Cholesterol Congestion
How your blood cholesterol traffic is measured
The odds of getting cardiovascular disease are very high; it is the main cause of death in the US and more than one in four Americans dies from this disease according to the CDC. “Measurement of your cholesterol levels will provide you and your doctor with the necessary data to assess your risk for cardiovascular disease” says Kim Birtcher, Clinical Associate Professor at the Department of Clinical Sciences and Administration, University of Houston. 1 You’ve probably heard that there is good and bad cholesterol, and your doctor will usually measure both. However, do we know which type of cholesterol is the best to predict your risk of heart disease? Cholesterol, why it’s good and can be bad
With the 155 billion dollar fast food industry 2 making Double Quarter Pounders with Cheese available at every street corner (filling you up with 19 grams of saturated fat, almost the maximum amount you are allowed to eat all day), it’s no surprise that one in six Americans have high cholesterol. 3 Cholesterol itself is not good or bad. “Cholesterol is a useful and even essential substance in our bodies.” says Martijn Katan, Professor of Nutrition at VU University, Amsterdam. You need cholesterol to build cell membranes, to make sex hormones and vitamin D, and without it you wouldn’t be able to eat fats at all: cholesterol is a part of bile, which helps digest and absorb fats and fat‐soluble vitamins in the intestine. However, too much of anything is usually a bad thing. From the Framingham Heart Study, a prospective cohort study among 5,209 man and women in Framingham Massachusetts dating back all the way to 1948, we have learned that high cholesterol is one of the factors that increase risk of heart disease. “You can best compare the total cholesterol in your bloodstream to traffic on the roads” says Martijn Katan, Professor of Nutrition at VU University, Amsterdam. “Too much traffic will lead to traffic jams and can cause your arteries to clog up with cholesterol and eventually result in a heart attack.” explains Katan.” Your total cholesterol is not the only measurement in a typical check‐up you get at the doctor’s office; LDL‐cholesterol, HDL‐cholesterol and triglycerides are also measured as part of a ‘lipid panel’ or ‘lipoprotein profile’, which we will explain more about later. There has been some discussion about which of these common measurements is the most accurate tool in telling you how high your risk of heart disease is. We’ve taken the time to find out for you what all these cholesterol measurements mean, and how they can help estimate your risk. Before we dive into the numbers, let’s go through the different types of cholesterol. Total cholesterol
Your ‘total cholesterol’ assesses all the cholesterol in your blood and is the easiest value to measure. “Since cholesterol is a waxy lipid that does not dissolve in blood plasma, it must be packaged and transported in blood within ‘packets’ of protein and lipid, called ‘lipoproteins’” says Frank Sacks, Professor of Cardiovascular Disease Prevention, Department of Nutrition at The numbers at a glance
Harvard School of Public Health. You might Total Cholesterol Level Category recognized some of these lipoproteins by the names of High Density Lipoprotein (HDL), Low Less than 200 mg/dL Desirable Density Lipoprotein (LDL) and Very Low 200 to 239 mg/dL Borderline high Density Lipoproteins (VLDL). Total cholesterol 240 mg/dL and above High blood cholesterol. A person with is the sum of all these cholesterol packages. Total cholesterol is measured as the sum of cholesterol carried in HDL, LDL, and VLDL. It’s a cheap test, and usually the first thing your doctor looks at. However, it measures both the good and the bad cholesterol, and that’s where the confusion starts. The good
About 20%‐30% of your cholesterol is transported in HDL, one of the protein packages that carries cholesterol through your blood. “HDL can best be compare to the traffic police and tow trucks, who make sure that traffic jams are solved, and cars with car trouble are removed” says Katan. “The more police and tow trucks on the streets, the better the traffic will flow, and the cleaner the streets.” That is why we call HDL‐cholesterol the ‘good’ cholesterol. this level has more than twice the risk of coronary heart disease as someone whose cholesterol is below 200 mg/dL.
