As more becomes known about cholesterol, lay people and doctors alike are concentrating more on the different types of cholesterol rather than the total cholesterol. Two important factors of the total cholesterol are high-density lipoprotein, sometimes called the "good" cholesterol, and low-density lipoprotein, often called the "bad" cholesterol. Several different types of ratios are used to determine cholesterol levels and predict heart disease risk.
Definition
Both LDL and HDL carry cholesterol particles through the bloodstream, because cholesterol is not water-soluble and can't travel through blood on its own. Low-density lipoproteins tend to be dense and hard; they stick to the walls of blood vessels, causing build-up known as plaque. High-density lipoprotein particles tend to be larger and fluffier; they pick up excess LDL particles and return them to the liver, lowering LDL cholesterol levels and decreasing atherosclerosis.
Methods
One ratio used to determine heart disease risk divides the LDL number into the HDL number, eMedTV explains. For example, if your HDL is 40 mg/dL and your LDL is 160 mg/dL, your ratio is 0.25. Another way to determine cholesterol ratio uses just the total cholesterol and HDL numbers. Divide your total cholesterol by your HDL, according to the Mayo Clinic. If you have a total cholesterol level of 150 mg/dL and an HDL of 50, your ratio is 3 to 1. Low-density lipoprotein levels are difficult to measure directly. They're normally determined by the following formula: total cholesterol -- HDL -- (Triglycerides ÷ 5) equals the LDL.
Uses
An HDL to LDL ratio above 0.3 is considered good, according to eMedTV, while a ratio of 0.4 or more is considered optimal. Using the Mayo Clinic method, a ratio of 4 to 1 or less indicates a decreased risk of heart disease while a higher ratio indicates a higher risk. The Harvard Family Health Guide states that, according to the Framington Heart Study, a ratio of 5 using the Mayo method for men indicates average risk, while a level of 3.4 or lower indicates about half the normal risk. A ratio of 9.6 doubles the average risk for men. For women, a ratio of 4.4 indicates normal risk, with a ratio of 3.3 halving the average risk and a ratio of 7 doubling the average risk.
Benefits
Keeping your total cholesterol level below 200 mg/dL is beneficial, but knowing your exact HDL and LDL levels gives more valuable information. An HDL level of 40 mg/dL indicates an increased risk of heart disease, while a level of 160 mg/dL protects your heart. Keeping LDL levels below 100 mg/dL gives optimal protection against heart disease, according to The Harvard Family Health Guide.
