Transcript Cacao Polyphenols - Pennington Biomedical Research Center

Cocoa Polyphenols
Pennington Biomedical Research Center
Division of Education
Heli Roy, PhD
Shanna Lundy, BS
Phillip Brantley, PhD- Chief
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Overview…
• An increasing body of epidemiologic evidence supports the concept
that diets rich in fruits and vegetables promote health and attenuate,
or delay, the onset of various diseases, including cardiovascular
disease, cancer, and certain neurodegenerative disorders
• Epidemiologic data has linked these health benefits, at least in part,
to the presence of certain flavonoids in fruits and vegetables
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Flavonoids…
• Flavonoids are a group of polyphenolic compounds that occur widely
in fruits, vegetables, tea, red wine, and chocolate
• Cocoa and chocolate products have the highest concentration of
flavonoids among commonly consumed foods
• Over 10 percent of the weight of cocoa powder is flavonoids
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• Cocoa and chocolate products have been delicacies for
hundreds of years
• Cocoa and chocolate have only recently have they been recognized
as significant sources of phytochemicals, with healthful effects
• Cocoa and chocolate are among the most concentrated sources of
the procyanidin flavonoids, catechin and epicatechin
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Chocolate Candy Consumption
• Americans eat a lot of chocolate in the form of candy
(about 4.6 kg/year per person or 10 pounds), but not as
much as people in some northern European countries
• In Switzerland, the country with the highest chocolate
consumption, it is estimated at 9.9 kg/year (22 pounds)
for each person
• Each candy bar contains about 210 calories, 13 g fat (7
of which is saturated), 23 g of carbohydrate, and 3 g of
protein
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Flavonoids in Chocolate
• Chocolate and cocoa are unique in the type of
flavonoids present
• The flavonoids in cocoa/chocolate, principally
catechin and epicatechin, exist in long polymers
• They contain two, three, or up to ten of the
catechin or epicatechin units linked, which is fairly
distinctive, since most flavonoid-rich foods tend to
have more catechins and epicatechins in dimers
or trimers, not pentamers, hexamers, etc
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Flavonoids in Chocolate
• Also intriguing is the chemistry of flavonoids in
cocoa which are really R-oligomers
• These structural characteristics of catechin and
epicatechin represent the molecular basis for both
their hydrogen-donating (radical-scavenging)
properties and their metal-chelating antioxidant
properties
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Flavonoid Content:
Is Variable
• As with most plants, genetic and agronomic factors can
markedly influence the contents of phytochemicals
available at the time of harvest
• Postharvest handling also plays a critical role, because
most cocoas undergo some fermentation steps, which
subject flavonoids in the cocoa to heat and acidic
conditions
• Subsequent processing steps, such as roasting and alkali
treatment, can also reduce the flavonoid contents
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Flavonoid Content
Is Variable
• The actual recipe for the finished food or beverage product
determines the amount of a given cocoa (and flavonoid) added.
• Depending on harvesting and processing procedures,
as much as 90% of the flavonoids can be lost during processing
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Flavonoid Content
• Different types of chocolate contain varying antioxidant content
• In finished products, the amount of cocoa ranges from
7% to 35% in milk chocolate and 30% to 80% in dark chocolate
• Consequently, the polyphenol content varies and is generally
twice as high in dark than in milk chocolate
• Also interesting is the fact that white chocolate does not contain
polyphenols
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Recent Studies
• Recently, Joe Vinson at the University of
Scranton (PA), who has been studying total
polyphenols in foods and beverages in the
American diet, has found even higher levels of
antioxidants in chocolate
• His studies have shown that on a weight basis,
“the concentration of polyphenols in milk
chocolate is higher than in red wines and black
or green teas. It is 20 times higher than in
tomatoes, 2 times higher than in garlic, and over
3 times higher than in grapes.”
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Foods High in Antioxidants
In addition to chocolate, the following foods and beverages are high in antioxidants:
• Beverages:
Tea (green and black), red wine, grape, tomato,
orange, and apple juice
• Top 10 vegetables: Garlic, kale, spinach, Brussels sprouts, alfalfa
sprouts, broccoli flowers, beets,
red bell peppers, onions, and corn
• Top 10 fruits:
Strawberry, plum, orange, red grapes, kiwi fruit,
pink grapefruit, white grapes, banana, apple,
tomato
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Numerous dietary intervention studies in humans and animals indicate
that flavanol-rich foods and beverages might exert cardioprotective
effects with respect to vascular function and platelet reactivity.
