- Cocoa (Theobroma cacao)
- Coronary Artery Disease
Re: Review of the Effects of Cocoa and Chocolate on Coronary Heart Disease
O, Gaziano JM, Djoussé L. Chocolate and coronary heart disease: a systematic review.
Curr Atheroscler Rep. 2011 Sep 6;
[Epub ahead of print]. doi: 10.1007/s11883-011-0203-2.
(Theobroma cacao) and chocolate have
been investigated for their beneficial effects on factors related to coronary heart
disease (CHD); however, it is unclear whether the actual risk of CHD is
affected. This article reviews the evidence for an effect on clinical and
subclinical CHD, CHD risk factors, and biological mechanisms, as well as the
limitations of the literature and suggested future directions. The authors
reviewed 7 studies that included 2 cross-sectional studies (7187 participants),
2 cohort studies (2385 participants), 1 randomized, single-blind trial (35
participants), 1 prospective study (470 participants), and 1 case-controlled
study (77,923 participants).
Chocolate is made
from the seeds of the cacao tree and is a combination of cocoa solids, cocoa
butter or other fats, and sugar. Milk chocolate also contains milk, while dark
chocolate contains added fat and sugar. [Editor's Note: What makes dark
chocolate dark is that it contains more cocoa solids than milk chocolate and no
milk.] White chocolate consists primarily of cocoa butter, sugar, and milk, and
does not contain any cocoa solids or flavonoids. Cocoa contains polyphenols and
flavonoids, in particular epicatechin, at a rate of 18-24 μg of epicatechin/100
g in milk chocolate, and 52-125 μg/100 g in dark chocolate. Chocolate also
contains saturated fat (60%), monounsaturated fat (35%), and linoleic acid
between chocolate/cocoa consumption and CHD prevalence, cardiovascular disease
(CVD), and all-cause mortality are examined in a number of studies. The
cross-sectional National Heart, Lung, and Blood Institute (NHLBI) Family Heart
Study in 4,970 subjects showed an inverse relationship with prevalent CHD for those
who consumed chocolate ≥5 times per week (odds ratio [OR] of 0.43; 95%
confidence interval [CI], 0.28-0.67). A second study reported a 35% reduced
risk of CVD with consumption of chocolate ≥1 time per week (multivariable
adjusted relative risk [RR] of
0.65 [95% CI, 0.46-0.94]).
In subclinical heart
disease, a single-blinded, randomized trial in 39 men showed improved coronary
flow velocity reserve in those who ate flavanol-rich dark chocolate (CFVR; 3.38
± 0.49 before and 4.28 ± 0.85 after dark chocolate intake; P<0.01), but showed
no improvement in those who ate white chocolate. A cross-sectional study (NHLBI
Family Heart Study) found an association between chocolate consumption and
calcified atherosclerotic plaques in coronary arteries in 2,217 participants
for chocolate consumption of 1-3 times per month, once per week, and ≥2 times
per week (OR of 0.94 [95% CI, 0.66-1.35], 0.78 [95% CI, 0.53-1.13], and 0.68
[95% CI, 0.48-0.97], respectively), compared to no chocolate intake for the
With respect to CHD
mortality, Janszky et al.1 observed
a strong inverse association in post-myocardial infarction patients for those
who consumed chocolate less than once per month, up to once per week, and twice
or more per week (hazard ratio [HR] of 0.73 [95% CI, 0.41-1.31], 0.56 [95% CI,
0.32-0.99], and 0.34 [95% CI, 0.17-0.70], respectively). A similar association
was found in the Iowa Women's Health Study after 13 years of follow-up in
postmenopausal women. Buijsse et al.2 reported an RR of 0.50 (95% CI, 0.32-0.78) for cardiovascular
mortality and an RR of 0.53 (95% CI, 0.39-0.72) for all-cause mortality in
elderly men when comparing the highest to the lowest tertile of
cocoa intake. Another
study in postmenopausal women by Mink et al.3 showed an RR of 0.90
(95% CI, 0.86-0.95) for incident CHD, and 0.88 (95% CI, 0.82-0.96) for total
mortality for the highest to the lowest quintile of flavanone consumption.
