Low-Density Lipoprotein

Low-density lipoprotein (LDL) is cholesterol packaged in a protein and phospholipid coat. Cholesterol is insoluble, so it must be encased in this coat to facilitate transport in the blood. LDL is the major cholesterol carrier in the blood. It circulates throughout the body and is available to all cells.

Cholesterol is a waxy substance found in the cell membranes of all animal tissues. It is actually a steroid and not a fat. Cholesterol aids in the production of bile in the liver as well as being a component in the production of hormones including estrogen and testosterone. The body is designed to make adequate cholesterol, called endogenously produced cholesterol. However, additional cholesterol may come from dietary sources, including eggs, milk, cheese, butter, meat, fish, and poultry. Cholesterol is not found in plants, so high-fat vegetables and fruits like avocado and nuts do not have cholesterol.

As LDL circulates in the blood, it may adhere to arterial walls which feed the heart and brain. It forms plaque and may result in a blockage in the artery which may lead to atherosclerosis. A blockage in coronary arteries may result in a heart attack while a blockage in the carotid may result in a stroke.

Diets high in saturated fat, trans-fat, and cholesterol increase LDL. Saturated fats are primarily from animal sources of foods. Coconut oil, palm oil, and palm kernel oil are also saturated fats. Trans-fats are fats that have been hardened through hydrogenation, a process in which hydrogen atoms are forced onto the chains of carbon that make up fatty acids. They include stick margarine, shortening, commercial frying oil, and high-fat baked goods. Not all dietary cholesterol becomes blood cholesterol. It is the amount of total fat intake, especially saturated fats and trans-fat which may influence cholesterol levels.

Overweight and obese individuals tend to have increased LDL. Lifestyle and genetic factors are the primary contributors to elevated LDL. Lifestyle factors include smoking, overeating, and inadequate physical activity. Blood cholesterol may rise after the age of 20. Gender may play a role as menopause in women decreases estrogen production which aids in keeping LDL low.

It is recommended that total blood cholesterol be less then 200 milligrams per deciliter (mg/dl). LDL should be lower than 130mg/dl. An LDL lower than 100mg/dl is recommended if coronary heart disease (CHD) has been diagnosed. There are no symptoms presented with high cholesterol; therefore, a fasting blood test of serum cholesterol to determine the total lipid profile will provide information on HDL, LDL, and triglycerides.

Treatment for high LDL usually begins with lifestyle changes by increasing activity, making dietary changes, and losing excess weight. A drug classified as a statin may be prescribed by a physician to lower LDL. A statin works by blocking an enzyme used in cholesterol production. Lifestyle adjustments in conjunction with statins may lower LDL if lifestyle changes alone do not work or if there is a family history of high cholesterol.