HDL Cholesterol Level
Category Less than 40 mg/dL
(for men) Less than 50 mg/dL (for women) Low HDL cholesterol, at risk for heart disease. 6 0 mg/dL and above
High HDL cholesterol, protective of heart disease. LDL Cholesterol Level
Category Less than 100 mg/dL
Optimal 100 to 129 mg/dL
Near or above optimal
130 to 159 mg/dL
Borderline high 160 to 189 mg/dL
High 190 mg/dL and above
Very high National Cholesterol Education Program (NCEP) guidelines “HDL‐cholesterol in your blood directly counteracts the harmful effects of LDL‐cholesterol “ says Walter Willett, John Fredric Stare Professor at Harvard School of Public Health. Let’s see what harm this LDL‐cholesterol can do. The bad
LDL‐cholesterol makes up 60%‐70% of your blood cholesterol. “LDL‐
cholesterol can be compared to the cars that are clogging the streets.” explains Katan. Too much LDL‐cholesterol is a large independent risk factor for heart disease. That is because “cholesterol in LDL, reflects the cholesterol that is potentially going into the walls of the artery” says Sacks.4 LDL‐cholesterol is not measured directly. It is calculated from your total cholesterol, HDL cholesterol and triglyceride levels ‐‐ another marker in your blood that is related to heart disease. VLDL is the precursor for LDL, and contains much less cholesterol, about 10%–15% of the total cholesterol, but also contains some triglycerides ‐‐ the form in which fatty acids occur in your food, and these are also a risk factor for heart disease. Cholesterol out of proportion
All of these predictors of heart disease contain useful information about your health. However, some other estimates have been developed that combine individual cholesterol levels together, such as the total cholesterol to HDL‐cholesterol ratio, also called total:HDL‐cholesterol, the LDL:HDL‐
cholesterol ratio, or non‐HDL cholesterol. “These summarized values combine information contained in more than one cholesterol value.” Explains William Castelli, M.D. and researcher of the Framingham Heart Study. “From analyses in our study we have found that the ratios are useful expressions for combining cholesterol information and are strong predictors of coronary heart disease.” 5 Some evidence exists that these summary estimates of cholesterol predict the risk of heart disease better, than the individual values. The total:HDL‐cholesterol and LDL:HDL‐cholesterol ratios for example, are measures for the proportion of bad cholesterol in your blood, in one value. In a study among 3641 men in the Lipid Research Clinics Coronary Primary Prevention Trial the researchers found that “changes in total:HDL and LDL:HDL ratios were better predictors of risk for coronary heart disease than changes in LDL cholesterol levels alone” 6 Especially for people with high triglycerides, such as type 2 diabetics, the individual lipoproteins may not be such good predictors of heart disease. Because LDL‐cholesterol is measured indirectly trough triglycerides. High triglyceride levels might obscure your LDL‐cholesterol measurement. This has been confirmed in a study among 2099 diabetic participants of the Strong Heart Study, where “the ratios of total:HDL cholesterol, and LDL:HDL‐cholesterol had higher accuracy for predicting coronary heart disease than HDL and LDL cholesterol alone” says author of this paper Dongsheng Hu, MD, MPH at Washington Hospital Center, Washington, DC.7 Let’s ask the people from the National Cholesterol Education Program, who set the national recommendations for cholesterol testing and management. Their Expert Panel recommends that “in persons with high triglycerides (≥200 mg/dL), VLDL cholesterol should be combined with LDL cholesterol, yielding non‐HDL cholesterol.” Non‐HDL cholesterol is another handy tool to measure the absolute values (compared with the relative values in ratios) of all the bad cholesterol in LDL and VLDL. 8 But where to begin with this overload of cholesterol values. Are they any use for you as someone who just wants to know if their healthy? Your personal risk assessment
Measuring cholesterol alone does not give you the big picture. Your age, gender, smoking habits, blood pressure and use blood pressure reducing medicine also affect your personal risk. So when doctor tells you that your risk of getting heart disease is 1 in 10, then he is probably using the Framingham Risk Score. This score has been developed from data in the Framingham Heart Study and can calculate how large your risk is to get heart disease in the next 10 years. Your doctor puts these values in a formula to accurately estimate your risk of getting a heart attack or dying from heart disease in the next 10 years. 9 However, when you are 20 years old, your chances of getting a heart attack in the next 10 years are very low. That is why Dr. Michael Pencina from the Framingham Heart Study and his colleagues have estimated a 30‐year risk score. This new tool” Pencina says, “might increase the number of people who adopt a healthy lifestyle. When they hear that their risk is 1 in 8 for the next 30 years, instead of 1 in 50 in the next 10 years, they might take action to improve their health.” 10 Since you now know all there is to know about cholesterol values, you might want to know how you can beat the odds of getting heart disease. That’s what we’ll talk about next. How do foods affect
Resolving the cholesterol jam
It does not stop with estimating your heart disease risk. If you have high cholesterol levels, then you need effective treatment to reduce these levels. And that’s where these absolute values come in handy. Katan and colleagues evaluated the effects of individual fatty acids on measurements such as total:HDL cholesterol and other cholesterol levels. In a meta‐analysis of 60 controlled trials they found that “replacement of carbohydrates with any class of fatty acids decreased triglyceride levels”. That is a bad thing. This is one reason why measuring LDL‐cholesterol by itself will not be sufficient to see if the healthy dietary changes would have an effect. But the total:HDL‐cholesterol ratio might also not be the ideal measurement since “substitution of saturated fat for carbohydrate results in increases in HDL cholesterol, with no net effect on the total:HDL‐
cholesterol ratio” explains Katan. These are just some of the reasons, that we should not focus too much on one measurement alone. 11 According to Katan, the evidence for using the total: HDL‐cholesterol ratio is not complete: “The use of total:HDL cholesterol implies that diet‐induced cholesterol levels?
