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Antioxidants
Antioxidants are, just as they sound, chemicals that prevent the oxidation of other compounds.
Oxidation
Oxidation is the process of adding oxygen to a compound. Think “rust.” This process, left unchecked,
can produce “free radical” molecules. Free radicals can initiate chemical reactions that can cause
damage to cells and DNA.
Scientists are only beginning to understand the complexity of free radical damage.
Oxidation occurs in our bodies naturally, but can be intensified by certain behaviors
such as smoking, poor diet, exposure to sun (UV radiation), and even exercise.
Antioxidant Activity
“Anti”-oxidants typically reduce the level of these
free radicals by acting as recipients of the extra oxygen
thus preventing the oxidation and subsequent damage.
In Foods and In Our Bodies
Our bodies can mount defenses against this oxidation but this ability declines with age.
One way to enhance our body’s antioxidant defenses is to eat antioxidant-rich foods.
A few plant-based foods including apples, onions, soybeans, blueberries,
cranberries, teas (green and black), red wines and dark chocolate are
distinguished by their high polyphenol content.
Polyphenols are found in many fruits, vegetables and whole grains.
You are probably familiar with the red and purple colors of berries.
These colors come from anthocyanins—a subclass of polyphenols.
Another sub-class of polyphenols is the colorless flavanols
(or more precisely flavan-3-ols) found in cocoa and some other
plant-derived foods. (Figure 1)
Figure 1
Measuring Antioxidants in Food
ORAC, or Oxygen Radical Absorbance Capacity is a measure
of antioxidant power. This measure quantitates a food’s
ability to neutralize the harmful effects of free radicals.
More research is needed to fully understand how ORAC
values for food relate to antioxidant activity in the
body after the food is consumed. Data from the U.S.
Department of Agriculture and the Journal of the American
Chemical Society indicates that dark chocolate tops the
list for ORAC on a per serving basis (Figure 2).
Data from The Hershey Company further indicates
that most cocoa-containing products contain natural
flavanols. Generally, the higher the concentration
of cocoa; the more flavanols are in the product.
Dark and baking chocolates tend to be much higher
in flavanol content than milk chocolate due to higher
cocoa content in the product. Natural cocoa refers
to non-alkalinized cocoa. The process of alkalinization
or “Dutching” cocoa significantly reduces the amount
of flavanols in cocoa.
Figure 2. ORAC per serving of foods which contain antioxidants.
(Gu, 2005; Wu, 2004; Hershey (internal data), 2005)
Health Benefits of Cocoa Flavanols
Many short term studies have suggested that
consumption of products containing cocoa may
provide cardiovascular benefits. The
strong in vitro (compounds studied in test
tubes) evidence of dark chocolate, cocoa and
cocoa components in improving cardiovascular
health led to a number of confirming clinical
trials in humans volunteers. However, it is
important to note that this research is in the
preliminary stages. More research including
longer term studies will be needed. Eating cocoa
and chocolate should not be considered a
substitute for medications or your doctor’s
advice. It is also important to note that many
chocolate products can be high in calories and
fat and should be consumed in moderation.
See hersheyskitchens.com for
recipe ideas using HERSHEY'S Cocoa.
Cholesterol: One factor of concern during clinical
studies was whether ingestion of large amounts of dark
chocolate, which contains saturated fat, would lead to
elevated serum cholesterol. However, it was found that
the fat from cocoa butter is mainly comprised of stearic
acid which has a neutral effect on serum cholesterol
(Weisburger, 2001). Thus far, most studies on cocoa and
chocolate have found no changes in cholesterol. However
these studies have either tested people with normal
cholesterol and/or were too short and too small to
determine such effects. A 4-week study combining cocoa
and dark chocolate found significant improvements in
HDL-cholesterol (Wan, 2001), while another found that
total cholesterol and LDL cholesterol levels were lowered
following the consumption of 100g of dark chocolate
for 15 days (Grassi, 2005a).
