Cholesterol is a type of lipid that performs several functions in the body, including maintaining cell membrane structure, insulating nerve fibers, production of bile acids and synthesis of steroid hormones. The American Heart Association, or AHA, notes that high cholesterol levels are one controllable risk factor of cardiovascular disease. The "great cholesterol myth" refers to a debate led by a few scientists that disagree that high cholesterol levels are linked to cardiovascular disease.
Risk Factors
Much of this argument can be cleared up by defining a risk factor, which is any factor in the environment, diet or family history that increases the likelihood of developing a disorder or disease. A particular risk factor might be linked to the disease, but might not necessarily play a role in causing the disease. Additionally, a risk factor might be more applicable to one population than another. A review in the November 2002 issue of the "International Journal of Epidemiology" reports that the major risk factors for cardiovascular disease are high blood cholesterol, high blood pressure, a sedentary lifestyle and cigarette smoking, and that these factors account for at least 75 percent of all cases of heart disease. Additionally, if a person has more than one risk factor, he is at a higher risk for developing cardiovascular disease.
Cholesterol Controversy
The most outspoken scientist on the "great cholesterol myth" is Uffe Ravnskov, a Russian doctor and research scientist. He argues that cholesterol is an essential molecule in the body that serves several functions, is primarily produced in the liver and that levels are not markedly altered by dietary consumption, nor are they linked to heart disease. There is general agreement that cholesterol is required in the human body, but the AHA and other organizations, such as the National Heart Lung and Blood Institute, or NHLBI, report that physical activity and diet do affect cholesterol levels and that in many populations, high cholesterol is a primary risk factor for cardiovascular disease. The evidence for their conclusions is based on a large body of scientific evidence, including epidemiological studies, clinical studies and laboratory studies.
Cholesterol and Atherosclerosis
Atherosclerosis is a chronic disease that begins early in life that precedes the development of detectable cardiovascular disease. It is a slow process that gradually hardens the arteries and makes them narrower. To function in all areas of the body, cholesterol is transported from the liver to other sites by carrier molecules, which are predominantly low density lipoproteins and high density lipoproteins, commonly referred to as LDLs and HDLs, respectively. In the progression of atherosclerosis, LDL cholesterol sticks to compromised areas of blood vessels and contributes to plaque formation. Plaques are formed by LDL cholesterol, immune system cells, fatty acids and calcium deposits. The National Cholesterol Education Program reports that several clinical trials provide conclusive evidence that lowering the level of LDL cholesterol significantly decreases the progression of atherosclerosis and reduces heart attacks and coronary heart disease.
National Recommendations
The AHA says people with total cholesterol levels above 240 mg/dL have a two-fold higher risk for developing cardiovascular disease. Also, a level of LDLs above 130 and HDLs below 50 mg/dL for women and 40 mg/dL for men are linked to an increased risk of cardiovascular disease. One argument put forth in the "cholesterol myth" is that statins and other cholesterol-lowering drugs have little effect on cholesterol levels or cardiovascular disease risk. However, according to a review in the July 2004 issue of "Circulation," several clinical trials suggest otherwise. Also, the AHA and NHLBI not only recommend drug therapy for lowering cholesterol levels and preventing cardiovascular disease, but also highly encourage dietary and physical activity changes as an integral part of cardiovascular disease reduction.
References
- American Heart Association: Cholesterol
- "International Journal of Epidemiology"; "The Search for New Risk Factors for Coronary Heart Disease: Occupational Therapy for Epidemiologists"; Robert Beagleholea and Paul Magnus; November 2002
- "Fat and Cholesterol are GOOD for You! What REALLY Causes Heart Disease; Uffe Ravnskov"; GB Publishing; January 2009
- American Heart Association: What Your Cholesterol Levels Mean
- National Heart Lung and Blood Institute: National Cholesterol Education Program
- "Circulation"; "Implications of Recent Clinical Trials for the National Cholesterol Education Program Adult Treatment Panel III Guidelines"; Scott Grundy et al; July 2004
