Most people know that high cholesterol puts them at risk for heart disease and other illnesses, and that keeping cholesterol levels low is important for their overall health. However, many don't fully understand what cholesterol is, the important role it plays in the body or what a low cholesterol level really means.
Cholesterol Definition
The Yale School of Medicine explains that cholesterol is a waxy, fatty substance, called a lipid, that your body requires for a number of functions. Your liver produces most of your body's cholesterol, and the rest is brought in through the foods you eat. Your blood carries cholesterol around your body, depositing it where it's needed. Because fatty substances don't blend well with your water-based blood, cholesterol requires a special protein casing, called a lipoprotein, to help it move freely through your bloodstream. Cholesterol is a component of your cell membranes. It also helps form testosterone and estrogen hormones, and helps the liver produce bile, a substance that breaks down fats.
Cholesterol Function
When there is too much cholesterol in your bloodstream, it begins to form deposits in in your blood vessels. These deposits, called plaque, can build up and harden over time, blocking normal blood flow. Pieces can break off and clog main arteries, causing embolisms or strokes. If too much cholesterol builds up in the walls of your heart's arteries, you may be at risk for heart disease and heart attacks.
Cholesterol Types
The two main types of cholesterol are high-density lipoprotein, or HDL cholesterol, and low-density lipoprotein, or LDL cholesterol. HDL cholesterol has a a high protein-to-fat ratio, and LDL cholesterol has a low fat-to-protein ratio. While HDL takes cholesterol from the blood and carries it to the liver for excretion, LDL takes cholesterol from the liver and deposits it in blood vessels. For these reasons, LDL is considered "bad" cholesterol, and HDL is considered "good" cholesterol.
Guidelines
Blood cholesterol levels are measured in milligrams per decaliter, or mg/dL. According to the American Heart Association, your total cholesterol level should ideally be lower than 200 mg/dL. A level of 200 to 239 mg/ dL is considered moderately high, and a level of 240 mg/dL is considered very high.
Your LDL and HDL cholesterol levels are a better indicator of heart disease risk than your total cholesterol levels. Ideally, your LDL level should be less than 100 mg/dL. 160 to 189 mg/dL is considered high, and 190 mg/dL and above is considered very high. With HDL cholesterol, higher levels are better than lower levels. Optimum HDL levels are 60 mg/dL and above. Men with HDL levels lower than 40 mg/dL and women with levels lower than than 50 mg/dL are at high risk for developing heart disease.
Considerations
Guidelines for optimum cholesterol levels are somewhat general. Your doctor will make recommendations based on your specific needs. People already at a high risk for heart disease, such as those who are obese or smoke, or those who have a family history of heart disease, will have stricter cholesterol guidelines than those at a lower risk. The best way to improve your cholesterol levels is to eat a balanced diet and exercise regularly.