Both cocoa and dark chocolate have shown promising
results relating to a damaging type of blood cholesterol—oxidized
LDL cholesterol. A number of studies have shown that
consumption of a cocoa-based beverage for durations
varying between 2-4 weeks results in a delay in the
onset of LDL-oxidation (Wan, 2001; Kondo, 1996;
Osakabe, 2001, Osakabe, 2002). Another study showed a
dose-response effect speculating the greater amount of
flavanols ingested, the greater the effect on reducing
oxidized LDL formation (Wang, 2000).
Platelet Activity: Platelets are important
for wound healing and carrying blood clotting factors.
However in the inner lining of the endothelium, platelets
can aggregate (clump) and adhere to the site of an injury
(caused by LDL cholesterol or other factors in blood) and
subsequently contribute the development of plaques.
A decrease in platelet activity is favorable to overall
cardiovascular health. Currently, a few clinical trials
have investigated the effects of cocoa and platelet activity.
After drinking cocoa high in polyphenols, a reduction platelet
activation was found, as was a decreased formation of platelet
“microparticles”—which are linked to the development of
blood clots. The researchers concluded that eating
cocoa had an “aspirin-like” effect on blood-clotting
mechanisms (Rein, 2000).
Eicosanoid “Aspirin-like” Effects:Low-dose aspirin
therapy has been recommended for individuals at risk of
cardiovascular disease because aspirin reduces the production
of certain prostaglandins involved in the inflammatory
response. Because cocoa consumption is linked to the
production of the anti-inflammatory prostaglandin,
prostacyclin, an experiment was designed to compare
cocoa and low-dose aspirin administration. Platelet
functions were measured following the administration of
low dose (baby aspirin (81mg)), 300ml (~10 oz) of cocoa
beverage and a combination. The cocoa treatment demonstrated
an inhibitory effect on platelet activation and function.
The observed effect was slightly less than the baby aspirin
treatment, while the combination produced slightly better
results, especially related to microparticle formation,
than each alone (Pearson, 2002). Although, the increase
with cocoa was less than that seen with aspirin, it does
indicate that cocoa may be associated with a short-term
reduction in platelet reactivity, which in turn may
reduce the risk for formation of clots (Pearson, 2002).
High-Blood Pressure. Two studies have tested
cocoa or dark chocolate consumption in people with high
blood pressure. In one study, both systolic and
diastolic blood pressure were reduced following
ingestion of flavanol-rich cocoa for 14 days
(Taubert, 2003). The other found similar results
after 15 days of feeding 100g of dark chocolate
(Grassi, 2005a). Two studies have reported blood
pressure values for individuals with normal blood
pressure fed cocoa or chocolate. One study found
that dark chocolate reduced blood pressure, yet
still in the normal range. White chocolate has
no effect (Grassi, 2005b). The other study noted
no effect on blood pressure in their healthy
study population after ingestion of flavanol
rich cocoa (Fisher, 2003).
Endothelial Function/Nitric Oxide: Endothelial function
refers to the arterial ability to dilate and constrict under
various circumstances. This function plays an important role
in the development of many types of cardiovascular disease
and diabetes. Poor endothelial function correlates strongly
with cardiovascular disease, but can be reversed. Although
there are many serum markers of cardiovascular risk, endothelial
function testing may represent a better measure of the overall
effect susceptibility to cardiac events. Dietary compounds,
especially those with known antioxidant activity, have been
shown to have pronounced effects on endothelial function (Vita, 2005).
Investigations into cocoa and endothelial function have been
conducted. Two studies testing dark chocolate or cocoa found
significant improvement in overall function of the endothelium
in healthy volunteers (Engler, 2004; Heiss, 2003). Another
study investigated this effect in participants with high blood
pressure and found 100g of dark chocolate fed for 15 days to
produce significant improvements in endothelial function as
well as other health factors related to insulin resistance
and blood pressure (Grassi, 2005a).
