What Is Cholesterol? How It Works, Foods to Avoid, and the Truth About HDL

Cholesterol is a waxy type of lipid found in almost every cell of the body. A building block of animal life, cholesterol helps form cell membranes and plays a key role in the production of hormones, vitamin D, skin oils, and digestive acids.

The liver makes all the cholesterol that the body needs. Some factors can cause excessive levels of cholesterol to enter the bloodstream; over time, this can seriously impair our cardiovascular systems.

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Cholesterol is not water-soluble, meaning it can’t travel through the bloodstream on its own. For transport, it gets bundled with particles called lipoproteins. The main types of lipoproteins that carry cholesterol are low-density lipoproteins (LDL) and high-density lipoproteins (HDL).

Like cholesterol, triglycerides are a type of fatty acid that come from our liver and from the foods we eat. They, too, get bundled with lipoproteins and carried through the body so cells can extract the fat and protein for use. When we consume more calories than we need, we take in excess triglycerides, which our body stores as fat. Because elevated triglycerides can contribute to atherosclerosis, triglyceride levels are typically measured alongside LDL and HDL cholesterol. Lifestyle measures aimed at reducing LDL cholesterol can also bring down triglycerides.

For most people, high cholesterol is primarily lifestyle-related, the American Heart Association notes. Lifestyle factors that drive up LDL cholesterol (or decrease HDL cholesterol) include:

Genes play a role in the amount of cholesterol that your liver produces. Familial hypercholesterolemia, an inherited genetic condition, impacts an estimated .05% of the population. Genetics can also influence cholesterol levels in indirect ways, such as by predisposing someone to be overweight.

Having Type 2 diabetes is a risk factor for high cholesterol, though more research is needed to understand the connection.

Among the lifestyle factors that can influence LDL cholesterol levels, diet plays a major role.

“Studies have shown that one of the strongest contributors to our blood levels of cholesterol, from a dietary standpoint, is our intake of saturated fat, which is found predominantly in animal products, particularly red meat (processed and unprocessed) and dairy.” Harkin adds that palm oil and coconut oil, which are found in many highly processed foods, are also high in saturated fat.

Trans fats also drive up cholesterol levels. Historically, these fats could be found in the form of partially hydrogenated oils in margarine, shortening, butter, cakes, cookies, and salty snack foods. In 2018, the Food and Drug Administration banned manufacturers from using trans fats, but these fats may still occur in deep-fried foods due to the extreme temperature at which oils are heated.

There’s been some debate about the degree to which dietary cholesterol raises blood cholesterol levels. Because foods high in cholesterol are also typically high in saturated fat, it’s difficult to tease apart the effects of each.

However, a large 2019 study looked for associations between the consumption of cholesterol and rates of cardiovascular disease in 29,615 participants over a median of 17.5 years. They found that, independent of fat and overall diet quality, higher cholesterol intake was in fact associated with a higher risk of CVD. They identified a dose-response relationship: For every additional 300 milligrams of cholesterol consumed daily, there was a 17% increase in the risk of CVD and 18% increase in the risk of death from all causes. (For reference, a single egg contains around 180 milligrams of cholesterol.)

The easiest way to keep cholesterol out of your diet is to steer clear of animal products. All animals produce cholesterol in their livers, so when we eat other animals or animal-based products, we consume their cholesterol. (This is why, when checking nutrition labels, the presence of any cholesterol is a telltale sign that an item isn’t vegan—though the absence of it doesn’t guarantee that a product is vegan.)

Ranges for “normal” cholesterol levels vary based on age, sex, and medical history, but according to the Mayo Clinic, adults age 20 and older should aim for the following numbers.

Source: Mayo Clinic

Source: Mayo Clinic

Source: Mayo Clinic

*Note: There is some debate about whether HDL cholesterol in excess of 60 mg/dL is truly beneficial. LDL cholesterol levels may be a more reliable indicator of cardiovascular health. 

For more detailed information about normal cholesterol levels, see the American Heart Association and American College of Cardiology guidelines for clinicians.

The primary complication arising from high cholesterol is cardiovascular disease, including coronary artery disease, stroke, and myocardial infarction (heart attack). Strokes and heart attacks follow a similar chain of events: An arterial plaque ruptures. A blood clot forms on the ruptured plaque. The blood clot completely blocks blood from flowing through the artery, preventing blood from getting to the brain (in the case of stroke) or the heart (in the case of heart attack).

High cholesterol and resulting atherosclerosis may contribute to high blood pressure, as the heart has to work harder to pump blood through constricted, plaque-laden blood vessels.

In addition to cardiovascular complications, a number of studies suggest that high cholesterol may impair insulin sensitivity, leading to insulin resistance. Insulin resistance significantly increases the risk of several chronic diseases including Type 2 diabetes, fatty liver disease, chronic kidney disease, and Alzheimer’s disease.

For patients with extremely high cholesterol and/or established cardiovascular disease, lipid-lowering medications, such as statins, may be necessary. For many people, lifestyle modifications alone may be enough to bring cholesterol down into the healthy range.

“For the vast majority of patients who have elevated cholesterol and who do not yet have heart disease, the first-line therapy is lifestyle modifications,” says Harkin. “That involves changes in diet, exercise, and all the other lifestyle factors, but diet [is] one of the biggest levers that we can pull.”

Forks Over Knives has heard from many readers over the years who have reduced their cholesterol after adopting a whole-food, plant-based lifestyle.

To learn more about a whole-food, plant-based diet, visit our Plant-Based Primer. For meal-planning support, check out Forks Meal Planner, FOK’s easy weekly meal-planning tool to keep you on a healthy plant-based path.