Poręba R, Skoczyńska A, Gać P, et al. Drinking of chokeberry juice from the ecological farm Dzięciołowo and distensibility of brachial artery in men with mild hypercholesterolemia. Ann Agric Environ Med. 2009;16:305-308.
The
activities of nutritionally active substances, such as polyphenols, have been
shown to play a protective role in the cardiovascular system. For example, the
anthocyanins in polyphenolic compounds have an anti-sclerotic effect because of
their anti-inflammatory, antioxidant, hypolipemic, and hypoglycemic properties.
Furthermore, anthocyanin consumption has been shown to decrease blood pressure
in middle-aged men and in patients with hypertension or metabolic syndrome. Chokeberry
(Aronia melanocarpa) fruit, which is widely
used in juice and wine production, is rich in polyphenols and anthocyanins and
has recently been shown to have an anti-atherosclerotic effect. The first stage
in the development of atherosclerosis involves endothelial dysfunction, which
is evaluated on the basis of brachial artery dilation (BAD). The objective of
the present study was to assess the influence of chokeberry juice consumption
on endothelial function and on nitric oxide (NO) levels in mildly
hypercholesterolemic men.
Thirty-five
mildly hypercholesterolemic men (i.e., total serum cholesterol: > 200 mg/dL)
with no history of pharmacologic treatment to lower cholesterol levels were
enrolled in the present study. The subjects had a mean age of 53.9 years and a
mean body mass index of 27.4 kg/m2. The subjects consumed 250 mL of
chokeberry juice daily. Endothelial function (based on measurements of brachial
artery diameter via flow-mediated dilation [FMD]), serum lipids (triglyceride
and total, high-density-lipoprotein, and low-density-lipoprotein [LDL] cholesterol
levels), and NO levels were measured at the beginning of the study (I), after 6
weeks of regular consumption of the juice (II), after 6 weeks of abstaining
from juice consumption (III), and then again after another 6 weeks of regular consumption
of juice (IV). The juice was obtained from the Dzięciołowo farm in
Significant
decreases in serum total cholesterol, LDL cholesterol, and triglycerides were
observed, according to the authors. No significant differences in high-density-lipoprotein
cholesterol were observed between the 4 measurement time periods. Significant
increases in serum NO were observed. FMD increased significantly during the
study.
At the
beginning of the study, 13 of the 35 subjects (37.1%) had a FMD ≥ 7%,
regarded as standard; after 6 weeks of juice consumption, 29 of the 35 subjects
(82.9%) had a FMD ≥ 7%; and after 6 weeks of abstaining
from juice consumption followed by an additional 6 weeks of consumption, all 35
subjects had a FMD ≥ 7%. Mean FMD values increased
progressively over each period from 6.54% at baseline to 9.56%, 10.83%, and
11.04%, respectively. In addition, the consumption of chokeberry juice for 6
weeks and then for an additional 6 weeks after a 6-week pause in consumption
resulted in a significant decrease in serum lipid concentrations in mildly
hypercholesterolemic men. The authors concluded that "regular drinking of
chokeberry juice has a beneficial effect on endothelial function and lipid
metabolism in men with mild hypercholesterolemia."
—Brenda Milot, ELS
Peer
Reviewer Comments:
While the authors'
conclusions are technically true, the conduct and analysis of this trial are
problematic, making interpretation of these results difficult. The major
problem has to do with the complete lack of controlling for multiple testing. First,
a specific primary endpoint should have been named but was not. FMD Max % is
standard for such studies, but the authors list 2 others (BAD and NO). Furthermore,
they list 4 cholesterol endpoints and do not distinguish them as secondary. Finally,
there are 4 time points yielding 6 possible tests for each parameter.
These authors should
have reported the ANOVAs for each parameter AND reduced the p-value for
significance based on the number of parameters they wanted to test. Then, they
should have predetermined which time point pairs they wanted to test if the
ANOVA was significant, AND reduced the p-value for significance for the number
of tests they performed. As reported, the only p-values that might be
interesting are ones P<0.001 (i.e., FMD% between baseline and after
baseline); BAD and FMD are highly correlated.
While 35 participants
in an FMD study is typically enough to detect meaningful changes, unexplained
is what appears to be no change in NO, which is typically considered the
mediator of FMD. One might expect NO to increase after consumption, decrease
when stopped, and then increase; the elevation between time points 1 and 4 may
simply be spurious.