Cardiovascular disease, the number-one cause of mortality for U.S. men and women, is a cluster of heart and blood vessel problems that are related to the development of atherosclerosis.
Atherosclerosis is a condition that progresses when plaque builds up on the walls of arteries. This buildup narrows the arteries, making it more difficult for blood to flow through them. Coronary heart disease (CHD) is a type of cardiovascular disease that includes atherosclerotic plaque buildup in the coronary arteries; angina pectoris (or chest pain); and heart attack.
High-density lipoprotein cholesterol (HDL-C) can be a negative risk factor for CHD. This can be confusing to grasp, but exercise professionals need to understand what it means and explain it to clients. A risk factor, which can be either positive or negative, is something associated with ill health. A positive risk factor enhances or promotes ill health. For example, smoking is a positive risk factor for CHD, as the risk for smokers is 2–4 times higher than it is for nonsmokers (American Heart Association 2011). A negative risk factor reduces or minimizes ill health. HDL-C levels above 60 milligrams per deciliter provide a protective effect against heart disease, thus reducing the risk. This is why HDL-C is referred to as the “good” cholesterol.
When designing clients’ exercise training and lifestyle behavior change plans, exercise professionals can incorporate several meaningful strategies that will raise HDL-C and thus serve as principal prevention measures to lower CHD risk. This article will explain the metabolic mechanism of HDL-C; specifically discuss its unique effects in women; and provide guidelines for raising HDL-C for clients who wish to lessen their risk of CHD.
Although the terms HDL and
Thus, while other lipoproteins deposit cholesterol, HDL-C helps to remove it from blood vessel walls where it has accumulated as plaque. The HDL particle comprises a cholesterol core surrounded by an outer shell of phospholipids (specific type of lipids attached to a phosphate group and nitrogen base) and apolipoproteins (proteins that bind to lipids). HDL particles are further classified into HDL2 and HDL3 subfragments. HDL2 is the larger of the two particles but has less density (weight). HDL2 is believed to be more active in the reverse cholesterol transport process (Eapen et al. 2009). It has been shown that in male and female adults with normal total cholesterol levels, the people with low HDL-C levels (less than 35 milligrams per deciliter [mg/dl]) have more cardiovascular events (such as heart attacks and unstable chest pain) than their counterparts with high HDL-C levels (Eapen et al. 2009). Moreover, for every 1 mg/dl increase in HDL, the risk for CHD drops 2% in men and 3% in women (Eapen et al. 2009). Commonly, premenopausal women have higher HDL cholesterol levels than men of the same age, owing to the women’s higher levels of estrogen.
CHD is the leading cause of death in American women (Eapen et al. 2009). Although statin therapy (lipid-lowering drugs that help reduce deaths from heart attack and stroke) is the primary intervention for CHD (in both women and men), 65%–75% of cardiovascular events still occur in adults who are taking these medications (Eapen et al. 2009). Therefore, there is a need for committed exercise professionals to offer clients other, nonpharmacological CHD interventions, most notably specific HDL-raising strategies.
According to Eapen and colleagues, several investigations have shown that low HDL-C levels are actually the best predictor of CHD risk in women, regardless of whether LDL-C (“lousy” cholesterol) levels and triglycerides (blood fats) are elevated or not. These authors point to data from the famous Framingham Heart Study, which showed that women whose HDL-C levels were in the lowest one-fifth had a relative risk for CHD three times higher than those whose levels were in the highest one-fifth. Estrogen, which reaches its peak during the childbearing years, usually raises HDL cholesterol.
Research indicates that menopause is particularly associated with large reductions in HDL-C levels (Eapen et al. 2009). In particular, during menopause there is a reduction in HDL2 particles, the more active subfragments in the reverse cholesterol transport pathway (Eapen et al. 2009). Thus, postmenopausal women experience a drop-off in the praiseworthy effects of HDL cholesterol.
A low HDL-C level is the most common cholesterol abnormality in people with CHD (Miller 2003). Exercise professionals are in a leading position to help clients combat this disease. Even as new medical modalities for raising HDL-C are tested and introduced, doing aerobic exercise and altering lifestyle behaviors are decisive and consequential interventions! See the sidebar “The Best Strategies for Raising HDL-C” for specifics.
Eapen, D.J., et al. 2009. Raising HDL cholesterol in women. International Journal of Women’s Health, 1, 181–91.
Kelley, G.A., Kelley, K.S., & Franklin, B. 2006. Aerobic exercise and lipids and lipoproteins in patients with cardiovascular disease: A meta-analysis of randomized controlled trials. Journal of Cardiopulmonary Rehabilitation, 26 (3), 131–44.
Kodama, S., et al. 2007. Effect of aerobic exercise training on serum levels of high-density lipoprotein cholesterol: A meta-analysis. Archives of Internal Medicine, 167 (10), 999–1008.
Miller, M. 2003. Raising an isolated low HDL-C level: Why, how and when? Cleveland Clinic Journal of Medicine, 70 (6), 553–60.