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- Dark Chocolate (Theobroma cacao)
- Endothelial Function
- Cocoa
| Date: 08-31-2008 | HC# 080181-359 |
Re: Cocoa and Dark Chocolate Consumption Improves Endothelial Function in Healthy Adults
Faridi Z, Njike VY, Dutta S, Ali A, Katz DL. Acute dark chocolate and cocoa ingestion and endothelial function: a randomized controlled crossover trial Am J Clin Nutr. 2008;88: 58-63.
Dark chocolate (Theobroma cacao) consumption has been
shown to have cardiovascular health benefits, which are attributed to the
ability of the flavonoids in chocolate to improve endothelial function by
activating the nitric oxide synthase system, providing antioxidant effects, and
inhibiting platelet activation and aggregation. An impaired release of nitric
oxide causes endothelial dysfunction, i.e., vessels, to constrict and impede
flow in response to stimuli that should result in dilatation and flow augmentation.
Several studies have also shown that endothelial function is impaired after
glucose loading. Endothelial function can be determined noninvasively by
inducing hyperemic flow and sheer stress, which stimulates nitric oxide
release. High-resolution ultrasound is the standard method used to measure
endothelial-dependent flow-mediated dilatation (FMD) of the brachial artery.
The authors were unaware of any study that had compared the vascular effects of
liquid cocoa with those of dark chocolate or of regular cocoa beverage with
sugar-free cocoa; therefore, they compared the acute effects of solid dark
chocolate and those of regular and sugar-free liquid cocoa with the effects of
placebos on endothelial function and blood pressure in overweight adults.
Healthy men and women were
recruited from the Lower Naugatuck Valley
area of Connecticut
for this randomized, placebo-controlled, single-blind crossover study. Those
with an eating disorder, coronary artery disease, diabetes, or sleep apnea were
excluded, as were those who were pregnant, were following a restricted dietary
regimen, or were allergic to chocolate or cocoa. In phase 1 of the study, 45
subjects were randomly assigned to consume a single dose of either 74 g of a
solid dark chocolate bar (containing 22 g of cocoa powder) or 74 g of a placebo
bar (containing 0 g of cocoa powder). In phase 2 of the study, the subjects
were randomly assigned to consume a single dose of 1 of 6 sequence permutations
of sugar-free cocoa (2 cups containing 22 g of cocoa powder, sweetened with
small amounts of vanillin, acesulfame-potassium, and aspartame), sugared cocoa
(2 cups containing 22 g of cocoa powder, 45.3 g of sugar), or a placebo (2 cups
containing 0 g of cocoa powder), each prepared in 240 mL of hot water. The
placebos contained slightly more carbohydrates than the solid chocolate (39 g)
or the sugared cocoa (104 g). Each treatment was followed by a 7-day washout
period. Blood pressure was measured and endothelial testing and vascular
reactivity testing sampling were conducted at baseline (after the subjects
fasted overnight) and then 2 hours after each treatment. Endothelial function
was measured as FMD.
Forty-four subjects with a
mean age of 53 years and an average body mass index of 30 completed the study.
One was hypertensive, and 3 were dislipidemic; 4 were on medication that
included Lipitor, Avapro, Lotensin, and verapamil. No significant differences
in endothelial function and blood pressure were observed at baseline. In Phase
1, consumption of dark chocolate improved FMD more (4.3 ±
3.4%) than did the placebo (-1.8 ±
3.3%) (P < 0.001). Furthermore, systolic and diastolic blood pressure
decreased more after dark chocolate consumption than after placebo consumption
(P < 0.001). The findings remained the same after adjustment for age, race,
body mass index, hypertension, and dyslipidemia. In Phase 2, consumption of
sugar-free and sugared cocoa improved FMD (5.7 ±
2.6% and 2.0 ± 1.8%, respectively) more
than did consumption of the placebo (-1.5
± 2.8%) (P < 0.001). FMD
improved more after consumption of the sugar-free cocoa than after consumption
of the sugared cocoa (P < 0.001). Furthermore, both systolic and diastolic
blood pressure decreased more after consumption of the sugar-free cocoa than
after consumption of the placebo (P < 0.001). No significant differences in
blood pressure were observed after sugared cocoa consumption compared with
placebo.
The results suggest that
acute ingestion of solid dark chocolate and liquid cocoa significantly improves
endothelial function and lowers blood pressure in overweight but otherwise
healthy men and women. The effects were significantly greater after consumption
of sugar-free cocoa than after consumption of sugared cocoa. The improvement in
endothelial function was likely related to elevations in plasma epicatechin
concentrations, which increase endothelium-derived vasodilators. However, the
failure to measure the plasma catechin concentrations, or to provide equivalent
content of magnesium and methylxanthine alkaloids theobromine and caffeine in
the placebos as found in the chocolate and cocoa, does not allow the effects to
be attributed exclusively or even primarily to the polyphenols, since these
other components have potential vasodilating activity as well. Because the
antioxidant concentrations of the sugared and sugar-free cocoa preparations
were the same, the greater effects observed after consumption of the sugar-free
preparation are attributed to the absence of sugar. The authors suggest that
future studies are "clearly warranted to determine longer term effects of
habitual solid and liquid cocoa ingestion, optimal dosing of chocolate for
cardiovascular benefit, variation in beneficial effects among diverse
populations, and, ultimately, the influence of dietary cocoa intake on cardiac
events."
—Brenda Milot, ELS
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