Cholesterol is both good and bad. At normal levels, it is an essential substance for the body. However, if concentrations in the blood get too high, it becomes a silent danger that puts people at risk of heart attack.

Cholesterol is present in every cell of the body and has important natural functions when it comes to digesting foods, producing hormones, and generating vitamin D. The body produces it, but people also consume it in food. It is waxy and fat-like in appearance.

There are two types of cholesterol:

• low-density lipoproteins (LDL), or "bad" cholesterol
• high-density lipoproteins (HDL), or "good" cholesterol

In this article, we will explain the role of cholesterol. We will also discuss the causes of high cholesterol, and its symptoms, treatment, and prevention.

Fast facts on cholesterol:

• Cholesterol is an essential substance that the body produces but which people also consume in foods.
• Risk factors for high cholesterol include family history and the modifiable lifestyle choices of diet and exercise.
• Having high cholesterol does not usually produce any symptoms.
• If lifestyle changes are unsuccessful or cholesterol levels are very high, a doctor may prescribe a lipid-lowering drug, such as a statin.

What is cholesterol?

Cholesterol is an oil-based substance. It does not mix with the blood, which is water-based.

It travels around the body in lipoproteins.

Two types of lipoprotein carry the parcels of cholesterol:

Low-density lipoprotein (LDL): Cholesterol that travels in this way is unhealthful or "bad" cholesterol.

High-density lipoprotein (HDL): Cholesterol that is present in HDL is known as "good" cholesterol.

Cholesterol has four primary functions, without which we could not survive.

These are:

• contributing to the structure of cell walls
• making up digestive bile acids in the intestine
• allowing the body to produce vitamin D
• enabling the body to make certain hormones

Causes of high cholesterol

High cholesterol is a significant risk factor for coronary heart disease and a cause of heart attacks.

A build-up of cholesterol is part of the process that narrows arteries, called atherosclerosis. In atherosclerosis, plaques form and cause restriction of blood flow.

Reducing the intake of fat in the diet helps to manage cholesterol levels. In particular, it is helpful to limit foods that contain:

• Cholesterol: This is present in animal foods, meat, and cheese.
• Saturated fat: This occurs in some meats, dairy products, chocolate, baked goods, deep-fried, and processed foods.
• Trans fats: This occurs in some fried and processed foods.

Excess weight or obesity can also lead to higher blood LDL levels. Genetic factors can contribute to high cholesterol. People with the inherited condition familial hypercholesterolemia have very high LDL levels.

Other conditions that can lead to high cholesterol levels, include:

• diabetes
• liver or kidney disease
• polycystic ovary syndrome
• pregnancy and other conditions that increase levels of female hormones
• underactive thyroid gland
• drugs that increase LDL cholesterol and decrease HDL cholesterol, such as progestins, anabolic steroids, and corticosteroids

High cholesterol symptoms

A person with high cholesterol levels often has no signs or symptoms, but routine screening and regular blood tests can help detect high levels.

A person who does not undergo testing may have a heart attack without warning, because they did not know that they had high cholesterol levels. Regular tests can help to reduce this risk.

Cholesterol in foods

A report from Harvard Health has identified 11 cholesterol-lowering foods that actively decrease cholesterol levels:

• oats
• barley and whole grains
• beans
• eggplant and okra
• nuts
• vegetable oil (canola, sunflower)
• fruits (mainly apples, grapes, strawberries, and citrus)
• soy and soy-based foods
• fatty fish (particularly salmon, tuna, and sardines)
• foods rich in fiber

Adding these to a balanced diet can help keep cholesterol in check.

The same report also lists foods that are bad for cholesterol levels. These include:

• red meat
• full-fat dairy
• margarine
• hydrogenated oils
• baked goods

Various low cholesterol recipe books are available to purchase online.

Levels and ranges

In adults, total cholesterol levels less than 200 milligrams per deciliter (mg/dL) are considered healthy.

• A reading between 200 and 239 mg/dL is borderline high.
• A reading of 240 mg/dL and above is considered high.

LDL cholesterol levels should be less than 100 mg/dL.

