What causes high cholesterol?

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 found in every cell of the body and has important natural functions when it comes to digesting foods, producing hormones, and generating vitamin D. It is manufactured by the body but can also be taken in from food. It is waxy and fat-like in appearance.
There are two types of cholesterol; LDL (low-density lipoproteins, bad cholesterol) and HDL (high-density lipoproteins, 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 is produced by the body but is also ingested from animal-derived foods.
• The greatest risk factors for high cholesterol are modifiable lifestyle choices - diet and exercise.
• Having high cholesterol does not usually produce any symptoms.
• If lifestyle changes are unsuccessful or cholesterol levels are very high, lipid-lowering drugs such as statins may be prescribed.

What is cholesterol?

High cholesterol has a number of causes, including dietary choices.

Cholesterol is an oil-based substance and does not mix with the blood, which is water-based. It is carried around the body by lipoproteins.
Two types of lipoprotein carry the parcels of cholesterol:

• Low-density lipoprotein (LDL) - cholesterol carried by this type is known as "bad" cholesterol.
• High-density lipoprotein (HDL) - cholesterol carried by this type 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 which plaques form and cause restriction of blood flow.
Reducing intake of fat in the diet helps manage cholesterol levels. In particular, it is helpful to limit foods that contain:

• Cholesterol - from animal foods, meat, and cheese.
• Saturated fat - found in some meats, dairy products, chocolate, baked goods, deep-fried, and processed foods.
• Trans fats - found in some fried and processed foods.

Being overweight or obese can also lead to higher blood LDL levels. Genetics can contribute to high cholesterol - very high LDL levels are found in the inherited condition familial hypercholesterolemia. Abnormal cholesterol levels can also arise due to other conditions, including:

• 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 (progestins, anabolic steroids, and corticosteroids)

High cholesterol symptoms

Having high cholesterol levels, while a risk factor for other conditions, does not itself present any signs or symptoms. Unless routinely screened through regular blood testing, high cholesterol levels will go unnoticed and could present a silent threat of heart attack or stroke.

Cholesterol in foods

Oily fish like salmon has been shown to actively decrease cholesterol.

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, including:

• 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 is considered a major risk factor for heart disease.
• A reading from 41 mg/dL to 59 mg/dL is borderline low.

Preventing high cholesterol

Four changes to lifestyle are recommended for all people with high cholesterol or who wish to ensure their levels remain normal. These changes will reduce the risk of coronary heart disease and heart attack:

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

How can high cholesterol be treated?

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

Lipid-lowering therapy

Drug treatment for an individual with hypercholesterolemia will depend on their cholesterol level and other risk factors. Diet and exercise are the first approaches used to reduce cholesterol levels. Statin treatment is normally prescribed for people with a higher risk of heart attack.
Statins are the leading group of cholesterol-lowering drugs; others include selective cholesterol absorption inhibitors, resins, fibrates, and niacin. 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)

Statin safety

The prescription of statins has caused considerable debate. While many patients benefit greatly from statin use to lower cholesterol and reduce their risk of heart attack, a significant number of patients also experience adverse effects from statins.
Side effects can include:

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

Switching to a different statin medication, or increasing efforts to reduce cholesterol through lifestyle changes may help relieve statin-induced myopathy and other unwanted effects of these drugs.

Complications of high cholesterol

In the past, people have aimed to reduce cholesterol to a target level, for instance, below 100 milligrams per decilitre; this is no longer the case. There is no evidence from randomized, controlled clinical trials 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
• sex
• cholesterol levels
• smoking status
• blood pressure