Perhaps the most interesting and meaningful aspect of
endothelial function tests is the underlying physiological
mechanism which is influenced by cocoa flavanols. Nitric
oxide is produced in the endothelium and acts as a signaling
molecule for arteries to properly dilate when necessary.
The discovery of this effect was awarded the 1998 Nobel Prize
for Medicine and is the basic mechanistic premise for
pharmaceuticals designed for vascular disorders.
Fisher and colleagues were able to determine, via the use
of nitric oxide inhibitors, that the endothelial improvements
associated with cocoa flavanols were mediated via
nitric oxide (Fisher, 2003). Enhanced blood flow,
via enhancements in nitric oxide, have been linked
to improved cognitive, cardiovascular and reproductive
health (Fisher, 2003).
Conclusion:
1. Cocoa is a natural source of flavanols.
2. All natural (non-dutched) cocoa-containing products
contain flavanols, but in varying amounts depending mostly
on the amount of natural cocoa in the product.
3. Emerging evidence from in vitro studies and
human clinical trials show promising findings.
4. Longer-term studies are needed to determine
how consumption of cocoa and its components affect
the prevention or development of chronic disease.
5. Cocoa and chocolate should not be considered a
substitute for medications or your doctor’s advice.
References
Engler MB, et al. Flavonoid-rich chocolate improves
endothelial function and increases plasma epicatechin
concentrations in healthy adults. J Am Coll Nutr 2004 23: 197-204.
Fisher ND, et al . Flavanol-rich cocoa induces nitric-oxide-dependent
vasodilation in healthy humans. J Hypertens 2003 21:2281-6.
Grassi D, et al. 2005a. Cocoa reduces blood pressure and insulin
resistance and improves endothelium-dependent vasodilation
in hypertensives. Hypertension 2005 46: 1-8.
Grassi D, et al. 2005b. Short-term administration of dark chocolate
is followed by a significant increase in insulin sensitivity
and a decrease in blood pressure in healthy persons.
Am J Clin Nutr 2005 81:611-4.
Gu L, et al. Procyanidin (PC) content and total antioxidant
capacity (TAC) of chocolate and cocoa products.
FASEB J 2005;19:A1032:Abstract#598.20.
Heiss C, et al. Vascular effects of cocoa rich in flavan-3-ols.
JAMA 2003 290:1030-1.
Kondo K et al. Inhibition of LDL oxidation by cocoa. Lancet 1996 348:1514.
Osakabe N et al. Catechins and their oligomers linked by C4 - C8
bonds are major cacao polyphenols and protect low-density lipoprotein
from oxidation in vitro. Exp Biol Med 2002 227:51-6.
Osakabe N et al. Daily cocoa intake reduces the susceptibility
of low-density lipoprotein to oxidation as demonstrated in
healthy volunteers. Free Radic Res 2001 34:93-9.
Pearson DA et al. The effects of flavanol-rich cocoa and
aspirin on ex vivo platelet function. 2002. Thromb Res 106 :191-7.
Rein D et al. Cocoa inhibits platelet activation and function.
Am J Clin Nutr 2000 72 :30-5.
Taubert D, et al. Chocolate and blood pressure in elderly
individuals with isolated systolic hypertension. JAMA 2003 290:1029-30.
Vita JA. Polyphenols and cardiovascular disease: effects on endothelial
and platelet function. Am J Clin Nutr 2005 81:292S-7S.
Wan Y et al. Effects of cocoa powder and dark chocolate
on LDL oxidative susceptibility and prostaglandin concentrations
in humans. Am J Clin Nutr 2001 74 :596-602.
Wang JF et al. A dose-response effect from chocolate consumption
on plasma epicatechin and oxidative damage. J Nutr 2000 130 :2115S-9S.
Weisburger JH. Chemopreventive effects of cocoa polyphenols on
chronic diseases. Exp Biol Med 2001 226: 891-7.
Wu X, et al. Lipophilic and hydrophilic antioxidant
capacities of common foods in the United States.
J Agric Food Chem 2004;52:4026-37.
