Do you have any information on cholesterol?

Dear Seeking fat,

Cholesterol is a white, waxy lipid (fat) found naturally in the human body. Most cholesterol is produced by the liver, while a smaller amount is ingested directly from meat, poultry, seafood, dairy products, and other foods of animal origin (plant foods do not contain cholesterol). Cholesterol is involved in many vital life-processes, such as the production of hormones and the repair of cell membranes. To get where it's needed, cholesterol travels through the bloodstream as lipoproteins — fat packaged up in little protein spheres.

Studies have demonstrated that a blood test measuring cholesterol levels can help establish one's risk for heart disease. This test measures the amount of fat found in the bloodstream, including high-density lipoproteins (HDL), low-density lipoproteins (LDL), and triglycerides (another type of fat molecule). A total cholesterol score is then obtained by putting these three numbers into a mathematical formula. Research has shown that high levels of HDL decrease one's risk for heart disease (hence the term "good" cholesterol), while high LDL levels (a.k.a. "bad" cholesterol) increase one's risk. The medical community currently uses the following guidelines to put these numbers in perspective:

• Total cholesterol: less than 200 milligrams (mg)/deciliter (dL)
• LDL: less than 130 mg/dL
• HDL: more than 60 mg/dL
• Triglycerides: less than 150 mg/dL

Because the total cholesterol score is a composite that includes both "good" and "bad" cholesterol, this number alone is less useful as an indicator of risk than the ratio of total cholesterol to HDL. For example, having a total cholesterol number above 200 mg/dL indicates a statistically greater risk of heart disease, but if this number is arrived at because the HDL number is especially high while the LDL and triglyceride numbers are normal or low, then the risk level may actually be below average. The ideal total cholesterol to HDL ratio is less than 3.5; a ratio of 4.5 is average, while a ratio of 5 or greater is a red flag.

Blood cholesterol levels vary according to genetics as well as lifestyle choices. For example, eating saturated fats is the largest contributor to high blood cholesterol levels. Other lifestyle factors include smoking, which is associated with lowering HDL levels (increasing risk), and regular exercise, which is associated with boosting them (lowering risk).

For more detailed information on cholesterol, read the related Q&As or visit the American Heart Association web site.