Good News About Chocolate
Silvina B. Lotito, Ph.D.
are naturally occurring compounds that are widely distributed in the plant
kingdom, appearing in fruits, vegetables, and plant-derived beverages, such
as tea and wine. Flavonoids play an important role in plants, mainly protecting
them against external pathogens, ultra-violet light, or heat. The main classes
of flavonoids include anthocyanidins, flavones, flavanones, flavonols and
flavanols (also known as catechins). Flavonoids are responsible for the
red, purple, and blue color of fruits and flowers, and play a role in pollination
by attracting insects. They are considered to be the main active component
of some medicinal plants due to their well-documented anti-inflammatory
properties and their activity as modulators of the immune system, among
many other physiological effects. Flavonoids have been claimed to be powerful
antioxidants in a number of different biological systems, protecting against
damage by free radicals. Most of the flavonoids belong to a group of chemicals
called polyphenols, and the antioxidant properties of flavonoids are probably
related to their polyphenolic chemical structure.
It is well accepted that a regular intake of fruits and vegetables helps to prevent a number of chronic diseases, especially cancer and cardiovascular diseases. Heart disease and stroke are known to be consequences of atherosclerosis. The oxidative modification of low-density lipoproteins (LDL, the so-called "bad cholesterol") is believed to play a critical role in the development of atherosclerosis. Oxidized LDL activates endothelial cells in blood vessels to produce certain adhesion molecules that lead to the accumulation of white blood cells in the vessel wall. These modified LDL particles are not cleared from the circulation as they should be, but instead migrate to the subendothelial space where they producing so-called "foam cells", filled with LDL, in the vessel wall. This is the initial step in a series of inflammatory events that finally leads to the formation of atherosclerotic plaques. Presumably, this process would be inhibited if the oxidation of LDL could be prevented.
Dietary antioxidants, especially vitamin C, vitamin E, and lipoic acid, and metal chelators have been shown to prevent LDL oxidation and endothelial cell dysfunction. Previous work at the Linus Pauling Institute and in collaboration with investigators at Boston University School of Medicine has demonstrated that vitamin C inhibits LDL oxidation, substantially improves endothelial function and vasodilation in patients with heart disease, and lowers blood pressure in moderately hypertensive patients. Some metal chelators and lipoic acid, but not vitamin C, can inhibit the activity of adhesion molecules on endothelial cells. Therefore, certain antioxidants could lead the way to new strategies to prevent and treat heart disease and stroke.
Many epidemiological studies suggest that flavonoids have some beneficial role in human health. The high flavonoid content of red wine may, in part, account for the compatibility of a high-fat diet with a low incidence of heart disease mortality in some populations that drink wine regularly, a phenomenon called the "French paradox." Cardiovascular benefits of moderate wine consumption have been thought to be due, in part, to the antioxidant and antiplatelet activities of flavonoids and polyphenols. Platelets are substances in blood involved in clotting whose aggregation can cause heart attacks and strokes. Other epidemiological research, such as the Seven Country Study, has found a correlation between high flavonoid content in a diet rich in fruits and vegetables and a lower risk of mortality from coronary heart disease. The Zutphen Study demonstrated that elderly people who drink large amounts of tea, which is a particularly good source of the flavonoids called catechins, have a lower incidence of stroke.
In addition to some fruits, vegetables, and beverages like red wine and tea, chocolate has been identified as a rich source of flavonoids. For a long time, cocoa beans have been recognized as an important source of polyphenols, although these particular polyphenols had not been well characterized or quantified. The medicinal properties of cocoa were well known to the ancient Maya and Azteccivilizations, and cocoa was considered a valuable and are taken up by white blood cells called macrophages, prestigious food of divine origin. Theobroma cacao (the scientific name of the cocoa plant, meaning "food of gods"), prepared as a chocolate beverage, was used to treat a large variety of problems, including gastrointestinal and liver disorders, angina and heart pain, kidney complaints,infection, and inflammation. Aphrodisiac properties and longevity were also attributed to chocolate by the ancient civilizations.
Cocoa powder and cocoa-derived products, especially dark chocolate, are good sources of flavonoids, mainly epicatechin and its oligomers, called procyanidins. Dark chocolate has the highest total catechin and procyanidin content. The particular procyanidins present in chocolate and related products are not commonly found in such abundance in other plant foods or beverages. Besides their contribution to flavor, procyanidins strongly correlate with the antioxidant activity of chocolate observed in vitro. The latest research suggests that cocoa flavonoids may decrease the oxidation of human plasma compounds (LDL, lipids in general, and physiological plasma antioxidants like vitamin E), modulate platelet activation (an aspirin-like effect), and may positively affect the balance of certain substances involved in hemostatic and inflammatory processes. All these effects of cocoa flavonoids are considered highly relevant to the possible inhibition of atherosclerosis in humans who regularly consume cocoa products.
One important question about chocolate catechins is whether they are effectively absorbed in the body after consuming chocolate. If they are absorbed, then we need to determine the implications that catechin levels in the blood may have for human health. Research carried out at the University of California, Davis, has made important contributions to elucidate these issues. Lucky volunteers were fed different amounts of dark chocolate. Blood samples were obtained from the subjects before chocolate consumption and after two and six hours. Subjects who consumed the highest amounts of dark chocolate had the highest levels of epicatechin in their blood plasma. It was also observed that chocolate consumption significantly increased the total antioxidant capacity of blood plasma and decreased oxidative damage to lipids in the blood, suggesting an in vivo antioxidant role for epicatechin.
The accumulated evidence suggests that the regular intake of chocolate may help prevent some chronic diseases. It has been suggested that chocolate can be an important source of catechins for young people, who may prefer chocolate to tea, or in countries where tea is not as widely consumed as chocolate. Since chocolate in products is accompanied by fat and sugar, eating too much may cause health problems in susceptible people, although the type of saturated fat (stearic acid) in chocolate does not seem to adversely affect the blood lipid profile. Milk chocolate, on the other hand, contains milk fat and may have an adverse effect. As is the case with red wine, enjoying chocolate in moderation seems to be the key. The good news is that chocolate is not only a delicious food enjoyed by millions, but is also an appealing source of potentially healthful compounds.
Last updated May, 2002
Honoring a Scientific Giant with Nutritional Research
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