Low-density lipoprotein (LDL) cholesterol, or “bad” cholesterol, collects in the walls of the blood vessels, causing them to narrow. High-density lipoprotein (HDL), or “good” cholesterol, moves LDL cholesterol out of the bloodstream.

The two main types of cholesterol are high-density lipoprotein (HDL) or “good” cholesterol, and low-density lipoprotein (LDL) or “bad” cholesterol. Some cholesterol is needed in the body, but high levels can be dangerous.

Along with smoking and high blood pressure, raised blood cholesterol is one of the main risk factors for heart disease. People can reduce their blood cholesterol with a healthful diet, exercise, and medication.

In this article, we look at HDL and LDL in detail, including what makes one good and the other bad, as well as what a person can do to keep levels in check.

A doctor selecting HDL over LDL cholesterolShare on Pinterest
HDL cholesterol can move LDL cholesterol from the blood.

LDL cholesterol is often called bad cholesterol. If there is too much LDL cholesterol in the blood, it builds up in the walls of the blood vessels, causing them to narrow and stiffen.

A buildup of LDL cholesterol reduces blood flow and can increase the risk of heart attack or stroke.

HDL or good cholesterol can move LDL cholesterol from the blood to the liver, which breaks it down for disposal as waste. HDL cholesterol is referred to as good cholesterol because it reduces the level of cholesterol in the blood.

Higher HDL levels are linked to a reduced risk of heart attack and heart disease.

In the United States, cholesterol is measured in milligrams per deciliter (mg/dL). The guidelines for healthy cholesterol levels are as follows:

  • total cholesterol below 200 mg/dL
  • LDL cholesterol less than 100 mg/dL
  • HDL cholesterol above 40 mg/dL

Different regions and countries may have varying guidelines, so it is wise to speak to a doctor about the most accurate and up-to-date ranges.

The total cholesterol to HDL cholesterol ratio can help a person know if they are consuming enough good cholesterol and to limit sources of bad cholesterol. It can be measured by dividing the total cholesterol by the HDL level.

Ideally, the ratio should be below 4. The lower this number is, the healthier a person’s cholesterol levels are.

Total cholesterol does fluctuate, so more than one blood test might be required for an accurate assessment. Levels can change following a meal, so sometimes a blood test will be taken first thing in the morning before a person has breakfast.

Studies suggest that the total cholesterol to HDL ratio is a better marker of the risk of heart disease than LDL cholesterol levels alone.

Non-HDL cholesterol

Another method of assessing cholesterol levels is calculating a non-HDL cholesterol level. This is measured by subtracting HDL cholesterol from the total cholesterol.

This method is considered to be more accurate by some doctors because it includes very low-density lipoprotein (VLDL) levels in the calculation.

Similarly to LDL cholesterol, VLDL cholesterol can also build up inside the walls of blood vessels, which is undesirable.

Ideally, a non-HDL cholesterol level should be less than 130 mg/dL. A higher value than that increases the risk for heart disease.

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High LDL cholesterol may be caused by inactivity.

Causes of high LDL cholesterol include:

  • Eating a diet high in saturated fat: Diets high in saturated and hydrogenated fats can increase LDL cholesterol levels.
  • Inactivity: Not getting enough exercise can lead to weight gain, which is linked to increased cholesterol levels.
  • Obesity: People who are overweight have an increased risk of high cholesterol levels.
  • Smoking: A chemical in cigarettes lowers HDL cholesterol levels and damages the lining of blood vessels, which can increase the risk of hardening of the arteries.
  • Medical conditions: Some of these that can affect LDL cholesterol levels include type 2 diabetes, underactive thyroid, kidney or liver conditions, and alcohol addiction.
  • Menopause: For some women, cholesterol levels can rise after menopause.
  • Genetics: Familial hypercholesterolemia (FH) is an inherited form of high cholesterol that puts people at risk of early heart disease.

The following lifestyle changes can help lower LDL cholesterol:

Some studies have shown vitamin B-3 can lower LDL cholesterol while raising HDL. It is important to talk to a doctor before taking niacin supplements.

People trying to lower their LDL cholesterol should also avoid eating saturated and trans fats. Foods to avoid are:

  • cakes, cookies, and pastries
  • frozen ready meals, such as frozen pizza
  • margarine
  • fried fast foods
  • cream-filled candies
  • donuts
  • ice cream
  • packaged puddings
  • pre-made breakfast sandwiches
  • potato chips

Other diet tips to prevent LDL levels creeping up include:

  • Switch fat sources: Swap saturated fats for nut and seed oils or monounsaturated fats from olive, avocado, and canola oil.
  • Increase fiber intake: A diet high in fiber is believed to be good for total blood cholesterol levels. Soluble fiber found in fruits, vegetables, and oats is particularly beneficial.
  • Eat more garlic: Garlic is rich in compounds that can help lower blood cholesterol. The beneficial effects are only felt if garlic is regularly consumed for more than 2 months.

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HDL cholesterol levels may be improved by eating oily fish, such as mackerel.

A variety of things can improve HDL cholesterol levels, including:

  • Omega-3 fatty acids: Omega-3 fatty acids can lower blood cholesterol when consumed as part of a balanced diet. The highest levels of omega-3 fatty acids are in oily fish, such as mackerel, trout, herring, sardines, fresh tuna, salmon, and halibut. Studies suggest eating 2–3 portions of oily fish each week can increase HDL levels in the blood.
  • Brightly-colored fruit and vegetables: The antioxidants in brightly colored fruit and vegetables have been shown to improve HDL cholesterol levels.
  • Regular exercise: Research shows that exercise and physical activity can raise HDL levels.

High LDL cholesterol is a risk factor for heart disease, but it can often occur without any symptoms.

It is recommended that people over 40 years of age arrange a blood test to check their cholesterol levels and total cholesterol to HDL ratio.

Dietary and lifestyle changes can make a big difference to HDL and LDL levels. If they do not improve with these changes, a doctor may recommend medications.