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Dark Chocolate: The key to cardiovascular health?

Allison Hartog

 

 

October 23, 2007

 

Introduction:

            In recent attempts to assuage our guilt as an ever-growing (in the literal sense) population of sedentary and obese individuals, much research has been conducted into the health benefits of foods popularly viewed as “saboteurs” of various weight loss efforts.  Chocolate is a food that many people engage in a love/hate relationship with. Its popularity as an aphrodisiac is well-known and it is a delicious ingredient in nearly every dessert choice we may face.  It is a source of comfort in stressful times as the sinfully sweet goodness melts in your mouth in the form of rich dark chocolate cake, a bowl of chocolate ice cream, or a pan of fresh baked, ooey-gooey, warm brownies.  After its consumption, however, it often can be the cause of immense guilt.  Well-known to be loaded with saturated fats and calories, the psychological anguish is tantamount to the physical damages one can incur from indulging too often. 

           

            But recent claims seem to indicate that there may yet be hope for all the suffering “chocoholics” that just can’t seem to get enough of the delectable dessert. It has been proposed that dark chocolate may produce the same cardiovascular health benefits previously ascribed only to sickeningly “good-for-you” staples such as blueberries, various veggies, and recently, wine and green tea. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chocolate is a heart healthy food?

 

 

            Researchers today aren’t the first to claim cardiovascular benefits can be produced by chocolate consumption. In the 17th century, chocolate was popularly thought to strengthen the heart and was used to treat heart problems. (Steinberg et al, 2003) Today, that claim is being made again by companies and researchers alike.  Of course – for the sake of our consciences – we are biased to believe that chocolate really does have miracle ingredients that contribute to cardiovascular health, but how accurate are the claims? 

 

 

A Clever Marketing Campaign:

 

            The belief that dark chocolate actually has health benefits has led to the development of companies that cater specifically to a population trying to lead a healthy lifestyle without giving up the occasional indulgence in their favorite sweets.  CocoaVia is one such brand. http://www.cocoavia.com/story/  Cocoa Via Brand Heart Healthy Snacks are so confident in the health benefits of dark chocolate, that they include the claim in their name.  CocoaVia guarantees that their snacks have 100 mg of naturally occurring cocoa flavonols, “like those found in red wine in green tea.”  Dark chocolate supposedly helps blood flow by allowing blood vessel walls to relax and promotes healthy platelet activity which aids in maintenance of healthy circulation and blood vessels.  The benefits don’t end there though! Vascular health is promoted by decreasing the oxidation of LDL cholesterol (that’s the bad kind) which is believed to decrease the likelihood of formation of plaque in the arteries.  So how accurate are these claims about the protective powers of dark chocolate?

            The Xocai company also touts the benefits of “healthy chocolate.”  This company claims that chocolate consumption increases energy levels and provides “a sense of overall health and wellbeing like never before.”  Their main appeal is to the rejection of popular “restrictive dieting” methods that frustrate many dieters. This company combines chocolate with other ingredients, such as Acai, that also are thought to have health benefits.  http://www.whyxocai.com/product.html

            It almost sounds too good to be true. Chocolate is a heart healthy part of your diet? Comparable to apples, blueberries, cheerios, and other antioxidant rich foods? 

 

What the Science says:

 

            Science has quite a bit to say on the cardiovascular benefits of dark chocolate.  Steinberg and colleagues drew upon the research of 123 studies on the subject in their 2003 paper, Cocoa and chocolate flavonoids: Implications for Cardiovascular Health. Dark chocolate derived from the plant Theobroma cacao is thought to provide its health benefits with its high antioxidant content.  Dark chocolate, if processed correctly, retains more of the natural cacao bean than other types, such as milk chocolate.  This makes dark chocolate a rich source of flavonoids, specifically the flavonoids catechin, epicatechin, and procyanidins. 

 

 

 

 

 

 

Flavonoids – what are they and what do they have to do with cardiovascular health?

 

            Flavonoids can be found in fruits, veggies, wine, tea and cacao (to name a few sources).  Their chemical structure indicates that flavonoids have antioxidant capacity which makes them capable of scavenging harmful free radicals in our blood stream.  Flavonoids are extremely beneficial to cardiovascular health.  They help to keep cholesterol from gathering in the blood vessels, inhibit the immune responses that may lead to clogged arteries, and reduce platelet reactivity which reduces the risk of blood clots.  Once flavonoid containing foods are consumed, they are acted upon by enzymes and show up as different metabolites in the blood stream. One such metabolite that is rapidly absorbed by humans is Epicatechin. The concentration of epicatechin in the blood can be used to determine the amount of flavonoids that were consumed and then predict the potential health benefits based on that knowledge. Ideally, a food will produce a high concentration of these metabolites if it contains flavonoids that could increase cardiovascular health.  It has been found that the concentration of epicatechin from dark chocolate is in the same range produced by consuming onions, apples, and tea. Sounds pretty good! So if flavonoids are found in dark chocolate, why not grab some dark chocolate instead of an apple next time you’re hungry?  Read on…

 

 

 

 

 

The Evidence Grows

           

            A more recent study on the cardiovascular health benefits of dark chocolate was conducted in 2004 by Mary Engler and her colleagues at the University of California, San Francisco.  This study wanted to test previous studies’ results that indicated that cacao flavonoids had antioxidant properties and inhibited platelet activity, both of which have positive effects on overall cardiovascular health. 

