Decoding the True Meaning Behind Your Cholesterol Levels

In the past, LDL was often referred to as the 'bad cholesterol,' while HDL was dubbed the 'good cholesterol.' This simplified explanation was what I was taught during my graduate studies in lipidology 13 years ago. However, scientific understanding has advanced since then. For instance, high HDL levels are no longer universally considered beneficial. Let’s delve into what your cholesterol numbers truly signify.

Typically, these numbers are obtained through a lipid panel, which provides a detailed breakdown of your total cholesterol, LDL, HDL, and triglycerides. Depending on the results, your doctor might congratulate you or suggest significant lifestyle adjustments and possibly prescribe cholesterol-lowering medications. According to the American Heart Association, it’s recommended to have your lipids checked at least every five years, or more often if your results raise any concerns.

A lipid panel is a key tool doctors use to monitor your risk of atherosclerosis, a condition where fatty plaques build up in artery walls, causing them to narrow and harden. This increases the likelihood of plaque or blood clots obstructing blood flow. Such blockages can cause damage anywhere in the body. If it occurs in a coronary artery of the heart, it can lead to a heart attack. If it happens in the brain, it can result in a stroke.

Atherosclerosis is influenced by the levels of cholesterol and triglycerides (fats) in your bloodstream. A lipid panel acts as a diagnostic tool, offering insights into the amount of cholesterol present and its activity.

Total Cholesterol Isn’t the Key Focus

Cholesterol has unfairly gained a negative reputation, despite being a crucial molecule in the human body. It plays a role in forming cell membranes, is a part of bile (essential for digesting fats), and serves as a building block for vitamin D and hormones like cortisol, estrogen, and testosterone.

Although cholesterol is vital, it doesn’t necessitate excessive consumption. In fact, our bodies can produce all the cholesterol we require, making dietary intake unnecessary. However, unless you follow a vegan diet, cholesterol is naturally present in animal-based foods such as meat, fish, eggs, milk, and butter. For years, U.S. dietary guidelines advised limiting cholesterol intake, but recent research shows that dietary cholesterol has minimal impact on blood cholesterol levels, as the body adjusts its production accordingly. The latest Dietary Guidelines for Americans no longer set a limit on dietary cholesterol. (They do, however, recommend reducing saturated fats, which are abundant in most animal fats, with eggs and fish being exceptions.)

Your lipid panel results will include a total cholesterol value, but this figure alone isn’t particularly meaningful. On its website, the American Heart Association (AHA) no longer provides a standard range for total cholesterol, stating, “These ranges are no longer used. Instead, total cholesterol levels are evaluated alongside other risk factors, and treatment recommendations are made based on the overall picture.”

Historically, a total cholesterol level below 200 mg/dL has been viewed as healthy. Dr. Ali Rahimi, a cardiologist at Kaiser Permanente in Atlanta, still prefers to see total cholesterol remain under this threshold.

However, what matters more than total cholesterol is how it’s distributed and where it’s transported in the body. This leads us to LDL and HDL, two types of lipoproteins. These act as carriers, moving cholesterol and other lipids through the bloodstream, but they serve distinct roles and have differing impacts on health.

The bottom line: While a total cholesterol level below 200 mg/dL is ideal, this number alone isn’t the most critical. The other values in your lipid report are far more significant for assessing your health.

LDL Is Problematic

LDL particles carry cholesterol, as their primary role is to transport it from the liver to cells throughout the body. While this is a vital function, excessive LDL in the bloodstream can contribute to atherosclerosis, earning it the label of “bad cholesterol.” This reputation is justified, as individuals with high LDL levels face a greater risk of developing atherosclerosis and heart disease. Reducing LDL through medication (often statins) or lifestyle adjustments can significantly lower this risk.

Your lab results or doctor will likely indicate that LDL should be under 130 mg/dL. However, cardiologists now interpret this value more flexibly than they did five years ago. “Previously, we strictly focused on hitting specific numbers, believing lower was always better, and initiated drug therapy at certain thresholds,” explained Rahimi.

