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- Cocoa (Theobroma cacao)
- Cardiovascular Disease Risk
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Date:
10-15-2013 | HC# 061312-482
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Re: Review of Cocoa Consumption Effects on Cardiovascular Disease Risk
Arranz S,
Valderas-Martinez P, Chiva-Blanch G, et al. Cardioprotective effects of cocoa:
Clinical evidence from randomized clinical intervention trials in humans. Mol Nutr Food Res. 2013;57(6):936-947.
Epidemiological
studies and some clinical studies have indicated that cocoa (Theobroma cacao) consumption is
associated with reduced risk of cardiovascular disease (CVD). These effects are
attributed to the polyphenolic content in cocoa (12-18% of dry weight),
especially the flavonoids. This review evaluates the effects of cocoa
consumption on various cardiovascular risk factors.
Cocoa
contains numerous flavonoids, including the monomeric flavan-3-ol epicatechin
(35% of total phenolic content) and the oligomeric and polymeric flavan-3-ols
known as procyanidins (58% of total phenolic content). The bioavailability of
these flavonoids depends on how these compounds are absorbed, metabolized, and
eliminated. Both food components (protein, fat, polysaccharides from milk or
other foods) and the gut physiology of individuals can also affect the
bioavailability of cocoa flavonoids.
There
is contradictory information about the effects of cocoa consumption on lipid
profiles. Cocoa intake reduced serum low-density lipoprotein cholesterol (LDL-c)
in hypertensive individuals, whereas dark chocolate intake had no effects on
cholesterol in healthy subjects; however, other research showed that both
healthy subjects and patients with high cholesterol had reduced LDL-c and
increased high-density lipoprotein cholesterol (HDL-c) after 4 weeks of cocoa
consumption. Chronic cocoa consumption also improved HDL-c levels and reduced
oxidized LDL-c. Moreover, a meta-analysis indicated that 2-12 weeks of cocoa
consumption improved LDL-c and total cholesterol (TC).
There
is less information available about cocoa effects and diabetes, another CVD
risk factor. In 3 clinical studies from the same investigators, it was found
that 100 g/day (88 mg flavanols) of dark chocolate for 15 days increased
insulin resistance in both healthy and hypertensive subjects with or without
glucose tolerance. On the other hand, different investigators showed that they
could not improve insulin sensitivity after 2 weeks of consumption of a cocoa
drink (900 mg flavanols) in patients with hypertension. Moreover, obese and
overweight subjects had increased insulin sensitivity from a high- flavanol cocoa
diet compared to a low-flavanol cocoa diet. Research also showed that insulin
sensitivity worked best in acute treatments (< 3 weeks).
Several
studies have also indicated cocoa flavonoids inhibit platelet aggregation. In
particular, procyanidin-rich cocoa lowered leukotrienes and increased levels of
prostacyclin compared to low-procyanidin cocoa. Other similar studies found
that cocoa products with high polyphenolic content (600-900 mg) were the most
effective at inhibiting platelet aggregation compared to cocoa products with
low polyphenolic content. Although the acute intake of polyphenolics appears to
be effective, other studies that assessed chronic intake of flavonoid-rich
diets did not reduce platelet aggregation.
Several
clinical studies evaluating vascular system effects showed that dark chocolate
consumption, but not white chocolate consumption, reduced blood pressure (BP)
in healthy subjects and patients with hypertension, glucose-intolerant hypertension,
or prehypertension or stage I hypertension. Even small amounts of
polyphenolic-rich dark chocolate reduced BP and improved the formation of the
vasodilator nitric oxide in patients with hypertension. Both solid dark
chocolate and liquid cocoa improved endothelial function and BP in overweight individuals;
however, some studies suggested that older individuals benefit less from cocoa
products due to their elevated levels of the vasoconstriction protein
endothelin 1.
Other
studies examining antioxidant activity have indicated that the flavanol content
of cocoa products are associated with increased plasma antioxidant activity,
prevention of LDL oxidation, and reduction of oxidative stress markers. The
consumption of cocoa products caused plasma antioxidant activity to peak at 1-2
hours and reduced LDL oxidation after 4-12 weeks in healthy subjects, as well
as decreased several markers of oxidative stress in short-term studies; however, other researchers have
indicated that oxidative biomarkers did not change in healthy subjects after 3 weeks
of white or dark chocolate intake or 2 weeks with high-flavonoid or low-flavonoid
chocolate.
Studies
have also showed that consumption of cocoa polyphenolics reduces inflammatory
markers associated with CVD. More specifically, studies have found reduced expression
of several inflammatory cytokines after cocoa consumption. In contrast, other research indicated
cocoa intake caused neutral effects or only reduced one of the inflammatory
cytokine markers. Moreover, high-sensitivity C-reactive protein (hs-CRP), a
well-established inflammatory biomarker, had an inverse linear effect with
cocoa flavonoids. Several studies also indicated that adhesion molecules
associated with inflammation were reduced after cocoa consumption, while other
studies showed no effects, especially when consumed with milk.
Regarding scientifically supported health
claims, the European Food Safety Authority (EFSA) has recently approved a
health claim for cocoa and circulation based on 16 human intervention studies. EFSA
concluded that a cause-and-effect relationship had been established between the
consumption of 200 mg of cocoa flavanols daily and the maintenance of normal endothelium-dependent
vasodilatation, and that this amount could be provided by 2.5 g of
high-flavanol cocoa powder or 10 g of high-flavanol dark chocolate. EFSA did
not approve claims regarding cocoa's effect on BP lowering or protection of
lipids from oxidative damage.
Overall,
this review suggests that the consumption of cocoa products, at various doses
and treatment durations, reduced several risk factors associated with CVD; however,
most studies assessed acute consumption of cocoa flavanols, and therefore, more
studies are needed to evaluate the long-term effects of cocoa intake, as well
as the potential cardiovascular effects of other cocoa phytochemicals.
—Laura M. Bystrom, PhD
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