Chocolate For a Healthy Heart

(Cardiovascular Disease, Heart Disease, Stroke, High Cholesterol, Atherosclerosis, Hypertension)

The heart-protective effects of cocoa are probably its most well documented. Dozens of studies confirm the ability of dark chocolate to protect the heart in a variety of ways, including fighting the previously explained oxidation, and inflammation, improving blood platelet function, decreasing the clotting of blood, and allowing blood vessels to relax and become more pliable, reducing blood pressure.

For instance, a team of scientists from Harvard School of Public Health reviewed 136 studies completed on the relationship of chocolate and cocoa to cardiovascular health. The review included all types of research from lab tests to human studies. The research team concluded that chocolate is a major source of flavonoids, (epicatechins, catechins, and procyanidins) and found that the principal fat in chocolate (stearic acid) did not have adverse effects on blood vessels, cholesterol levels or overall CV health because it is metabolized differently than other saturated fats.

The review confirmed the findings of many studies suggesting that regular chocolate intake has potentially beneficial effects. These include lower blood pressure, decreased inflammation in blood vessels, decreased blood clotting, increased levels of high-density lipids (HDL-C-the good cholesterol) and decreased oxidation of low-density lipids (LDL-C), improved endothelial function(increased nitric oxide production), inhibition of leukotriene activity (which causes the constriction of blood vessels and contribute to chronic inflammation), and increase activity of prostacyclins, which help blood vessels “relax” and reduce blood platelets from forming clots.

The authors concluded that regular consumption of chocolate should decrease the risk of cardiovascular-related conditions, and recommended long-term studies to confirm this.

Another study from a joint team of researchers from the University or California-Davis and the University of Dusseldorf in Germany ascertained that the compound epicatechin found in cocoa is directly linked to improved circulation and other hallmarks of cardiovascular function. Say the researchers, "The results of the study provide direct proof that epicatechin is, at least in part, responsible for the beneficial vascular effects observed after the consumption of certain flavanol-rich cocoa [foods]." The researchers explained that that relaxation response observed in the blood vessels or the subjects was mediated by nitric oxide (NO), a key signal released by the inner lining of blood vessels (the endothelium). Because the vessels are able to relax and become less stiff, they are less susceptible to clotting, blockage and risk of high blood pressure.

Key to the study was volunteers from the Kuna Indians, who live in Panama. High blood pressure and other signs of cardiovascular disease are rare among the island-dwelling Kuna, who are also known to consume large amounts of cocoa (about three to four cups a day). However, previous studies have shown that Kuna who have migrated to the city, and consequently consume less cocoa, do not enjoy the same level of cardiovascular health. When they returned to consuming the cocoa beverage they enjoyed improvements in their cardiovascular health.

A recent study published in Archives of Internal Medicine presented new data on cocoa intake and heart disease from older men. The Dutch research team followed 470 men, aged 65-84, who were free of chronic illness, for over 15 years. Food histories were taken and subjects divided into 3 groups by daily cocoa intake: none, low or high. The high cocoa intake was the equivalent of eating about 10 grams of a standard dark chocolate bar per day.

The results were very promising, with the high cocoa group demonstrating slightly lower blood pressure and a 45-50% lower rate of death from cardiovascular disease. This benefit remained even after correcting for the fact that this group was somewhat healthier in general. Interestingly, the men who ate more chocolate also consumed more calories, but were slightly less obese than those who ate no chocolate.

Because the difference in blood pressure was small, the researchers concluded that the decrease in risk of cardiovascular disease must also be explained by other benefits of cocoa, such as improvements in the function of blood vessels, lower blood-glucose levels, lower platelet function, improved cholesterol levels, decreased oxidation of blood lipids, and reduced activity of inflammatory components such as cytokines. The study authors conclude that this long-term review supports the findings of other short-term studies suggesting that cocoa consumption can improve cardiovascular health and lower the risk of cardiovascular disease.

Another study, published in a 2005 issue of the American journal of Clinical Nutrition, found that the proanthocyanin and flavanol content of cocoa again demonstrated significant antioxidant properties and the ability to protect the heart and vascular system. "These nutrients have been shown to affect numerous intracellular signaling cascades, and to influence the cardiovascular system by enhancing vascular function and decreasing platelet activity." The researchers continued by stating that cocoa and chocolate containing foods may "be associated with reduced risk for vascular disease."