• 100–129 mg/dL is acceptable for people with no health problems but may be a concern for anyone with heart disease or heart disease risk factors.
• 130—159 mg/dL is borderline high.
• 160–189 mg/dL is high.
• 190 mg/dL or higher is considered very high.

HDL levels should be kept higher. The optimal reading for HDL levels is of 60 mg/dL or higher.

• A reading of less than 40 mg/dL can be a major risk factor for heart disease.
• A reading from 41 mg/dL to 59 mg/dL is borderline low.

Preventing high cholesterol

People who wish to reduce their cholesterol levels or maintain a suitable level can make four major lifestyle decisions.

• eat a heart-healthy diet
• regularly exercise
• avoid smoking
• achieve and maintain a healthy weight

These actions will reduce the risk of coronary heart disease and heart attack.

Since 2013, guidelines on reducing or preventing high cholesterol have focused on addressing lifestyle risks, even at a young age.

Since 2018, new guidelines published in the Journal of the American College of Cardiology also urged doctors also to discuss with individuals the following factors that may increase a person's risk:

• family history and ethnicity
• certain health conditions that increase the risk of high cholesterol, such as chronic kidney disease or chronic inflammatory conditions

Taking these factors into consideration will lead to a more personalized approach to the treatment and prevention of high cholesterol levels.

How can high cholesterol be treated?

There are a number of ways to treat high cholesterol; these include:

Lipid-lowering therapy

For a person with high cholesterol levels, drug treatment will depend on their cholesterol level and other risk factors.

Recommendatoins usually start with diet and exercise, but people with a higher risk of a heart attack may need to use statins or other medications.

Statins are the leading group of cholesterol-lowering drugs. The statins available on prescription in the United States include:

• atorvastatin (brand named Lipitor)
• fluvastatin (Lescol)
• lovastatin (Mevacor, Altoprev)
• pravastatin (Pravachol)
• rosuvastatin calcium (Crestor)
• simvastatin (Zocor)

Apart from statins, a doctor may prescribe:

• selective cholesterol absorption inhibitors
• resins
• fibrates
• niacin

In 2017, researchers noted that a new drug, ezetimibe, can significantly reduce the risk of a major cardiovascular event in people with a high risk of such events. Etezimibe reduces lipid levels by limiting the absorption of cholesterol in the intestine.

The authors of the updated also mentioned another new type of drug: pro-protein convertase subtilisin/kexin 9 (PCSK9) inhibitors. There is evidence that these drugs are effective at reducing cholesterol levels, especially when a person uses them with ezetimibe.

In 2018, new guidelines recommended a stepped approach, depending on how high an individual's risk is.

If a person has already had a cardiovascular event, such as a heart attack, a doctor may recommend using ezetimibe as well as a statin. For those at very high risk, the guidelines also recommend adding a PCSK9 inhibitor.

However, the guidelines also note that PCSK9 inhibitors are expensive, and insurance companies may not cover their cost. For this reason, this option is likely to be only for those with a very high risk.

Statin safety

The use of statins has caused some debate because, like all drugs, they can have side effects.

These include:

• statin-induced myopathy (a muscle tissue disease)
• fatigue
• a slightly greater risk of diabetes and diabetes complications, though this is hotly debated

A person should not stop taking a statin without speaking to a doctor, as they may increase their risk of cardiovascular problems.

A doctor might recommend:

• switching to a different medication
• increasing efforts to reduce cholesterol through lifestyle changes

Complications of high cholesterol

In the past, people have aimed to reduce cholesterol to a target level, for instance, below 100 mg/ dL, but this is no longer the case.

Randomized, controlled clinical trials have not produced enough evidence to support treatment to a specific target.

However, some physicians may still use targets to help guide therapy.

10-year risk of a heart attack

Cholesterol levels play a major part in an individual's risk of having a heart attack within the next 10 years.

The National Heart, Lung, and Blood Institute provide an online calculator of cardiovascular risk.

Using research evidence, it weighs the risk according to these factors:

• age
• gender
• cholesterol levels
• smoking status
• blood pressure

Guidelines published in 2018 consider this calculator and essential tool for assessing cholesterol levels and their risk.

Source: Medical News Today