An LDL level exceeding 190 mg/dL is classified as very high, and the AHA recommends statin treatment regardless of other factors. For levels below this, the AHA treats LDL as one of several risk factors, including smoking, diabetes, high blood pressure, and a family history of early coronary heart disease. These factors can elevate your heart disease risk and may influence the decision to start medication. Discuss these with your doctor, or use this online calculator to assess your risk. (Note: This calculator and similar tools require users to be at least 40, as the underlying equations aren’t validated for younger individuals. If you’re under 40, input 40 but be aware the estimate may be less accurate. Risk calculators from Mayo Clinic and Kaiser allow younger ages, though their reliability for younger users remains uncertain.)

Rahimi emphasizes that an LDL level below 130 mg/dL is ideal. For those with levels between 130 and 190, the decision to prescribe medication depends on additional risk factors. Regardless, individuals in this range can benefit from quitting smoking, increasing physical activity, and improving their diet. Rahimi prefers starting with these lifestyle changes, which can lower LDL by up to 30 mg/dL—a significant improvement, whether or not medication is eventually needed.

The bottom line: LDL remains the “bad” cholesterol, and a desirable level is below 130 mg/dL. Both lifestyle modifications and medications can be effective, and if your LDL exceeds 190 mg/dL, medication is highly likely to be recommended.

HDL Isn’t as Beneficial as Once Believed

HDL has traditionally been viewed favorably. It helps remove excess cholesterol from the body, including from arterial plaques, and transports it back to the liver for processing. Individuals with lower HDL levels often face a higher risk of cardiovascular disease, leading to the assumption that higher HDL is better. (Historically, a healthy HDL level is considered 40 mg/dL or above for men and 50 mg/dL or above for women.)

However, recent scientific findings have been surprising. Several drugs designed to increase HDL were expected to reduce heart disease risk, but they failed in clinical trials. (Some even caused more harm than good.) Additionally, genetic studies have shown that having genes associated with higher HDL doesn’t necessarily lower the risk of heart disease.

“That’s been a major revelation in cardiology,” said Rahimi. “We’ve had to reconsider [HDL], and rather than being a direct cause, it might simply be a related factor.”

In simpler terms, having very high HDL doesn’t necessarily guarantee a lower risk of heart disease. This is because certain genetic factors can lead to high HDL levels where the HDL doesn’t function correctly.

Similarly, low HDL might indicate a higher risk of heart disease, but it’s unlikely to be the direct cause. “It’s more of a marker,” explained Rahimi. “Individuals with low HDL are often less active, may smoke, or have insulin resistance,” so doctors may focus on addressing these underlying issues rather than solely aiming to increase HDL.

“The traditional idea of ‘good cholesterol, bad cholesterol’ is no longer valid,” said Rahimi.

HDL remains a key focus of ongoing research. Scientists are exploring ways to measure different HDL subtypes to determine if some are more beneficial than others. In the future, genetic testing might also help us better understand and interpret lipid panel results.

The bottom line: Currently, HDL is likely not a particularly meaningful number.

Triglycerides Also Provide Important Insights

The final value on your lipid panel is triglycerides. Normal levels are below 150 mg/dL, and higher levels are linked to an increased risk of heart disease. (Unlike HDL, this connection has been supported by genetic studies, though triglycerides have been studied less extensively.) Rahimi notes that medications are typically considered only when triglyceride levels exceed 500 mg/dL. (Drugs like statins, fibrates, niacin, and high-dose fish oil may be used.) For levels between 150 and 500, lifestyle changes are recommended to reduce triglycerides.

“Elevated triglyceride levels often raise concerns about dietary habits,” said Rahimi. High carbohydrate consumption, particularly sugar, is a major contributor. Other factors include obesity, insulin resistance (which can lead to diabetes), and excessive alcohol consumption.

The bottom line: Aim to keep triglycerides under 150 mg/dL through dietary adjustments. If levels surpass 500 mg/dL, medication is likely necessary.

Small Numbers, Significant Impact

The lipid panel continues to be a key tool for evaluating heart disease risk. These values are advantageous because they are measurable and can be monitored over time. However, they also have their limitations. Certain lipid metrics are more meaningful than others, and none operate in isolation. They are influenced by a variety of factors, some within your control and others, like genetics, that are not. Our understanding of these values is still evolving, and it was perhaps overly simplistic to categorize cholesterol as simply “good” or “bad.”

NOTE: This article was revised on 4/4/18 to add details about age requirements for cardiac risk calculators [12:47 pm EDT] and to clarify that extremely high HDL, linked to specific genetic conditions, may not correlate with a reduced risk of heart disease [6:38 pm EDT].