If you're like most people, your conception of cholesterol probably vacillates that of a "friend" or a "foe." Fact is it can be both. Cholesterol does have an important role in the body, including cell membrane composition and the production of steroid hormones, bile acids and vitamin D. However, excess cholesterol can increase heart attack and stroke risk, notes the American Heart Association (AHA). This is particularly true regarding high LDL (low-density lipoprotein), or "bad" cholesterol, hence the importance of knowing both your LDL count and cholesterol ratios.
Basics
As a highly hydrophobic, or water-hating, substance, cholesterol must transit through your blood attached to transport molecules known as lipoproteins. Although the proportions differ, all lipoproteins are comprised of cholesterol, protein, phospholipids and triacylglycerols. Examples include high-density lipoprotein, or HDL, very low-density lipoprotein, or VLDL, and LDL. Cholesterol represents approximately 45 percent of the LDL structure, notes University of Surrey biochemist Jack Salway. This is two to three times the average cholesterol content in HDL and VLDL. Thus, high total blood cholesterol is often associated with a high LDL count.
Significance
LDL carries cholesterol from the liver to your various organs. Conversely, HDL transports cholesterol from the bloodstream to your liver for elimination. The dangers of excess LDL lies in the fact that it tends to accumulate on the walls of your arteries, forming fatty deposits known as plaque. This plaque may grow enough to limit or block the flow of blood to your heart, according to Salway. Disrupted blood flow to the brain can result in a stroke, while blocked flow to the heart precipitates heart attack.
LDL Levels
The lower your LDL numbers, the better. Although good health and the absence of heart disease risk factors may give you some leeway, the AHA considers LDL levels below 100 mg/dL optimal for adults. The norm, however, would be for your LDL number to fall between 100 and 129 mg/dL. Levels ranging from 130 to 159 mg/dL are considered borderline high, while a LDL count exceeding 160 mg/dL is high.
Other Cholesterol Values
Your HDL level and total cholesterol count are also important for the calculation of cholesterol ratios. Ideally, you should have a total cholesterol count below 200 mg/dL. Levels ranging from 200 to 239 mg/dL would put you in the "borderline high" category, according to the AHA guidelines. Compared with an individual whose cholesterol is lower than 200 mg/dL, a total count of 240 mg/dL and above more than doubles your risk of developing heart disease. Regarding HDL, normal levels exceed 40 mg/dL for men and 50 mg/dL for women. However, you need a minimum count of 60 mg/dL in order to experience HDL's heart-protective effects, notes the AHA.
Total Cholesterol/HDL Ratio
In the absence of further specification, the phrase "cholesterol ratio" usually refers to your total cholesterol/HDL ratio. You can calculate it by dividing your HDL count into your total cholesterol count. For instance, if you have a total cholesterol value of 180 mg/dL and your HDL count is 60 mg/dL, your cholesterol ratio is 3:1. According to the AHA, you should aim for a total cholesterol/HDL ratio of 5:1 or lower. However, a ratio of 3.5:1 or lower is more favorable.
Good Versus Bad Cholesterol
Another useful, although less commonly calculated ratio, is your LDL-to-HDL value. You can simply calculate it by dividing your HDL count into your LDL count. Your goal, according to eMedTV, should be a LDL/HDL ratio that is lower than 3.5:1, with the optimum being under 2.5:1. A reciprocal ratio is your HDL-to-LDL value, which also compares good and bad cholesterol. You can obtain it by dividing LDL into HDL. Ideally, your HDL-to-LDL count should be higher than 4:1, although eMedTV deems it acceptable as long it is above 3:1.
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Considerations
Although cholesterol ratios give you an idea of your heart disease risk, doctors usually consider your absolute cholesterol numbers more useful for treatment or prevention purposes. To better guide your decisions, health care providers must look at your numbers in the light of other risk factors, including: obesity, age, gender, a family history of heart disease, cigarette smoking, high blood pressure and physical inactivity.
References
- ''Medical Biochemistry at a Glance;" J.G. Salway, PhD; 2006
- American Heart Association: Cholesterol Levels
- American Heart Association: Cholesterol Ratio
- eMedTV: Cholesterol Ratio
