As knowledge has grown, the goals of treatment have changed, with
lifesaving effects. And now they are changing again.Over the last 40 years, heart specialists have learned a lot about the way cholesterol behaves in the body, much to the benefit of Americans destined to suffer heart attacks or strokes - at least half of the population.
As knowledge has grown, the goals of treatment have changed, with
lifesaving effects. And now they are changing again.
At first, pioneers bent on preventing cardiovascular disease focused only on a person's total blood cholesterol level. A level of 240 milligrams per deciliter of blood serum was considered "normal" just a few decades ago. Then research, like the Framingham Heart Study in Massachusetts, showed that at least half of heart attack victims had cholesterol levels of 240 or below.
Today, the goal for total cholesterol is 200 or less, preferably 180 if you want to remain heart-healthy. Cholesterol is not soluble in water and thus requires substances called lipoproteins to carry it in blood.
As the chemistry and physiology of cholesterol became better understood through the work of scientists like Dr. Michael S. Brown and Dr. Joseph L. Goldstein, who shared a Nobel Prize in Medicine in 1985, attention shifted to low density lipoprotein cholesterol, or L.D.L., the so-called bad cholesterol. When L.D.L. is oxidized, it becomes glued to the lining of arteries that feed the heart, brain and tissues throughout the body, setting the stage for a heart attack, stroke or peripheral vascular disease.
A Sliding Scale of Safety
Based on current recommendations, people otherwise at low risk for heart disease should have an L.D.L. level of less than 130. For someone known to be at high risk or who already has heart disease, the desirable level of L.D.L. is much lower, well below 100.
The statin drugs have revolutionized the treatment of elevated L.D.L. These drugs are especially effective combined with a heart-healthy diet and regular exercise.
But the statins don't do much for the newest, and perhaps more important, focus of concern about cholesterol. It is the level of high-density lipoproteins, or H.D.L., a reverse carrier of cholesterol. H.D.L., often referred to as the good cholesterol, acts like an arterial Roto-Rooter, clearing cholesterol from blood vessels and routing it to the liver for elimination from the body.
Unlike L.D.L., which should be a low as possible, the higher the blood level of H.D.L., the better, even if it means raising your total cholesterol level above 200. Low levels of H.D.L. - below about 40 milligrams for men and 50 for women - are associated with an increased risk of cardiovascular disease. People with "longevity syndrome," who live into their 90's without evidence of heart disease, typically have very high levels of H.D.L.
There is considerable evidence linking an increased risk of heart disease and stroke more strongly to low H.D.L. levels than to high L.D.L. levels. For every one-milligram rise in H.D.L., the risk for developing cardiovascular disease falls by 2 to 3 percent. An H.D.L. level of 60 milligrams or higher helps to protect against this major killer.
In addition to enabling the body to get rid of unwanted cholesterol, H.D.L. acts in several other protective ways: as an antioxidant deterring the harmful oxidation of L.D.L., and as an anti-inflammatory agent, helping to repair what is now considered a major player in blood vessel disease. And it has anticlotting properties, which can help keep blood clots from blocking arteries.
Dr. Mark E. McGovern, chief medical officer at Kos Pharmaceuticals, regards H.D.L. as the most important new lipid treatment target. "The need for drugs to increase H.D.L. is compelling and urgent," Dr. McGovern wrote in the April issue of Postgraduate Medicine.
Raising Good Cholesterol
Statins do raise H.D.L. levels a little, perhaps 5 to 10 percent, but rarely enough to protect someone with low H.D.L. Other drugs now in use do a better job.
Most effective are the niacin-based medications (but not niacin sold as a vitamin). These high-dose prescriptions come in immediate-release form to be taken two to four times a day and in extended-release form taken once a day. Niacin can raise H.D.L. levels by 15 to 30 percent, and it is especially effective at increasing the larger H.D.L. particles that do the best job of cleansing arteries.
The other prescription drugs that can raise H.D.L.'s are fibrates, most often used to lower blood levels of artery-damaging fats called triglycerides. The fibrates, including gemfibrozil (Lopid) and fenofibrate (Tricor and Lofibra), raise H.D.L. by 10 to 15 percent.
Developing more effective drugs to raise H.D.L. is an important goal. Meanwhile, some doctors are prescribing statins in combination with a niacin or fibrate. This is not ideal, since combining statins with fibrates greatly increases the risk of muscle damage, a rare but potentially serious complication of statins. Statins with niacin may cause liver problems.
But you do not have to wait for the development of safer drugs to improve your cholesterol profile. Changes in the way you live can help to raise H.D.L.
Regular aerobic exercise is a good place to start. But for it to result in a significant benefit in H.D.L., about 1,200 calories a week should be expended on activities like brisk walking, jogging, cycling or lap swimming. For most people, that means walking briskly for three miles four times a week. Duration of exercise, not intensity, confers the greatest benefit.
If you are overweight, losing weight can raise your H.D.L. level. And if you are a smoker, quitting all forms of tobacco can increase your H.D.L. by 15 to 20 percent.
Dr. Peter P. Toth of the University of Illinois School of Medicine at Peoria says certain dietary measures also help. A Mediterranean-style diet, rich in fruits, vegetables, whole grains, olive oil and legumes, is strongly linked to high blood levels of H.D.L. So is eating more fish (and taking fish oil supplements) and consuming fewer refined carbohydrates.
A low-fat diet is not necessarily helpful. It may even lower H.D.L. levels if carbohydrates fill in the caloric gap. But the kinds of fats consumed can make a big difference.
Most helpful are the monounsaturated fats found in canola, olive, avocado, nut and seed oils; nuts and avocados. These can improve H.D.L. without raising L.D.L. But if you replace saturated fats with polyunsaturates like corn, safflower and soybean oils, both L.D.L. and H.D.L. levels are likely to fall.
Avoiding trans fats, formed when unsaturated oils are partly hydrogenated, is also important. These are found in many processed foods, especially snacks and packaged bakery items that contain added fats. Trans fats raise harmful L.D.L. and lower beneficial H.D.L.
Another helpful dietary measure is to increase the soluble fiber in your diet. Soluble fiber is found in fruits, vegetables, legumes and oats.
In addition, alcohol consumed in moderation, helps to raise H.D.L.'s. Consuming one or two drinks a day can increase H.D.L. levels significantly. Beyond that amount, alcohol can have harmful effects on the heart and increase cancer risk.
original story posted at http://www.nytimes.com/2005/06/28/health/nutrition/28brod.html?8hpib
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