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:
- keeping cell membranes intact
- boosting mental performance
- helping digestion
- building strong bones
- building muscle
- maintaining energy, vitality, and fertility
- regulating blood sugar levels
- repairing damaged tissue
- protecting against infectious diseases
Beef liver, cooked, 3 oz.
Beef sweetbreads, cooked, 3 oz.
Squid, cooked, 3 oz.
Egg, whole, large
Shrimp, cooked, 3 oz.
Ice cream, gourmet, 1 cup
Salmon, baked, 3.5 oz.
Lamb chop, cooked, 3 oz.
Chicken breast, cooked, 3 oz.
Beef, round, cooked, 3 oz.
Beef, sirloin, cooked, 3 oz.
Pork chop, cooked, 3 oz.
Chicken, dark meat, cooked, 3 oz.
Beef, rib eye, cooked, 3 oz.
Ham, regular, cooked, 3 oz.
Tuna, water packed, drained, 3.5 oz.
Milk, whole, 1 cup
Butter, 1 tbsp.
Ice cream, light, 1 cup
Cheese, cheddar, 1 oz.
Scallops, cooked, 3 oz.
Hot dog, beef, 1 frank
Cheese, reduced fat, 1 oz.
Yogurt, part skim, 1 cup
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:
- Very high-density lipoprotein (VHDL). VHDL consists of proteins and a high concentration of free fatty acids.Page 348 | Top of Article
- High-density lipoprotein (HDL). HDL helps remove fat from the body by binding with it in the bloodstream and carrying it back to the liver for excretion in the bile and disposal. High levels of HDL may lower chances of developing heart disease or stroke.
- Intermediate-density lipoprotein (IDL). IDLs are formed during the degradation of very-low-density lipoproteins; some are cleared rapidly into the liver and some are broken down to low-density lipoproteins.
- Low-density lipoproteins (LDL). LDL transports cholesterol from the liver and small intestine to tissues outside the liver (extrahepatic) and other parts of the body. High LDL levels may increase chances of developing heart disease.
- Very low-density lipoprotein (VLDL). VLDLs carry triglycerides from the intestine and liver to fatty (adipose) and muscle tissues. A high VLDL level can cause a buildup of cholesterol in the arteries and increase the risk of heart disease and stroke.
- Chylomicrons. Chylomicrons are proteins that transport cholesterol and triglycerides from the small intestine to tissues after meals.
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:
- total fat: 25% of total calories
- saturated fat: less than 7% of total calories
- polyunsaturated fat: up to 10% of total calories
- monounsaturated fat: up to 20% of total calories
- carbohydrates: 50%–60% of total calories
- protein: about 15% of total calories
- cholesterol: less than 200 mg/dL
- plant sterols: 2 g
- soluble fiber such as psyllium: 10–25 g
Categories of appropriate foods include:
- lean meat or fish: less than 5 oz/day
- eggs: less than two yolks per week (whites unlimited)
- low-fat dairy products (1% fat): 2–3 servings/day
- grains, especially whole grains: 6–8 tsp/day
- vegetables: less than 6 servings per day
- fruits: 2–5 servings per day
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:
- monounsaturated fats (lower LDL, raise HDL): olives, olive oil, canola oil, nuts, avocados
- polyunsaturated fats (lower LDL, raise HDL): corn, soybeans, safflowers, cottonseed oils, fish
- saturated fats (raise both LDL and HDL): whole milk, butter, cheese, ice cream, red meat, chocolate, coconuts
- trans fats (raise LDL): most margarines, vegetable shortening, partially hydrogenated vegetable oil, deep-fried chips, many fast foods, most commercial baked goods
Other suggested guidelines include:
- Select lean meats and poultry. Choose chicken and turkey without skin or remove skin before eating. Dry peas, beans, and tofu are low in saturated fat and cholesterol and can be eaten as alternatives to meat.
- Egg yolks are high in dietary cholesterol (213 mg per yolk). They should be limited to no more than two per week, including the egg yolks in baked goods and processed foods. Egg whites have no cholesterol and can be substituted for whole eggs when baking.
- Choose low- or reduced-fat dairy products (milk, cheese, yogurt, ice cream) over those made with whole milk.Page 349 | Top of Article
- Limit butter, lard, and solid shortenings.
- Eat lots of fruits and vegetables, which are low in fat and high in fiber.
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:
- fish high in omega-3 fatty acids, such as salmon
- olive oil
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:
- total cholesterol (normal: 100–199 mg/dL)
- LDL (normal: less than 100 mg/dL)
- HDL (normal: 40–59 mg/dL)
- triglycerides (normal: less than 150 mg/dL)
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.
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Centers for Disease Control and Prevention, Division for Heart Disease and Stroke Prevention, 4770 Buford Hwy NE, Mail Stop F-72, Atlanta, GA, 30341-3717, (800) CDC-INFO (232-4636), TTY: (800) 232-6348, Fax: (770) 488-8151, email@example.com, http://www.cdc.gov/dhdsp .
National Heart, Lung, and Blood Institute, PO Box 30105, Bethesda, MD, 20824-0105, (301) 592-8573, TTY: (240) 629-3255, Fax: (240) 629-3246, firstname.lastname@example.org, http://www.nhlbi.nih.gov .
Monique Laberge, PhD
Gale Document Number: GALE|CX2491000093