Researchers from the University of California, San Francisco, and Tufts University discovered that the epicatechin content of dark chocolate is likely responsible for the improved dilation (relaxation) of blood vessels by enhancing the function of the blood vessel's endothelial lining. It's also important to note that the patients' blood levels of lipids did not increase during the trial. Additional review of research, which was compiled by some of the same researchers, suggests that flavonoids from chocolate have an anti-inflammatory effect by controlling the activation of several pro-inflammatory agents in the body.

Another recent study from Harvard scientists investigated the potential benefits of cocoa on the vasodilation (relaxing and opening up) of blood vessels. The researchers found that a flavanol-rich cocoa beverage enhanced several measures of blood vessel function among both old and young subjects, but especially among the older subjects. The research team concluded that those individuals with greater endothelial dysfunction (such as the older population) may experience greater benefit by consuming flavanol-rich cocoa products.

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Japanese Research Solidifies Cocoa's Heart-Friendly Benefits

Japanese scientists recently conducted a double-blind clinical trial involving 160 subjects to assess the cardio-friendly effects of cocoa. One group of people ingested a low-flavanol cocoa drink for 4 weeks (the control group), and another group ingested a high-flavanol cocoa drink.

After 4 weeks, the high-flavanol group experienced significant improve-ments. The researchers found that the blood levels of LDL cho!estero! (the “bad” cholesterol) and oxidized LDL cholesterol (the most dangerous form of LDL to the heart and blood vessels) were lower in the high-flavanol group. They also found that levels of HDL cholesterol (the "good" cholesterol) were raised compared to the control group. The findings were published in a 2007 issue of the Journal of Nutrition.

Another study from some of the same research team, published in the American Journal of Clinical Nutrition, assessed the effects of cocoa polyphenols on two groups. One group received a placebo (sugar drink), and the other received the sugar drink and 26 grams of a cocoa powder daily for 12 weeks. The results were similar to the previous study. In the cocoa group, HDL levels were significantly increased while LDL levels were lowered and LDL oxidation was lessened. Again, these findings support the results of dozens of other studies indicating that regular cocoa consumption can indeed lessen the risk factors for cardiovascular disease.

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One more reason cocoa has displayed a cardio-protective influence may be its effect on prostacyclins, according to Dr. Carl Keen, from the University of California-Davis, who has studied the bioactivity of chocolate and its components very thoroughly. Prostacyclins are naturally occurring compounds that inhibit platelet clotting, reduce the risk of thrombosis and blood vessel constriction, and prevent the oxidation of LDLs (the "bad" cholesterol), as well as its entry into the blood vessel walls, where it can result in inflammation. Prostacyclins also lower the activity of cytokines, agents that contribute to unwanted, chronic inflammation. Prostacyclins also activate the production of nitric oxide in the endothelial tissue, which allows blood vessels to expand and become more flexible. Prostacyclins also appear to inhibit the activity of lipooxygenase, an enzyme that plays a pivotal role in the inflammation process - it converts omega-6 arachidonic acid to the inflammatory molecule leukotrienes. Stopping this inflammatory response again reduces the blood vessel damage.

Sies, et al, outlined a proposed model for the development of heart disease and diabetes based on postprandial stress (after-meal stress). They felt that most people in Western society are in a post-prandial state most of the day. If a meal is high in fats and refined sugars without the benefit of antioxidants, we are very prone to the development of the heart disease, hardening of the arteries, and diabetes. The vessel walls are very impaired during this post-prandial state as are the abilities to metabolize sugars appropriately. The addition of anti-oxidants to the diet stops this process and improves the health of blood vessel walls by preventing LDL cholesterol from causing damage.

Chocolate and cocoa flavonoids have been found in several studies to stop platelets from clotting, preventing heart attacks and strokes (cardiovascular accidents). A recent study found that cocoa contains N-caffeoyldopamine and N-coumaroyldopamine, both of which play an important role in suppressing the mechanism whereby blood platelets stick to blood vessel walls. They suppress the adhesive molecule called P-selectin, which "glues" platelets to white blood cells and blood vessel walls.

Scientists suggest there may be other reasons for cocoa's heart-friendly effects. Two studies found that cocoa was able to inhibit the activation of blood platelets and cells (leukocytes) that contribute to inflammation. A review of the data also suggests that constituents of the cocoa other than flavanols are likely responsible (at least in part) for the benefits.

