As if you needed another reason to eat chocolate, German
researchers have shown that ingesting types rich in cocoa
solids and flavonoids—dark chocolate—can fight
skin cancer. Their findings are preliminary because they
come from a trial of just 24 women who were recruited to
add cocoa to their breakfasts every day for about 3 months.
Half the women drank hot cocoa containing a hefty dose
of flavonoids, natural plant-based antioxidants that research
has suggested prevent heart attacks. The remaining volunteers
got cocoa that looked and tasted the same but that had relatively
little of the flavonoids. At the beginning and end of the
trial, Wilhelm Stahl of Heinrich-Heine University in Düsseldorf
and his colleagues conducted a host of tests on each volunteer.
One assessment involved irradiating each woman's skin with
slightly more ultraviolet (UV) light than had turned her
skin red before the trial began.
The skin of the women who had received the flavonoid-rich
cocoa did not redden nearly as much as did the skin of recruits
who had drunk the flavonoid-poor beverage. Women getting
the abundant flavonoids also had skin that was smoother
and moister than that of the other women.
Overexposure to UV light can foster the development of
skin cancer. A dietary source of skin protection might offer
some innate defense for sunny days when an individual doesn't
use sunscreen, Stahl's team says.
Why chocolate?
Chocolate, these scientists note, is just the latest in
a range of antioxidant-rich foods holding the potential
to shield skin from sun damage. For nearly a decade, Stahl's
group has conducted studies with cooked tomato products
showing that their ingestion, too, can limit UV-induced
skin reddening. Pigmented molecules called carotenoids—especially
the one known as lycopene—appeared responsible for
tomato's skin-protection benefit.
Many of the carotenoids in tomatoes are powerful antioxidants
that can quash free radicals. These are the molecular fragments
that can cause biological havoc when they rip electrons
from other molecules. Because many flavonoids also function
as potent antioxidants, Stahl's team decided to investigate
whether substances in chocolate might offer skin protection.
The researchers recruited women between the ages of 18
and 65. Each volunteer received packets of a dry powder
to mix each day with 100 milliliters of hot water—roughly
a half cup. Half of the women received powder containing
329 milligrams of flavanols, a type of flavonoid, per serving.
The rest got powder delivering a mere 27 mg of flavanols
per serving. The primary flavanols were epicatechin and
catechin.
Mars Inc., the candy company that has been experimenting
with dark-chocolate products rich in flavonoids, supplied
the cocoa powder and partially funded the experiment. Harold
H. Schmitz, the company's chief science officer, claims
that the proprietary recipe for the product retains nearly
all of the natural-cocoa flavonoids that most chocolate
processing cooks and washes out.
In the June Journal of Nutrition, Stahl's team
reports that the women drinking the high-flavonoid cocoa
had 15 percent less skin reddening from UV light after 6
weeks of cocoa consumption and 25 percent less after 12
weeks of the trial. Both figures are comparisons with the
same women's response to UV light before the study started.
The women drinking the cocoa with low flavonoids showed
no change during the trial.
Most flavonoids absorb UV light, and this probably played
a role in the skin effect, the researchers say. However,
they add, skin reddening is also an inflammatory response,
and other researchers have linked consumption of flavonoids
to ratcheting down the body's synthesis of inflammatory
agents.
For the women getting larger doses of flavonoids, blood
flow in the skin doubled over the course of the trial in
tissue 1 millimeter below the surface, and increased by
37.5 percent in tissue 7 to 8 mm deep. Similar improvements
in blood flow through big blood vessels have been witnessed
after people have eaten dark chocolate.
Moreover, after 12 weeks of consuming the flavanol-rich
cocoa, the women's skin was 16 percent denser, 11 percent
thicker, 13 percent moister, 30 percent less rough, and
42 percent less scaly than it was at the beginning of the
experiment. Although the mechanism for most of these benefits
remains unclear, the Düsseldorf researchers suspect
that improved blood flow was a contributor.
Mars' Schmitz agrees. "People don't think about it,
but in reality your skin, just like every other tissue,
depends on healthy blood flow. And in our previous work
... we showed that blood flow in the extremities—the
finger tip—was improved" in people receiving cocoa
flavonoids. So, he argues, "it wasn't a shot in the
dark" to hypothesize that cocoa ingestion might improve
overall skin condition and health. Yet, he adds, "I
was still surprised to see this."
If follow-up studies confirm these skin-health data, he
says, "you're talking about being able to make people
look better." He adds, "We did not go into this
study with the intention to create a skin-health product,
but it now looks like maybe we've got one."
Not just any chocolate
Could a person realistically add enough flavonoids to his
or her diet to produce the benefits suggested by the study?
Flavonoid quantities in the richer cocoa were "similar
to those found in 100 grams [a little over 3 ounces] of
dark chocolate," Stahl's group reports.
The cocoa drink provided its flavonoids in a serving that
delivered only about 50 calories—far below the 400
to 500 calories ordinarily encountered in candy providing
a walloping dose of flavanols. Schmitz concludes that people
can, in theory, get this efficacious dose without blimping
out.
The rub is that the cocoa used in this study and in others
by Mars isn't commercially available. If enough people pester
the company for the cocoa, Schmitz says, "eventually
we might have to offer such a product." In the meantime,
he notes, the company offers a candy, CocoaVia, in flavanol-rich
portions that deliver fewer than 100 calories per serving.
Targeting free radicals and more
The new skin-protection data are more than a curiosity,
says Hasan Mukhtar, director of dermatology research at
the University of Wisconsin–Madison. The results suggest,
he says, that dietary flavonoids reach the upper layers
of skin and "have the ability to counteract the oxygen
free radicals generated as a consequence of exposure to
UV radiation."
UV exposure leads not only to impaired immunity and accelerated
aging in skin, but also to cancer, especially in light-skinned
people, Mukhtar points out. Work by his group and others
has shown that UV light triggers many reactions in the body
that can lead to tissue damage.
In several papers, Mukhtar and his colleagues have found
evidence that natural botanical antioxidants—such as
those just tested in cocoa—can inhibit harmful, UV-triggered
chemical pathways in the body.
In a study at the Case Western Reserve University School
of Medicine, Mukhtar's group applied epicatechin-rich green-tea
flavonoids to the skin of volunteers before irradiating
the area with UV light. The researchers found that compared
with the response of unprotected skin, the tea cut by 60
to 80 percent DNA changes known to play a role in immune
suppression and skin cancer. The team noted that the treatment
also prevented sunburn.
In the March-April Photochemistry and Photobiology,
Mukhtar's team reports the results of treating cultured
skin cells with pomegranate fruit extract, a substance rich
in flavonoids. When irradiated with UV-light in a test tube,
human cells in such an experiment usually undergo stress-induced
inflammatory changes that can lead to cancer. However, the
pomegranate extract dramatically inhibited those pre-carcinogenic
changes.
Mukhtar points out that such data show that "not all
of these agents affect the same signaling pathways."
This suggests, he says, that eating a mix of flavonoid-rich
foods may reinforce the UV protection by simultaneously
acting on several potentially damaging processes. Some flavonoid
treatments may even prove additive in their skin-protecting
role, he says.
Chocolate's agents might offer important backup protection
to some of the substances his group has been testing, says
Mukhtar.
However, diet isn't the only means of getting these protective
agents to the tissues that need them, Mukhtar suspects.
He says it may make sense to add them to skin-care products.
That said, I'd prefer to get my protection from eating
dark chocolate. Indeed, I look for any excuse to label as
therapeutic my bittersweet indulgence.
