Cholesterol levels are being tested all over the world in order to determine risk factors for heart disease, yet many people are confused by their cholesterol numbers and how they are expressed. Part of this confusion may stem from the fact that literature originating in the United States gives cholesterol levels in units that are different from those used in Canada, Europe, and a good portion of the rest of the developed world. So when you are looking for information to help you understand your test results, on the internet and elsewhere, you might not understand the numbers that are reported in the American literature because they might look quite different from the cholesterol numbers on your lab report.
The United States reports cholesterol levels in mg/dL (milligrams per decilitre) of blood. The rest of the world is using the measurement called mmol (or millimoles per litre). Without going back to basic chemistry from high school, let’s just say that they are different measurements. So is it any wonder that these two ways of expressing your cholesterol numbers are so different?
Here is how the two different systems of measurement stack up for desirable cholesterol numbers.
As expressed in the system of measurement used in the United States
Total cholesterol = less than 200 mg/dL LDL = less than 100-129 mg/dL (below 100 is best) HDL = more than 40 mg/dL (greater than 60 is considered protective against heart disease)
However, as expressed in the SI units (International System of Measurement) that most of the world is using the numbers are stated differently. (You can remember which letters refer to the good and the bad stuff by remembering it this way…H stands for healthy and L stands for lousy.)
Total cholesterol = less than 5.2 mmol/L LDL = in the range of than 2.6 – 3.3 mmol/L (less than 2.6 is best) HDL = in the range of more than 1 to 1.5 mmol/L (higher is better) mmol/L
Can you see the difference in how the cholesterol numbers are expressed? The difference of course is in the units that are being measured. Think of it like metric and imperial measures. Your weight in pounds might be a three digit number but in kilograms it could be a two digit number. Same weight different measurements.
Understanding the Cholesterol Ratio
When used to determine if you have cholesterol risk factors for heart disease it is not the specific levels that are analyzed but rather the ratio of HDL in your total lipid profile. This number is called the cholesterol ratio and it gives an indication of how much of your total cholesterol is the “good” stuff.
The reason this is important is because the HDL is so beneficial, if it is present is sufficient quantities it has a protective effect and the LDL in your system cannot do as much damage. So even if your LDL is higher than the desired levels, if the HDL is high as well and the ratio comes within the desired range then the risk of heart disease is less.
The goal is to keep the cholesterol ratio below 5:1; the optimum ratio is 3.5. The cholesterol ratio comes in at the same number no matter which system of measurement is used. The cholesterol ratio is obtained by dividing the total cholesterol number by the value given for the HDL. For example, if a you have a total cholesterol of 240 mg/dL and an HDL of 60 mg/dL, the ratio is 4. Using the SI system of measurement if the total cholesterol is 7.20 mmol/L and the HDL is 1.8 mmol/L the ratio is still 4.
You can see how this is a better way of understanding the cholesterol risk factors for heart disease and expressing it this way can prevent confusion that might result from not being familiar with the units that are used. This information is also helpful for understanding why the strategies recommended for cholesterol imbalances work. Some of the best strategies are the ones that raise the HDL levels. In particular, exercise has been found to be one of the best ways to improve the cholesterol ratio because it raises HDL levels. By contrast smoking has been found to lower HDL levels so no exercise and smoking is a recipe for low HDL levels, a poor cholesterol ratio, and a higher risk for heart disease.
Cholesterol is found in every cell of the body and is essential for the maintenance of good health. Low cholesterol levels have been associated with poor health so the goal is not to eliminate or reduce cholesterol entirely but to obtain the desirable levels of each type so that the protective benefits of the HDL can work for you in maintaining good health.
So don’t get mixed up when trying to understand your cholesterol levels. No matter what way the numbers are expressed the message is the same. You want to have enough of the good stuff and not so much of the bad stuff in order to reduce your risk factors for heart disease.