Dietary Cholesterol

Cholesterol is a soft, white, waxy substance found in the lipids of the bloodstream and in the cells of the body. There are two sources of cholesterol. The first is the body, mainly the liver, which produces typically about one gram per day. The second are cholesterol-containing foods from animal sources, especially egg yolks, meat, poultry, fish, seafood, and whole-milk dairy products. Cholesterol in foods is called dietary cholesterol.

Cholesterol is found in every cell of the body. It has several important functions in maintaining health, such as:

Dietary cholesterol

However, excess cholesterol has been shown to accumulate in the bloodstream and on the walls of arteries, forming “plaques” that can clog the blood vessels (atherosclerosis) and lead to heart attack or stroke. Because high blood cholesterol is one of the major risk factors for heart disease, dietary cholesterol has been the focus of much debate over what constitute healthy or unhealthy levels of cholesterol in the blood and how to lower cholesterol in the diet.

Dietary cholesterol is found in animal food sources such as meat, poultry, seafood, and dairy products. Foods from plants, such as fruits, vegetables, vegetable oils, grains, cereals, and nuts and seeds do not contain cholesterol. Major sources of dietary cholesterol include meats and poultry (beef, chicken, pork, lamb), seafood (squid, salmon, tuna), and dairy products (eggs, ice cream, cheese, milk, butter).

Cholesterol does not dissolve in blood. It has to be transported to and from the cells by special carriers called lipoproteins, which are present in blood plasma. The most important forms of lipoproteins are:

Generally speaking, LDL levels should be low because LDL deposits cholesterol in the arteries and causes them to become clogged. HDL levels should be high because HDL helps clean fat and cholesterol from arteries, carrying it to the liver for removal from the body. This is why HDL is often called the “good cholesterol” and LDL the “bad cholesterol,” although studies conducted in 2012 began to challenge this belief.

The American Heart Association (AHA) endorses the following dietary recommendations for people with high blood cholesterol:

Categories of appropriate foods include:

Making smart dietary choices can prevent cholesterol levels from being too high. Some fats, such as mono- and polyunsaturated fats, may lower LDL cholesterol levels. Other fats, such as saturated and trans fats, raise cholesterol. Sources of fats include:

Other suggested guidelines include:

Some foods may actually lower a person's cholesterol. Soluble fiber has been shown to help reduce LDL cholesterol levels when eaten as part of a healthy diet. Specific cholesterol-lowering foods include:

Plant sterols and stanols, found in trace amounts in plant-based foods, have been found to reduce LDL cholesterol levels by up to 15%. Because the amounts obtained through dietary sources are low, foods fortified with plant sterols are available.

The National Heart, Lung, and Blood Institute (NHLBI), through its National Cholesterol Education Program (NCEP), recommends that adults begin cholesterol screening at age 20 and repeat the screening every five years. People who have one or more risk factors for developing heart disease (for example: diabetes, kidney disease, high blood pressure, vascular disease, or a history of elevated cholesterol levels) should have their cholesterol levels checked more often.

Simple blood tests are done to check blood cholesterol levels. A lipoprotein test, also called a fasting lipid test, is commonly performed as part of a routine medical examination. A cholesterol test measures lipid levels and usually reports on four groups:

If dietary cholesterol intake is excessive, it can lead to an elevation of lipid levels in the bloodstream, a condition known as hyperlipidemia. These lipids include cholesterol, phospholipids, and triglycerides (fats). Hypercholesterolemia is the term for high cholesterol levels, and hypertriglyceridemia is the term for high triglyceride levels. Because cholesterol-rich foods are also usually high in saturated fat, hypercholesterolemia is often combined with hypertriglyceridemia. Hyperlipidemias have been shown to represent a major risk factor for heart disease, a leading cause of death in the United States.

See also Fats; Hyperlipidemia; Hypertriglyceridemia; Low-cholesterol diet; Omega-3 and omega-6 fatty acids; TLC diet; Trans fats; Triglycerides.

Monique Laberge, PhD