As infamous as cholesterol may be, your body cannot do without it. It is an indispensable component of all cell membranes that also forms the backbone of bile acids, steroid hormones and vitamin D. However, not all cholesterol is desirable. Indeed, excessive levels of LDL, or "bad cholesterol," have been associated with heart disease risk. LDL levels are usually tested as part of a broader cholesterol profile, or lipid panel.
Function
LDL stands for low-density lipoprotein. Lipoproteins are special carrier molecules that bind to cholesterol in order to enable it to transit through your bloodstream. LDL is the most abundant of lipoproteins, accounting for 60 to 70 percent of your total blood cholesterol, according to the Harvard Medical School. It carries cholesterol from your liver to various organs throughout your body.
Features
According to England's University of Surrey biochemist Jack Salway, lipoproteins consist of different proportions of proteins, cholesterol, modified cholesterol known as cholesteryl esters, and other fats. For instance, Salway notes that LDL contains approximately 45 percent of cholesterol and only 20 percent of protein. In contrast, HDL, or high-density lipoprotein, contains about 18 percent of cholesterol and 50 percent of proteins and is known as "good" cholesterol. Lipoproteins that contain mostly protein are considered beneficial.
Significance
If your blood becomes overloaded with LDL particles, cholesterol may begin sticking to your blood vessel walls, forming fatty deposits known as plaque. Plaque formation, or atherosclerosis can narrow blood vessel openings to the point of obstructing the flow of blood and oxygen, explains Salway. Interrupted blood flow to the heart or brain can lead to a heart attack or a stroke, respectively. HDL is particularly important because it removes excess cholesterol from your bloodstream and carries it to the liver for disposal.
Blood Levels
The American Heart Association, or AHA, considers LDL levels below 100 mg/dL to be most desirable. However, if your levels fall between 100 and 129 mg/dL, you're still within the norm. Borderline high LDL cholesterol is defined by levels ranging from 130 to 159 mg/dL. At 160 mg/dL and beyond, your levels would be considered high.
Risk Factors
Keeping your LDL count below 100 mg/dL becomes especially important if you already have coronary heart disease, notes the AHA. For those with two or more risk factors, a goal of less than 130 mg/dL is desirable, while those with one or no risk factor can aim for LDL counts below 160 mg/dL. Examples of risk factors include: smoking, lack of physical activity, obesity, diabetes, a family history of heart disease, high blood pressure, and being a man over the age of 45 or a woman over the age of 55.
Prevention/Solution
To help you reduce your LDL levels, the Mayo Clinic recommends such measures as losing excess weight, quitting smoking, engaging in regular physical activity and adopting a diet that is low in fat but rich in fruits, vegetables, whole grains, nuts and omega-3 fatty acids. A good rule of thumb is for fats to represent about 25 to 35 percent of your daily calories, according to the Cleveland Clinic. However, you should limit your intake of saturated fats to no more than 10 percent of your total calories, and avoid all trans fats. Red meats and dairy products are rich in saturated fats, while hydrogenated oils contain trans fats. Monounsaturated fats, found in such vegetable oils as olive oil, are considered healthier.
References
- "Medical Biochemistry at a Glance"; Jack G. Salway, Ph.D.; 2006
- Harvard Medical School: Making Sense of Cholesterol Tests
- American Heart Association: Cholesterol Levels
- Mayo Clinic: High Cholesterol
- Cleveland Clinic: Nutrition Guidelines