It's quite evident that, although we may need more research to learn more about how the polyphenol compounds in cocoa work within the body, chocolate represents a promising weapon in the fight against the various forms of cardiovascular disease.

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Science Spotlight: Cocoa Flavonoids & Blood Circulation

In a 2009 trial published in the International Journal of Cardiology, Japanese researchers investigated the effects of cocoa flavonoids on blood flow. In the study, 39 participants ingested either a flavonoid-rich cocoa or a white chocolate low in flavonoids for 2 weeks.

Flavonoid-rich dark chocolate intake significantly improved coronary circulation in healthy adults, independent of changes in oxidative stress parameters, blood pressure and lipid profile, whereas non-flavonoid white chocolate had no such effects.

Additional findings from researchers at Yale University indicate that individuals consuming a flavonoids-rich chocolate bar experienced significant improvement in endothelial function and blood pressure in overweight adults. Endothelial cells are those that help blood vessels dilate, thereby decreasing blood pressure and minimizing risk of other cardiovascular conditions.

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How Does Heart Disease Begin?

Cardiovascular disease is the #1 killer of American men and women. It has become such a big problems that some experts estimate that there will not be enough cardiovascular surgeons to handle all the bypass surgery needs in the near future.

Why does heart disease occur? We all start out with very clean heart blood vessels, which bring nutrients to the heart muscles. Various risk factors, including age, gender, smoking, inactivity, obesity, cholesterol, low blood pressure, diabetes, and oxidative stress, eventually contribute to the onset of any of several forms of cardiovascular disease.

These risk factors also increase the occurrence of inflammation in our blood vessels, which makes the vessels susceptible to particles of "bad" cholesterol, or LDL cholesterol (LDL-C),Rowing in our vascular system. The LDL-C particles are ingested by macrophages, whose role is to eliminate pathogens, toxins and other dangerous cells. However, due to long-lasting exposure to these particles, the macrophages begin to swell up, turning into fat-laden foam cells. Foam cells enmesh themselves into the connective tissue and smooth muscle cells in the blood vessels.

This process draws helper cells (T cells) to fight the disease, but they end up causing more inflammation and suddenly there is a continuous cycle of fat being incorporated into the blood vessel wall.

At first the damage is minor and is in the form of fatty streaks or plaques; but as the body tries to cope with the disease, it begins to place a fibrous covering over the streaks resulting in hardening of the arteries. The plaques can increase in size to the point of stopping blood flow.In many cases the plaques rupture and platelets gather on the ruptured plaques forming blood clots (thrombus). These clots can either block the blood flow causing a heart attack or break off and travel to the brain or lungs, causing a stroke or pulmonary embolism. This vicious cycle involving oxidation and inflammation can result in severe cardio-vascular disease. Elevated blood sugars can also accelerate this process.

Hardening of the arteries causes further damage throughout the body. When a healthy heart pumps blood through the circulatory system, the vessels flex and reduce the pressure by the time the blood reaches organs and the capillaries. Think of a thin rubber tube, as fluid is forced in the tube expands and the fluid coming out of the rubber tube is less than going in. If the tube is transformed into a metal rigid pipe, the pressure coming out of the pipe is the same as going into it. This same process occurs with hardening of the arteries (arteriosclerosis or athero-sclerosis).The blood pressure becomes elevated throughout the body, resulting in damage to organs and small blood vessels. In addition, as the blood returns to the heart at a high pressure it starts to dilate the heart muscles over time, resulting in an enlarged heart (cardiomegaly). The end result is congestive heart failure with fluid retention in the lungs, liver and lower legs. The heart gets bogged down and cannot pump blood efficiently, resulting in decreased ability to function, usually resulting in death. The hardening of the arteries occurs in the brain manifesting itself as dementia, in the kidney as renal failure, in the eyes as blindness, and in the skin as ulcers. This is a very complex process but it all starts out with the above-listed risk factors of oxidation and inflammation.

Dark Chocolate Protects Blood Vessels, Endothelial Function

One recent study shed light on exactly how chocolate and its key ingredients may protect the cardiovascular system. It's known that particles of low-density lipids (LDL) are able to occupy receptor sites located on the lining of the blood vessels (called the endothelium). These particles eventually become oxidized, which triggers an inflammatory response that, if occurring over a long period of time, contributes to the dysfunction of the endothelium and a variety of other conditions lumped under the umbrella term cardiovascular disease.

