Chocolate and Cocoa Help Heart but Caffeine Dangerous
14-May-2004 2:00 PM EDT
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Newswise — Dark chocolate and older lovers of cocoa rejoice " you are helping your heart and arteries, according to two studies presented at the American Society of Hypertension's Nineteenth Annual Scientific Meeting.
But another study found those needing a caffeine jolt had better switch to decaf to preserve the endothelium " the layer of cells lining blood vessels that control the ability of blood vessels to dilate and prevent clot formation. Poor endothelial function and arterial stiffness are considered cardiovascular risk factors in addition to smoking, hypertension, obesity and high cholesterol.
"This is the first study to investigate whether chocolate has any favorable effects on cardiovascular function in healthy subjects," says Charalambos Vlachopoulos, MD, of the Athens Medical School, Athens, Greece. "We found dark chocolate improves endothelial function and decreases arterial stiffness in healthy young adults."
Dr. Vlachopoulos and his team of researchers randomized 17 healthy young volunteers to eat either 100 grams of a commercially available dark chocolate bar rich in flavonoids or a placebo in a single blind crossover study.
Flavonoids are a group of chemical compounds naturally found in certain fruits, vegetables, teas, wines, nuts, seeds and roots that are antioxidants. Cocoa has been found to have nearly twice the antioxidants of red wine and up to three times those found in green tea.
"During the chocolate session, artery stiffness decreased and endothelial function improved, but on the placebo day no favorable effects were observed," Dr. Vlachopoulos said. "The favorable effects of dark chocolate lasted for at least three hours."
He said the findings have several important implications. The heart has difficulty pumping when peripheral arteries are stiff. Stiff arteries can lead to isolated systolic hypertension, which mainly affects the elderly. Impaired endothelial function, he said, can also lead to atherosclerosis.
"Dark chocolate, by improving endothelial function and arterial stiffness, emerges as a promising food, high in nutritional value beyond its pleasant taste," Dr. Vlachopoulos concluded. "At this time, we do not know whether the regular intake of dark chocolate or other cocoa beverages could result in a reduction of total cardiovascular morbidity and mortality. Until that time, people should regard the chocolate they enjoy not as a magic beverage like the Aztecs did, but rather as a food which perhaps promotes their cardiovascular health."
According to Naomi Fisher, MD, Brigham and Women's Hospital, Boston, this was the first study examining the effects of naturally occurring flavanol-rich foods and beverages for endothelial dysfunction of aging.
"Our study raises the prospect of ingesting a naturally-occurring substance to reverse that decline," she noted. "It is a follow-up to our earlier randomized study in healthy people that showed cocoa has favorable vascular effects."
Dr. Fisher and colleagues hypothesized that responsiveness to flavonoids via activation of nitric oxide synthase, increases with advancing age. They measured pulse wave amplitude in 27 healthy people, ranging in age from 18 to 72.
Pulse wave amplitude of the 13 people over age 50 rose significantly after drinking cocoa, while the 14 people in the under age 50 group experienced a smaller rise after they drank cocoa.
"Aging is almost universally accompanied by a decline in endothelial function," Dr. Fisher concluded. "Our results provide a plausible mechanism for the protection flavanol-rich foods induce against endothelial dysfunction and resultant coronary events in the elderly."
"Ours was the first study to investigate whether coffee and caffeine could affect endothelial function of healthy people," says Chris Papamichael, MD, Alexandra University Hospital, Athens. "Coffee and caffeine, its main ingredient, are consumed by at least eight of ten adults in western countries, with a mean per capita consumption of approximately 200 mg a day. However, the medical community has long viewed caffeine with suspicion."
As part of the single blind crossover study, 17 healthy young volunteers drank a copy of regular coffee containing 80 mg of caffeine or a corresponding cup of decaffeinated beverage containing less than 2 mg of caffeine. An index called flow-mediated dilation (FMD) was used to estimate endothelial performance. The higher the FMD value, the better the endothelial function.
"After drinking regular coffee, FMD decreased," Dr. Papamichael noted. "There was no such effect when the test subjects drank decaffeinated coffee. Our results indicate that this effect was directly attributed to caffeine since the quantity of caffeine was the unique difference between the two beverages."
Before switching to decaf, Dr. Papamichael cautioned, more clarification is needed.
"At this time, we do not know whether regular intake of coffee could result in an increase of total cardiovascular morbidity and mortality in specific populations or in healthy people," he said. "We also must answer questions such as who should not drink coffee or should the amount of coffee be limited.
"Until we have the answers, some people, especially those with cardiovascular risk factors such as hypertension, diabetes and high cholesterol should enjoy their coffee with caution," Dr. Papamichael concluded.
The American Society of Hypertension (ASH) is the largest US organization devoted exclusively to hypertension and related cardiovascular diseases. ASH is committed to alerting physicians, allied health professionals and the public about new medical options, facts, research findings and treatment choices designed to reduce the risk of cardiovascular disease.