Cholesterol: When It's Good, It's Very, Very
It is the cholesterol-carrying protein in your blood that acts like arterial Drano, helping to keep critical blood vessels from clogging up with circulation-impeding deposits.
In true carnivores like lions, black bears and even dogs the good cholesterol runs very high, protecting them from coronary artery disease and stroke that might otherwise afflict heavy meat eaters. But people aren't carnivores; we're omnivores, and our anatomy more closely resembles herbivores like cows and deer, strict vegetarians, consuming only plant-based foods.
While you and your doctor may be more concerned with your total cholesterol or the amount of L.D.L.-C. (low-density lipoprotein cholesterol, the bad cholesterol) or triglycerides in your blood, actually a low level of good cholesterol is the most common lipoprotein abnormality in people with cardiovascular disease.
Further, said Dr. Michael Miller, who directs the Center for Preventive Cardiology at the University of Maryland Medical Center, low levels of good cholesterol best predict the risk of having a heart attack, even if total cholesterol is normal.
High-density lipoprotein transfers cholesterol from various parts of the body to the liver, where it is excreted. The low-density type, on the other hand, is the source of cholesterol that narrows the artery walls.
Most people, women as well as men, who suffer heart attacks have H.D.L. readings below 40 milligrams per deciliter of blood serum. In the latest version of the National Cholesterol Education Program's treatment guidelines, a reading below 40 is ranked as an independent risk factor in heart disease.
In fact, as Dr. Miller recently noted in The Cleveland Clinic Journal of Medicine, "Several studies have shown coronary heart disease risk to be more strongly or consistently related to H.D.L.-C. levels than to L.D.L.-C. levels."
The high-density lipoprotein level influences coronary risk no matter how high or low the low-density lipoprotein level may be, he added. An increase of 1 percent in the high-density type has been linked to a reduction of 2 to 3 percent in the incidence of heart attacks.
Vegetarians tend to have low levels of good cholesterol, Dr. Miller said. But for anyone who consumes animal-based foods that contain cholesterol or saturated fat, the higher the good cholesterol, the better.
"How high should H.D.L. be?" I asked him.
"As high as you can get it," he replied, adding that for men the goal should be above 45 milligrams and for women above 55 milligrams. The larger the proportion of good cholesterol to your total cholesterol level, the lower your coronary risk.
Doing the Math
The average ratio of total cholesterol to good cholesterol is 4.5 to 1 in the United States, and among those with established heart disease it is 5.5 to 1, Dr. Miller said. But in the Framingham Heart Study, those who were least likely to suffer heart attacks had ratios of 3 to 1 or better.
Let's say your total cholesterol level is 210 milligrams per deciliter of blood serum. To achieve a ratio of 3 to 1, you'd need an H.D.L. of 70. But if your total cholesterol is 150, a reading of 50 in good cholesterol will suffice, and if the total is 120, a good cholesterol level of 40 is the goal.
Strategies for raising levels of good cholesterol include medications and changes in diet and habits. Let's start with weight. Overweight or obese people are more likely to have abnormal levels of blood lipids, including low levels of good cholesterol and elevated triglyceride levels. Weight loss raises the high-density lipoprotein levels but not necessarily during dieting. But once the weight is lost, Dr. Miller wrote, "there is a surge in the H.D.L.-C. level of about one milligram per deciliter for every seven pounds lost."
While there is no magic for selectively raising the good cholesterol, certain diets favor a higher level. Interestingly, one of them is not low-fat. If you merely reduce dietary fat and replace it with carbohydrates without also reducing the number of calories consumed, levels of good cholesterol may fall as much as 20 percent, Dr. Miller noted.
But the kind of fats consumed can make a difference. Evidence indicates that foods rich in monounsaturated fats like canola and olive oil, most nuts and avocados can improve levels of good cholesterol without raising the total. Polyunsaturates like corn, safflower and soybean oils tend to lower the levels of both the good and the bad.
The idea, then, is to replace harmful saturated fats and refined carbohydrates (sugars and white starches) with monounsaturates without increasing total calories. Dr. Miller cautioned that by increasing carbohydrate consumption above 60 percent of calories, triglyceride levels rise, even if all the carbohydrates are whole grains.
Dr. Miller favors a Mediterranean-style diet with 30 to 35 percent of calories coming from fat. It consists of lots of vegetables and fruits, nuts and fish but little meat or high-fat dairy products. The best fish are the fatty ones, rich in omega-3 fatty acids, like Atlantic salmon and mackerel.
A Wholesome Approach
Accompanying this wholesome diet can be a moderate amount of alcohol, linked in about three dozen large studies to protection against heart disease. One to two ounces of alcohol a day can raise the good cholesterol level by 5 to 10 percent. Moderate alcohol consumption further protects the heart by diminishing the tendency of the blood to form clots and improving the functioning of blood vessel linings.
Even more important than diet to raising good cholesterol, however, is regular aerobic exercise, and the benefit, Dr. Miller says, is "dose-related." In other words, the more aerobic exercise one does, the higher good cholesterol is likely to be. Those who are not star athletes will be pleased to know that duration, not intensity, is most beneficial.
But to glean a significant benefit, studies suggest that you have to expend at least 1,200 calories a week on aerobic activities like running, brisk walking or lap-swimming. On average, a mile run or brisk walk uses about 100 calories. Good cholesterol rises about a milligram for every four or five miles covered each week.
Drugs can help, too, if diet and exercise are not enough. B vitamin niacin has the most potent effect on good cholesterol, Dr. Miller said, raising it as much as 30 percent. It is best taken with food and in extended-release preparations.
Statins, now the most popular heart-protective drugs, have a modest effect on good cholesterol, raising it by about 5 to 10 percent. The fibrates gemfibrozil (Lopid) and fenofibrate (Tricor) can raise good cholesterol 5 to 20 percent.
The bile-acid resins cholestyramine (Questran), colestipol (Colestid) and colesevelam (Welchol) and beta-agonists like terbutaline also help to raise good cholesterol by 5 to 10 percent. Although estrogen provides an even bigger benefit, 10 to 20 percent, it is no longer recommended for preventing heart disease in women.