High-density lipoprotein (HDL) cholesterol levels can be improved through lifestyle changes. Nonpharmacologic approaches that are reported to be effective in increasing HDL serum cholesterol levels include weight control, specific dietary choices, increased aerobic exercise, smoking cessation and moderate alcohol consumption. Ginsberg discusses these nonpharmacologic approaches to increasing HDL levels by reviewing the pertinent literature.

A clear correlation exists between a high body mass index (BMI) and a decrease in serum HDL levels. Approximately 25 percent of men with a BMI of more than 30 have HDL levels of less than 35 mg per dL (1 mmol per L) compared with 7 percent in women with a BMI more than 30. The exact physiologic cause is unclear. Weight loss can result in increases of 4 to 6 percent in HDL levels, while weight gain decreases HDL levels by 3 to 5 percent. In persons trying to lose weight, no evidence exists to support the theory that weight cycling (weight loss and regain) is less desirable than no weight loss at all. The value of intense regular aerobic exercise in increasing serum HDL levels is clear, although the support for moderate exercise is less definitive.

Compared with the average American diet (37 percent fat with 16 percent saturated fat), dietary intervention decreased low-density lipoprotein (LDL) cholesterol levels and HDL levels by 7 percent following a diet of 30 percent fat with 9 percent saturated fat and by 11 percent following a diet of 26 percent fat with 5 percent saturated fat. The benefits of following a diet high in carbohydrates and low in fats remain controversial. Epidemiologic surveys suggest that a diet high in carbohydrates lowers the rate of coronary artery disease, but results from animal and human studies suggest that this dietary regimen may also increase serum triglyceride levels and decrease HDL levels. Lowering trans-fatty acid intake improves serum lipid levels, while a very-low-fat diet combined with stress-lowering lifestyle changes has been shown to result in regression of coronary artery disease.

Persons with a mild to moderate alcohol intake appear to have higher serum HDL levels, reduced rates of cardiovascular disease and lower mortality compared with persons who never drink alcohol; however, this advantage is offset in persons who drink heavily. Results from one four-year study demonstrated that moderate wine intake was associated with reduced mortality risk more than any other variable in the study (i.e., consumption of animal fats, vegetables, fruits). The alcohol, rather than the potential antioxidants or other factors in the wine, appeared to be responsible for this finding.

Cigarette smoking has been significantly associated with reduced HDL levels in men and women. Persons who smoke cigars or pipes, and those who have quit smoking cigarettes for more than one year, do not have lower HDL levels than those who do not smoke. Second-hand smoke also has been associated with lower HDL levels.

Ginsberg concludes that increased visceral fat, which is found more in men than in women, is inversely associated with HDL serum concentrations. Sustained weight loss is associated with higher HDL levels. A high-carbohydrate diet may lower HDL levels modestly; a diet high in monounsaturated fats may also lower HDL levels, but to a lesser degree. Moderate physical exercise appears to have little value, but intense regular aerobic exercise results in an increase in HDL levels. Moderate alcohol consumption increases HDL levels as does smoking cessation (see accompanying table).

editor's note: A low level of HDL cholesterol appears to be an independent predictor of coronary artery disease. The reverse cholesterol transport pathway allowing hepatic uptake of cholesteryl ester from HDL by the liver is better understood. The independence of this mechanism from the receptor-mediated uptake of LDL cholesterol adds to the impact of serum HDL levels. In addition, several components of HDL, including the proteins apolipoprotein A-1 and 2, appear to decrease formation of highly atherogenic oxidized LDL cholesterol. Lower levels of HDL cholesterol are associated with the severity of angiographically documented atherosclerotic coronary arteries in a dose-response manner. Low HDL concentrations also appear to be associated with increased rates of restenosis following percutaneous transluminal coronary angioplasty. Increasing the HDL level is becoming a higher priority, and methods of doing this need further exploration. The most recent report of the National Cholesterol Education Program (http://www.nhlbi.nih.gov/chd) identifies a low HDL cholesterol level as a coronary risk factor and recommends screening for all adults.—r.s.