The study, led by famed sisters Mary and Marguerite Engler, sought to determine what effects flavonoids from cocoa might have on the function and health of the blood vessels. In the study, 21 subjects were given either high-flavonoid dark chocolate bars or low-flavonoid chocolate bars every day. After 2 weeks, the subjects were tested for changes in their endothelial function, their blood pressure, blood-lipid profile, and blood epicatechin concentrations.

The results showed that the endothelial function of those eating the high- flavonoid chocolate was significantly higher than those eating the low-lavonoid chocolate. In addition, the blood - epicatechin concentrations of the high-flavonoid group were also significantly higher than the low-flavonoid group. These results led the researchers to state that consumption of flavonoid-rich dark chocolate improves the function and health of the blood vessel wall (endothelium), which plays a pivotal role in the overall health of the heart and cardiovascular system, and may provide other cardio-protective benefits because of the increased catechin concentrations.

Another review conducted by the Engler sisters supported these findings. In the review, they suggest that possible benefits of consumption of cocoa flavonoids include lower blood pressure, improved endothelial function, decreased blood clotting, normalizing of immune function and inflammatory state, optimizing of nitric oxide production, and increased anti-oxidant activity.

They suggest that regular consumption of flavonoids can prevent the oxidative stress brought about by the various common risk factors (many lifestyle related), which leads to endothelial dysfunction, which directly precedes the formation of arterial plaque, blood clots, athero-sclerosis, thrombosis and eventually heart attack and stroke.

Other recent findings support the research done by the Englers. A study published in the Journal of Cardiovascular Pharmacology by a German research team investigated the possible benefits of cocoa flavanols on the endothelial function of blood vessels. The scientists found that after 1 week of drinking a high-flavanol cocoa beverage, individuals who smoked (and therefore suffered from substantial endothelial dysfunction) experienced substantial improvement in the dilation of blood vessels and blood flow, as well as improvement in blood nitrite and nitrate levels, both used to measure endothelial dysfunction.

And a study from a University of California-Davis team of scientists found that cocoa consumption improved endothelial function, and decreased the adhesion ("sticking") of vascular cell molecules in post-menopausal women who suffered from high cholesterol levels. Wang-Polagruto JF, et al. Chronic consumption of Flavanol-rich cocoa improves endothelial function and decreases vascular cell adhesion molecule in hypercholesterolemic post-menopausal women.

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Why is Nitric Oxide (NO) So Important?

Numerous studies confirm the fact that damage to the lining, or endothelium, of the blood vessel walls, is a major factor in the progression of cardiovascular disease and eventually heart attack, stroke and other coronary events. Key to health of the endothelium is nitric oxide (NO). Nitric oxide has risen to take the status of chemical "superstar" in recent years. In fact, American researchers won the Nobel Prize in 1998 for their work involving NO.

We know that nitric oxide is crucial to the health of the endothelium and cardiovascular system in general because it does the following:

• It allows blood vessels to dilate, or become more "relaxed."This means that the blood vessel can expand when necessary, thereby reducing the risk of a number of health conditions.
• It reduces the clotting action of red blood platelets, which decreases risk of stroke and related conditions.
• It inhibits the production of smooth muscle cells in the vascular system and smooth muscle contractions.
• It stops oxidation of LDL cholesterol.
• It stops the expression or action of the cell adhesion molecules.
• It reduces oxidative stress in the vascular system by inactivating superoxide anion, a potent free radical.
• It slows the recruitment of the pro-inflammatory leukocytes to a particular area.

 

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Summary Points

• Cardiovascular disease is the #1 killer in the United States.
• Fortunately, dozens of studies demonstrate that dark, healthy chocolate) can substantially improve cardiovascular health and protect against disease.
• Studies show chocolate's abilities to decrease inflammation, relax blood vessels, neutralize free radical damage, improve the ratio of fats (including cholesterol) in the blood, improve communication between cells, enhance nitric oxide production, decrease blood clotting, improve blood pressure, and enhance blood flow and blood vessel performance in the brain.
• Studies among the Kuna Indians are just a few of many showing the tremendous cardiovascular benefits regular chocolate consumption can have.
• Cocoa's polyphenols seem to be the primary components responsible for its heart and blood vessel friendly capabilities.