Decreased cardiovascular-related deaths were also noted in an observational
study in which subjects consumed cocoa as their main beverage.
involved could include 3 actions: (1) antioxidant activity that would reduce
oxidative stress, (2) improvement of endothelial function of blood vessels via
increase of nitric oxide (NO), and (3) increased intracellular free calcium
concentration and activation of endothelial estrogen receptors. Vasomotor
function was improved by 47% in a randomized, controlled, double-blind,
crossover study comparing the effect of high- and low-flavanol chocolate given
to 16 CHD patients for a month. An increase in the number of endothelial
progenitor cells, which are responsible for repair of damaged vasculature, was
Effects on blood
pressure (BP) were studied by Grassi et al.4 in hypertensive
patients with impaired glucose tolerance, showing a 3.83 mmHg decrease in
systolic BP and 3.92 mmHg decrease in diastolic BP in those consuming high-flavanol
chocolate compared to those consuming white chocolate. A possible mechanism of
action was brought to light in a study showing inhibition of
angiotensin-converting enzyme (ACE) activity and increased NO in human
endothelial cells (P<0.01) after consumption of dark chocolate. Another
study showed no effect of 70% cacao dark chocolate (50 g/day) on BP. A
meta-analysis concluded that chocolate causes a mean change in systolic BP of -3.2
± 1.9 mmHg and diastolic BP of -2.0 ± 1.3 mmHg (P=0.003).
have also been explored. One study using dark chocolate reported a decrease in
total cholesterol (-6.5%; P<0.0001) and low-density lipoprotein (LDL)
cholesterol (-7.5%; P<0.0001), with no effect on serum high-density
lipoprotein (HDL) cholesterol, or triglycerides (TG). Another study also showed
a decrease in cholesterol along with an increase in HDL cholesterol (1.16 ± 0.08
vs. 1.26 ± 0.08 mmol/L; P=0.05). A meta-analysis by Jia et al.5 for
short-term chocolate consumption concluded that it lowered LDL cholesterol by
5.87 mg/dL and total cholesterol by 5.82 mg/dL, but that this was highly
dependent on the amount of cocoa consumed and health status of the patients (no
effects were observed in healthy participants). A second meta-analysis showed
that dark chocolate was associated with a reduction in serum LDL (-5.90 mg/dL [95%
CI, -10.47 to -1.32]) and total cholesterol (-6.23 mg/dL [95% CI, -11.60 to -0.85]),
but not with an increase in HDL cholesterol or TG.
was decreased after consumption of flavanol-rich dark chocolate (P<0.0001),
along with enhanced insulin sensitivity (P<0.05) and improved beta-cell function
(P=0.035), compared to no effect for white chocolate. A second study also saw
an improvement in insulin resistance (0.31% reduction).
Reduction in platelet
aggregation has also been reported in one study following 100 g of dark chocolate
consumption. A possible mechanism of action could be reduced adenosine
diphosphate (ADP)/collagen-activated platelet-related primary hemostasis due to
a reduction in activated glycoprotein IIb/IIIa surface proteins.
According to the
authors, the existing literature, while showing effects, has the limitations of
short duration of studies; lack of clear notation of type or amount of
chocolate used, or separation of dark and milk chocolate, which may have led to
an underestimation of effects; lack of clarity of optimal intake level; lack of
recording of polyphenol content; and heterogeneity of studies making
Future studies should
pay attention to these factors, as well as to separating out lifestyle factors.
The authors conclude by noting that, "Long term, double-blind, randomized
controlled trials with hard clinical endpoints are needed before recommending
cocoa or its products as a treatment option in patients with high risk for CHD
or for healthy individuals. In the meantime, it would be safer to consume dark
chocolate only in moderate amounts."
I, Mukamal KJ, Ljung R, Ahnve S, Ahlbom A, Hallqvist J. Chocolate consumption
and mortality following a first acute myocardial infarction: the Stockholm Heart
Epidemiology Program. J Intern Med.
B, Feskens EJ, Kok FJ, Kromhout D. Cocoa intake, blood pressure, and
cardiovascular mortality: the Zutphen Elderly Study. Arch Intern Med. 2006;166(4):411-417.
Scrafford CG, Barraj LM, et al. Flavonoid intake and cardiovascular disease
mortality: a prospective study in postmenopausal women. Am J Clin Nutr. 2007;85(3):895-909.
4Grassi D, Desideri G,
Necozione S, et al. Blood pressure is reduced and insulin sensitivity increased
in glucose-intolerant, hypertensive subjects after 15 days of consuming
high-polyphenol dark chocolate. J Nutr.
5Jia L, Liu X, Bai YY,
et al. Short-term effect of cocoa product consumption on lipid profile: a
meta-analysis of randomized controlled trials. Am J Clin Nutr. 2010;92(1):218-225.