Exercise is always one of the first recommendations for improving blood cholesterol levels, but do readily achievable amounts of exercise really improve HDL and LDL cholesterol?

A report in the Archives of Medicine describes a meta-analysis that looked at 35 clinical trials with a total of 1,404 participants and found that regular aerobic exercise increased HDL ("good") cholesterol by a mean of 2.5 mg/dL. This analysis did not examine the effects of exercise on LDL ("bad") cholesterol 

The participants' average exercise session lasted for about 40 minutes and they each did a total of 120 minutes of exercise a week. The rise in HDL cholesterol was not influenced by the intensity of the exercise, but the results suggested that a few longer periods of exercise were more effective than shorter exercise sessions. The response of HDL cholesterol was greater in individuals who were not obese and who had a total cholesterol of 220 mg/dL or higher.

But the increases in HDL cholesterol revealed by the meta-analysis — an average increase of 2.5 mg/dL — were by no means dazzling. Such an increase in HDL cholesterol is almost certainly beneficial, but since a man's HDL cholesterol level may commonly be as low as 30 mg/dL or less, a 2.5 mg/dL boost in HDL will still leave him far short of the minimal target of at least 40 mg/dL for men.

Two final points about exercise and cholesterol should not be obscured by this meta-analysis, which focused only on HDL levels.

• Despite ubiquitous references to the ability of exercise to lower bad LDL cholesterol, regular exercise has little or no impact on LDL cholesterol levels.
• Exercise is an extremely effective way to lower triglyceride levels.