 

            Subjects and Procedure –

           

            This study used 22 volunteers between the ages of 21 and 55 who were deemed in good health at the beginning of the study.  The study was randomized, double-blind (meaning both the subjects and researchers were unaware which group, control or experimental, they were in) and took place in a two-week time period.  The subjects either were instructed eat a piece of high-flavonoid or low flavonoid dark chocolate daily.  Other instructions were to maintain their usual level of physical activity, keep a food diary, and refrain from flavonoid-rich foods and beverages on a provided list.

 

            Results –

                                                                                               

                  The subjects that were given the high-flavonoid dark chocolate were found to have a significant increase in the concentration of plasma epicatechin compared to the subjects in the low-flavonoid group, which, as discussed before, indicates increased benefits for the cardiovascular system in the form of better blood flow in the arteries which is good for your heart.  This study also found that increased epicatechin concentration levels are associated with improved endothelium-dependent vasodilation, which is a fancy way of saying that blood vessels dilate and relax in a healthy way.  Stiffness of blood vessels can lead to diseased blood vessels, so the ability to relax is key to maintaining cardiovascular health.  Ingesting dark chocolate rich in flavonoids produces important protective benefits for the cardiovascular system.

 

 

 

 

 

 

 

 

 

And Grows…

 

            Many studies have been done investigating the potential cardiovascular benefits of cocoa and we only look at a few of them in-depth here.  Two more worth mentioning further strengthen the claim that there are indeed health benefits to be gained from indulging in a diet that includes cocoa. 

 

            The first study, conducted by Taubert, Roesen, Lehmann, Jung, and Schomig in 2007 had a set-up similar to that of Engler’s study that was just outlined. Participants received either flavonoid rich dark chocolate or a comparable amount of white chocolate lacking the flavonoids believed to be beneficial.  However, the participants in this study all had upper-range prehypertension or stage 1 hypertension and were currently untreated for this. The researchers wanted to test the effects of dark chocolate on the blood pressure of the participants.  The participants ate the chocolate for 18 weeks and then their baseline blood pressure at the start of the study was compared with their end blood pressure after the 18 weeks.  Their results again confirm what the previous studies have found: dark chocolate intake reduced both systolic and diastolic blood pressure in participants assigned to that group and Hypertension prevalence declined from 86% down to 68%. White chocolate, however, caused no changes in blood pressure.

 

            Another interesting study worth mentioning is a long-term observational study that examined the relationship between cocoa intake and blood pressure but then also did follow ups to see if cocoa intake was prospectively related to cardiovascular mortality. The Zutphen Elderly Study is different from the short-term intervention studies we have discussed. It is an observational study – meaning that no one’s diets were manipulated, merely observed over time to see if there was a relationship between the amount of cocoa one consumed and their health.  Data was collected from 470 elderly men.  First, relationship between cocoa and blood pressure was analyzed cross-sectionally using baseline blood pressure and blood pressure after five years and comparing this to their estimated cocoa intake as assessed by checking their self-reported dietary history.  It was found that average systolic and diastolic blood pressure was lower among the men consuming the most cocoa. This implies, once again, a correlation between cocoa consumption and lower blood pressure.

            In order to determine if cocoa could be a protective factor against cardiovascular mortality, a prospective analysis was done.  Overall, 314 men in the study died, 152 of cardiovascular disease.  Assessing these individuals’ food records from the 15 years they were in the study could determine if indeed their cocoa intake had been lower than those who were still living or those who died of other causes. It was found that cocoa intake is inversely associated with cardiovascular mortality.  Regular cocoa intake was found to lower risk of cardiovascular and all-cause death by 45%-50%. 

            However, many limitations exist in an observational study that need to be pointed out. There is a strong possibility of confounding variables – chocolate intake could be related to another variable that could be the real cause of lower blood pressure or cardiovascular mortality. Possible confounds might be physical activity and dietary factors.  The study also may be limited in its generalizability since all participants were elderly males.  Even though this study has its limitations, it can be strengthened by further observational and experimental studies and therefore is valuable because it points us in a direction for future research in this area.  It seems to indicate that long-term daily intake of small amounts of cocoa may lower blood pressure and decrease risk of cardiovascular mortality.

 

Helps not only the healthy…

 

            So what if you are an individual already suffering from a cardiovascular disease? With the 2004 stats reporting that 79,400,000 Americans have one or more forms of cardiovascular disease, this is a question many may be asking (Cardiovascular Disease Statistics, AHA).  Never fear! It isn’t too late to turn your health around by also engaging in the dark chocolate trend. Taking a new spin on the dark chocolate question, the American Heart Association recently funded a study that looked at individuals suffering from Hypertension (high blood pressure) and the effects of dark chocolate on their blood pressure, cholesterol levels, and also vasodilation of the blood vessels.