"The cholesterol in your food doesn't directly become cholesterol in your bloodstream. Rather, the fats in your foods stimulate your body to produce cholesterol. Different kinds of fat produce different kinds of cholesterol.” says Willett. “It’s the type of fat, not the total amount of fat, is what's important for having a good balance of the types of cholesterol in the blood”. Saturated fats, the type you can find in meats and full‐fat dairy products increase your LDL‐
cholesterol, so cut back on those. Even worse are trans fats, also called partially hydrogenated fats on the ingredient list. “ Trans fats raise bad LDL and lower good HDL‐
cholesterol” explains Willett. But don’t cut out all fats! "When people are told to get all the fat out of their diets and eat carbohydrates instead, they will lower their HDL and raise their triglycerides." Willett says. decreases in HDL cholesterol increase heart disease risk. Such a causal role for diet‐induced changes in HDL cholesterol has not been proven in controlled clinical trials” argues Katan. “However, results of prospective observational studies, controlled clinical trials with drugs, mechanistic studies, and genetic “experiments of nature” all strongly suggest that high concentrations of HDL cholesterol in the circulation help to prevent cardiovascular disease.” More studies should be done before we can use any of these combined values by itself. By measuring the effects of foods on cholesterol, we are still not sure whether they increase the risk of heart disease. Katan warns that “the favorable effects on the total:HDL‐cholesterol ratio by coconut fat do not exclude the possibility that coconut fat may promote heart disease through other pathways.” So don’t fill yourself up with coconut fat just yet. To know for sure, we have to do randomized controlled trials on the effects of foods on heart disease, which are very expensive, and almost impossible to conduct. 11 For epidemiological research on the effects of foods on cholesterol levels in large groups of people, these summary statistics might be very useful, and sometimes even better than the individual measurements. When you go check your cholesterol levels at your doctor’s office, however, the American Heart Association recommends using the absolute numbers for the different types of cholesterol. “For treatment purposes, it's more important to know absolute numbers for all your cholesterol levels — including HDL, LDL and total cholesterol — than to know ratios.” Says Thomas Behrenbeck, M.D., Ph.D and cardiologist at the Mayo Clinic. “This is because HDL cholesterol and LDL cholesterol both affect your heart disease risk, and treatment may be directed at improving both.” 12 The bottom line
According to the experts from the National Cholesterol Education Program report, all adults aged 20 years or older, should have their cholesterol checked every 5 years. This measurements should include total cholesterol, LDL‐cholesterol, HDL‐ cholesterol, and triglycerides.13 Knowing the absolute values is key: if either one of these values is high (or HDL is too low), your doctor will discuss ways to improve your levels and reduce your risk of heart disease. To lower your cholesterol and beat the odds of heart disease you can: ƒ
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cut back on saturated fat and dietary cholesterol, lose or avoid gaining weight, and exercise. That’s nothing new, we suppose. 1.
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Circulation. 2004; 110: e296‐e297. http://www.hoovers.com/industry/fast‐food‐quick‐service‐restaurants/1444‐1.html http://www.cdc.gov/cholesterol/facts.htm http://www.metabolicsyndromeinstitute.com/informations/experts‐opinion/Sacks_07.08/index.php Circulation. 1983;67:730‐734. J Investig Med. 1995 Oct;43(5):443‐50. Ann Epidemiol. 2002 Feb;12(2):79‐85. http://www.nhlbi.nih.gov/guidelines/cholesterol/atp3full.pdf Circulation. 1998;97:1837‐1847. 10.
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Circulation.2009; 119: 3078‐3084. Am J Clin Nutr 2003;77:1146–55. http://www.heart.org/HEARTORG/Conditions/What‐Your‐Cholesterol‐Levels‐Mean_UCM_305562_Article.jsp http://www.nhlbi.nih.gov/guidelines/cholesterol/atp3full.pdf