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Antioxidant Capacity
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Atherogenesis…
• Phenolic antioxidants have been
shown to inhibit the oxidation of lowdensity lipoprotein (LDL) cholesterol,
and mounting evidence suggests
that it is the oxidized form of LDL
that leads to the buildup of fatty
plaques in arteries
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Atherogenesis…
• Extracts of cocoa powder have also significantly inhibited LDL
oxidation in vitro
• Kondo et. Al. reported that cocoa prolongs the lag time of LDL
oxidation in a concentration-dependent manner
• Cocoa phenols has shown to inhibit LDL oxidation by 75%,
whereas red wines only inhibit LDL oxidation by 37-65%
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• Interestingly, cocoa powder and cocoa extracts have been shown to
exhibit greater antioxidant capacity than many other flavanol-rich
foods and food extracts, such as green and black tea, red wine,
blueberry, garlic, and strawberry in vitro
• However, no long-term studies have evaluated the effects of cocoa
polyphenol compounds on the oxidative modification of LDL in
humans
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Short-term human studies…
• Researchers set out to test whether or not these
effects shown from in vitro studies could be seen
in humans
• The levels of epicatechin and catechin were
measured in humans at zero, one, two, and six
hours following consumption of a single meal of
chocolate
• The concentration in plasma levels peaked at
about one hour; however, by six hours the
concentrations had almost disappeared from the
plasma
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Same
Effects
in studies…
Humans?
Short-term
human
• Indicated that cocoa flavonoids are absorbed and cleared
from circulation relatively quickly
• Support the recommendations to consume several
servings of fruit and vegetables per day as seen in a
number of clinical trials with chocolate and other
flavonoid-rich foods,
• Spacing intake of flavonoid-rich foods throughout the day
could help to provide a continuous supply
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More studies…
• Because there is six to seven times more epicatechin
than catechin in cocoa/chocolate, most attention has
focused on epicatechin in studies
• Consistent with in vitro studies, human studies
indicate that small doses of epicatechin are effective
• There is a statistically significant increase in plasma
antioxidant capacity and reduction in lipid peroxides
following cocoa/chocolate consumption
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Benefits…
• Epicatechin and other flavonoids not only have a
direct antioxidant effect, but they may also have a
sparing effect on other antioxidants such as
Vitamins C and E
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Other Mechanisms…
Although flavanol-rich cocoa and chocolate have the potential to
augment an individual’s antioxidant defense system, there are other
cellular mechanisms through which these flavanol-rich foods can
affect cardiovascular health:
Inflammation
Platelet aggregation
Nitric oxide (NO)-mediated endothelial changes
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Inflammation
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• Atherosclerosis and heart failure, as well as risk factors such as
hypertension and hypercholesterolemia, can activate several
proinflammatory enzyme systems, such as xanthine oxidase,
NADH/NADPH oxidase, and myeloperoxidase
• Once activated, these enzymes produce reactive oxygen species and
other radicals that, as indicated above, can modify NO availability
and LDL and contribute to endothelial dysfunction
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• Flavanol-rich cocoa liquor has been shown to stimulate NO
production and to significantly reduce the activities of xanthine
oxidase and myeloperoxidase after ethanol-induced oxidative stress
• In addition, cocoa flavanols and procyanidins may modulate other
mediators of inflammation
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Platelets
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• In addition to its influence on oxidative defense mechanisms,
polyphenols seem to benefit cardiovascular health in other waysthrough regulation of platelet reactivity
• Given the prominent role of platelets in the development and
manifestation of acute myocardial infarction, stroke, and venous
thromboembolism, antiplatelet strategies are an important
consideration
• A modest decrease in platelet reactivity can be of value because it
reduces the probability of clotting
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• In one study to determine whether cocoa inhibits platelet activation
and function, subjects were given either water or 300 ml of cocoa
that provided a very high amount of polyphenols
• During the six hour time period following intake of cocoa, there was a
reduction in P-selectin, suggestive of less reactive platelets
• This is the same response that would be seen following intake
of antiplatelet agents such as aspirin
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Endothelium
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• Shear stress, ischemia and reperfusion, inflammation, and
disease states, such as atherosclerosis, diabetes mellitus,
and hypertension, can disrupt endothelial function
• This is associated with alterations in endothelium-derived
regulatory mediators, an inability to regulate vascular tone,
and an overall shift toward the prothrombotic state
• Possible that flavanols, by functioning as antioxidants, in
addition to modulating prostacylin and leukotriene
concentrations, can improve endothelial function through the
prevention and possible reduction of oxidative damage
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Conclusions…
• Although in vitro studies provide strong support for the hypothesis
that flavanol-rich food consumption is associated with the reduced
risk for vascular diseases, at this time the majority of studies that
have been reported are in the form of short-term clinical trials
• The health benefits of these nutrients will best be determined from
long-term, randomized, clinical trials
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References
• Keen C, et al. Dietary polyphenols and health: Proceedings of the 1st
international conference on polyphenols and health. Amer J Clin Nutr.
2005. 81:1 298S-303S. Available at:
http://www.ajcn.org/cgi/content/full/81/1/298S
• Keen C. Chocolate: Food as medicine/medicine as food. J Amer Coll
of Nutr. 2001. 20:90005 436S-439S. Available at:
http://www.jacn.org/cgi/content/full/20/suppl_5/436S
• Wan Y, et al. Effects of cocoa powder and dark chocolate on LDL
oxidative susceptibility and prostaglandin concentrations in humans.
Amer J Clin Nutr. 2001. 74:5 596-602. Available at:
http://www.ajcn.org/cgi/content/full/74/5/596
References
• http://pubs.acs.org/hotartcl/tcaw/99/jul/chocolate.html
• http://sciweb.nybg.org/science2/pdfs/mb/chocolate.pdf#search='alter
native%20therapies%20sept/oct%20chocolate‘
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