 

            The subjects of the study were 10 men and 10 women with essential hypertension who had never previously been treated for their disease. They first went through a 7-day phase that excluded all cocoa foods.  At the end of this phase, they were randomly assigned to receive either a 100-g dark chocolate bar or a 90-g white chocolate bar for the next 15 days. Both bars had the same amount of calories (480) and similar amounts of cocoa butter, fiber, electrolytes, macronutrients, and vitamins so that the only thing significantly differing between the two was the flavonoid content.  After 15 days, the subjects again went through a 7-day cocoa free phase before being switched so that the group previously consuming the dark chocolate now ate white chocolate and vice versa. They ate their novel chocolate for 15 more days.  Throughout the entire process, they kept food diaries and controlled their weights by substituting the chocolate bars for similar energy-dense foods.

 

            The results are very promising.  Overall, the subjects experienced the most benefits when consuming flavonal-rich dark chocolate. It decreased blood pressure, improved LDL/HDL cholesterol ratios and improved endothelial vasodilation.  Data was collected after each 15-day chocolate phase.  Blood pressure decreased in the dark chocolate subjects, but remained consistently high for those consuming white chocolate.  As for cholesterol, another important component of overall cardiovascular health, total cholesterol levels went down for the dark chocolate group and remained constant for the white chocolate group. What is also interesting to note is that total LDL cholesterol levels (what is commonly referred to as “bad” cholesterol) also decreased in the dark chocolate group and didn’t change for those eating white chocolate. This means that not only did entire cholesterol go down for those eating dark chocolate, but the ratio between their “good” HDL cholesterol and “bad” LDL cholesterol also improved since the HDL cholesterol remained unchanged in either group. Vasodilation was also found to improve allowing more blood flow and contributing to the decreased blood pressure results in those consuming dark chocolate. The same was not found for white chocolate.

 

           

 

 

 

Less is More!

           

            Even though many studies indicate the benefits of flavonoid-rich dark chocolate, not enough research exists to form any sort of dosage that could be recommended by public health providers that would provide maximum benefit to an individual.  The best advice at this time is to consume a variety of flavonoid containing foods, such as fruits, veggies, and beverages as an integral part of a diet that promotes cardiovascular health.  Including dark chocolate in moderate amounts gives dieters increases options for concerned dieters and may aid them in sticking to a diet longer if they feel they are not giving up their favorite sweets.  It must be remembered though that dark chocolate, in addition to its heart healthy flavonoids, is also very energy dense compared to other flavonoid containing foods.  Its high fat and calorie content is certainly a concern for those struggling with cardiovascular disease and should be considered when making dark chocolate a part of your diet. Also- the chocolate used in many of these studies has a much higher flavanol content than many dark chocolates you might pick up from your supermarket. As was mentioned earlier, flavonoids may be lost in the processing of the cacao beans which would make these chocolates incapable of producing the same benefits found in these studies. As chocolate companies become aware of the health benefits produced by careful processing, more and more are taking steps to ensure they can indeed boast that their chocolate is “heart healthy.” 

 

            The best advice to take away from this is that dark chocolate, in moderation, is a very good source of heart healthy flavonoids and can lead to many health benefits. It should be only one source of these flavonoids and part of a very diverse, healthy diet that includes fruits and veggies and a lifestyle that includes regular exercise.  Cardiovascular health is influenced by many factors, only one of which is the amount of dark chocolate you consume!

 

 

 

 

 

 

 

Bibliography:

 

Steinberg, F.M., Bearden, M.M., Keen, C.L. Cocoa and Chocolate flavonoids: Implications for cardiovascular health. Journal of the American Dietetic Association 103: 215-223, 2003.

 

Engler, M.B., et al. Flavonoid-Rich Dark Chocolate Improves Endothelial Function and Increases Plasma Epicatechin Concentrations in Healthy Adults. Journal of the American College of Nutrition 23: 197-204, 2004.

 

Grassi, D., Necozione, S., Lippi, C., Croce, G., Valeri, L., Pasqualetti, P., Desideri, G., Blumberg, J.B., Ferri, C. Cocoa reduces blood pressure and insulin resistance and improves endothelium-dependent vasodilation in hypertensives. Hypertension. 46: 398-405. 2005.

 

Buijsse, B., Feskens, E. J. M., Kok, F.J., Kromhout, D. Cocoa Intake, Blood Pressure, and Cardiovascular Mortality: The Zutpen Elderly Study. Archives Internal Medicine. 166: 411-417. 2006.

 

Taubert, D., Roesen, R., Lehmann, C., Jung, N., Schomig, E. Effects of Low Habitual Intake on Blood Pressure and Bioactive Nitric Oxide. JAMA. 298:49-60. 2007.

 

 

American Heart Association. Cardiovascular Disease Statistics. 9/8/07. http://www.americanheart.org

 

 

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