Exercise may slightly boost "good"
cholesterol levels
Newswise —
Regular exercise appears to modestly increase
levels of high-density lipoprotein, or "good,"
cholesterol, according to a meta-analysis study
in the May 28 issue of Archives of Internal
Medicine, one of the JAMA/Archives journals.
A low level of
high-density lipoprotein cholesterol (HDL-C) is
an independent risk factor for cardiovascular
disease, the leading cause of death worldwide,
according to background information in the
article.
There is strong evidence that
individuals who are more physically active have
higher HDL-C levels. "Thus, the value of regular
aerobic exercise in increasing serum [blood] HDL-C
level and in reducing the risk of cardiovascular
disease has received widespread acceptance," the
authors write. "In contrast, results of aerobic
exercise studies vary considerably, depending on
the exercise program (e.g., duration, intensity
or frequency) and characteristics of subjects at
baseline."
Satoru Kodama,
M.D., of Ochanomizu University, Tokyo, and
colleagues performed a meta-analysis of 25
articles reporting the results of randomized
controlled trials that were published between
1966 and 2005 and assessed the effects of
exercise on HDL-C. To be included in the
analysis, the studies had to evaluate aerobic
exercise in adults with an average age of 20 or
older, specify HDL-C measurements at the
beginning and end of the study, have a length of
at least eight weeks, and randomly assign some
participants to a group of exercisers and others
to a control group of non-exercisers.
The 25
articles analyzed included a total of 1,404
participants with an average age range of 23 to
75 years and an average study period of 27.4
weeks. The exercise groups were told to exercise
for an average of 3.7 sessions per week at an
average of 40.5 minutes each, burning an average
of 1,019 calories per week.
In all the
studies combined, HDL-C increased by an average
of 2.53 milligrams per deciliter in the exercise
groups. The minimum amount of weekly exercise
that appeared necessary to change HDL-C levels
was 120 minutes or 900 calories burned. The
effect of exercise was greater in those who had
a higher total cholesterol level (220 milligrams
per deciliter or greater) and in those with a
body mass index of less than 28.
"In a previous
observational study, every 1-milligram per
deciliter increment in HDL-C level was reported
to be associated with a 2 percent and 3 percent
decreased risk of cardiovascular disease in men
and women, respectively," the authors write. "If
this observation were applied to our results,
the increase in HDL-C level by exercise
determined by this analysis would, by a rough
estimate, result in a cardiovascular disease
risk reduced by approximately 5.1 percent in men
and 7.6 percent in women. This is potentially of
substantial importance in public health,
although the effect of reducing cardiovascular
risk by increasing HDL-C level might be smaller
than that by use of medications such as fibrates
or niacin."
Only exercise
duration, and not frequency or intensity, was
associated with a change in HDL-C levels in the
analysis. When the participants exercised for 23
to 74 minutes per session, each 10-minute
increase in exercise duration corresponded to a
1.4-milligram per deciliter increase in HDL-C
level. "This suggests that in improving blood
HDL-C values, increasing time per session is
better than performing multiple brief exercise
sessions when total time for exercise is
limited, as is the case for many people," the
authors write.
