Researchers at the University of California demonstrated in the longest clinical trial to date that consuming dark chocolate rich in flavonoids every day improves blood vessel function over an extended period of time.
The university study, with a team of researchers led by Mary Engler, PhD, RN, divided 21 healthy adults into two groups. One group got a Dove Dark Chocolate bar every day for two weeks. This Dove chocolate bar has a high-cocoa content loaded with epicatechin. Epicatechin is a particularly active member of a group of compounds called plant flavonoids.
The second group didn't get Dove bars, but got dark chocolate bars with the flavonoids taken out.
All subjects underwent evaluation of how well the blood vessels dilate and relax -- an indictor of healthy blood vessel function. Blood vessel stiffness indicates diseased vessels and possible atherosclerosis. Those who got the full-flavonoid chocolate did significantly better. Blood tests showed high levels of epicatechin in their arteries.
"It is likely the elevated blood levels of epicatechin triggered the release of active substances that ... increase blood flow in the artery," Engler said in a 2004 news release. The findings appeared in the June 2004 issue of the Journal of the American College of Nutrition.
Another study reported in the November 2007 issue of Mayo Clinic Health Letter highlighted a German study that found eating a small amount of dark chocolate every day reduces the top (systolic) blood pressure number by almost 3 millimeters of mercury (mm Hg) and the bottom (diastolic) blood pressure number by about 2 mm Hg. This study was published in the July 4, 2007, issue of the Journal of the American Medical Association.
On the Flipside of Flavonoid Research
In online Eurek Alert news release, March 5, 2007, flavonoids actually have little or no value in that role, according to an analysis by scientists in the Linus Pauling Institute at Oregon State University.
However, these same compounds may indeed benefit human health, but for different reasons -- the body sees them as foreign compounds, researchers say, and through different mechanisms, they could play a role in preventing cancer or heart disease.
Based on this new view of how flavonoids work, a relatively modest intake of them – the amount you might find in a healthy diet with five to nine servings of fruits and vegetables – is sufficient. Large doses taken via dietary supplements might do no additional good.
A research survey, and updated analysis of how flavonoids work and function in the human body, were recently published in Free Radical Biology and Medicine, a professional journal.
"What we now know is that flavonoids are highly metabolized, which alters their chemical structure and diminishes their ability to function as an antioxidant," said Balz Frei, professor and director of the Linus Pauling Institute. "The body sees them as foreign compounds and modifies them for rapid excretion in the urine and bile."
The large increase in total antioxidant capacity of blood observed after the consumption of flavonoid-rich foods is not caused by the flavonoids themselves, Frei said, but most likely is the result of increased uric acid levels.
Why Dark Chocolate is Different
Chocolate is plant-derived and it is a better source of flavonoids than other foods. Chocolate comes from the cacao (or cocoa) bean. The darker the chocolate, the higher it's likely to be in flavonoids. Not all chocolate is equal when it comes to flavonoid content. Dark chocolate contains a lot more cocoa than other forms of chocolate.
Maybe its true - a piece of dark chocolate a day might keep the doctor at bay.
