholesterol-lowering drugs such as a statin to keep their cholesterol numbers in a healthy range.)
- Smoking: While smoking doesn’t directly cause high cholesterol, it is by itself a major proven risk for heart disease and stroke. That risk rises if you also have high LDL cholesterol levels. One reason is that smoking lowers your levels of HDL, helping to diminish or erase that form of cholesterol’s protective effect. Quitting smoking has immediate benefits on your heart health. A research review published in 2013 in the journal Biomarker Research found that HDL levels increase almost immediately in people who quit smoking.
- Diet: What you eat certainly plays a very important role in your heart health, but it’s not as simple as avoiding fat. Instead, eliminate processed foods that contain trans fats (listed on labels as hydrogenated or partially hydrogenated oils). Also limit intake of saturated fats, which come mainly from animal products. Instead, up your intake of unsaturated fats, like those found in avocado, nuts, seeds, and olive oil. As a general rule, says Dr. Gutierrez, “consume a diet based mostly on whole, plant-based foods and is low in saturated and animal fats.”
RELATED: 10 Things You Need to Know About Inherited High Cholesterol
Getting Tested: What Do Blood Cholesterol Test Results Mean?
The American Heart Association recommends that all Americans over age 20 get their cholesterol levels tested, generally with a lipid panel, every four to six years. Your doctor may recommend getting your cholesterol tested more frequently in middle age because your overall risk for heart disease starts to rise. Your doctor might also order this test if you already have other risk factors such as diabetes or high blood pressure. You might also have more frequent tests if you’re already on a cholesterol-lowering medication such as a statin (so your doctor can assess how well it’s working), or if you’re trying to lower your cholesterol levels via diet.
It’s important to have a fasting blood test, which means you shouldn’t eat or drink anything (except water) for 9 to 12 hours before your blood is drawn. A fasting test is more accurate specifically for triglyceride levels, because triglycerides tend to remain elevated for several hours after a meal. Results will be listed as levels of total cholesterol, HDL, LDL, and triglycerides in milligrams per deciliter of blood, or mg/dl.
Here’s what the test will reveal:
- Total blood cholesterol: Think of this as your overall “score.” This number is the result of a calculation that adds up HDL and LDL levels, plus 20 percent of your triglyceride level. Although stated guidelines point to a total cholesterol of 200 mg/dl or less as “desirable” and anything over 239 mg/dl as “high,” this number is less meaningful than it might appear, says Barbara Roberts, MD, a clinical associate professor of cardiology at Brown University in Providence, Rhode Island, and former director of the Women’s Cardiac Center at The Miriam Hospital. She adds that what’s important is the ratio of good to bad cholesterol.
- HDL cholesterol: You want this number to be higher, as a high HDL level is linked with good heart health. An HDL level of 60 mg/dl or higher appears to be protective against heart disease. In contrast, a level of less than 40 mg/dl appears to be non-protective and may be harmful.
- LDL cholesterol: An LDL of less than 100 mg/dl is the holy grail; a number 129 mg/dl or lower is also good. A range of 130 to 159 mg/dl is borderline high, 160 to 189 mg/dl is high, and above 190 mg/dl is in the danger zone.
- Triglycerides: Normal levels of triglycerides vary by gender and age. High triglycerides are linked to being overweight or obese, being sedentary, smoking, drinking alcohol in excess, and consuming a high-carbohydrate diet. A normal level is 150 mg/dl; if your level is approaching 200 mg/dl, that is borderline high; and anything over 200 mg/dl is high and leaves you at greater risk for cardiovascular disease.
Facts About Cholesterol-Lowering Medication
If you and your doctor feel it would be wise to lower your cholesterol levels, you may be prescribed a statin drug. Guidelines put out by the AHA and the American College of Cardiologist in 2013 say that the decision to start statin therapy should be based on a calculation of your risk for cardiovascular disease over 10 years. (See the risk calculatorhere.)
Cholesterol numbers, says Gutierrez, are only part of the picture, “though the most current recommendations say that in the presence of diabetes you should start medication when LDL is higher than 70 mg/dl.”
He also points out that it’s important to first try making lifestyle changes, such as:
- Consuming a healthier diet
- Exercising
- Quitting smoking
- Getting blood pressure under control
It’s also important to note that those lifestyle changes should not be abandoned just because you’re taking medication.
Statin drugs work in two ways, says Gutierrez. “They block the enzyme that helps you produce cholesterol in the liver, and they activate the receptors for LDL in your liver cells, so that more cholesterol is ‘captured’ from your blood.”
In addition to statin drugs, a new class of cholesterol-lowering drugs called PCSK9 inhibitors have recently become available. These are monoclonal antibodies that work to inactivate a protein in the liver called proprotein convertase subtilisin kexin 9 (PCSK9), reducing the amount of LDL circulating in your body. (Interestingly, says Gutierrez, researchers discovered PCSK9 in people with an extremely rare genetic condition called hypocholesterolemia, who naturally have very low LDL levels and nearly no heart disease.) For now, PCSK9 inhibitors, injectable drugs, are still very expensive. It was approved by the Food and Drug Administration in 2015 to treat people with familial hypercholesterolemia.
Cholesterol and Heart Disease: Understanding the Connection
For years, it had been believed that there’s more or less a straight line between cholesterol and heart disease—but recent research suggests that this relationship may be more complex.
A 2017 Minneapolis Heart Foundation study, published in the Journal of the American Heart Association, found that many people who have heart attacks don’t have high cholesterol. “The link between cholesterol and heart disease is weak,” says Dr. Roberts, who places a large portion of the blame for the persistence of that link on pharmaceutical advertising for statin drugs. “Statins do lower cholesterol levels,” she says, “but atherosclerosis still progresses” due to factors like age, poor diet, smoking, and so on.
In addition, a 2015 review of studies of cholesterol and cardiovascular disease published in the American Journal of Clinical Nutrition found that no rigorous connection could be drawn between dietary cholesterol intake and the risk of CVD — and suggested that such studies are warranted.
In contrast, the results of long-term research, published in September 2017 in the journal Circulation, concluded that statin use in men with high LDL cholesterol who had no other risk factors for heart disease had lower rates of heart disease by more than 28 percent over 20 years.
When it comes to heart health, your biggest risk factor is age, says Roberts.
To keep your risk of high cholesterol as low as possible and your heart as healthy as you can for as long as you can, eat real (unprocessed) food, exercise regularly, don't smoke, and keep your blood pressure under control.
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