Nothing quite reveals the depth of love and affection like a gift.
On February 14, 2000, Americans gave the objects of their love and affection more than 35 million heart-shaped boxes of chocolate.
Millions and millions of chocolate hearts.
Are we going to talk about a Valentine’s chocolate heart?
We are going to talk about chocolate being heart healthy. We are going to show you that nature has gifted us all with a wonderful and amazing preventive for our heart and blood vessels. We are going to look at how chocolate can help maintain your cardiovascular health. Like most of the other perceptions about chocolate that we have all grown up with, we are about to shatter another "chocolate is unhealthy myth" by revealing the research that shows that chocolate is good for your heart.
So, lets move right along to the satisfying and stress-free part of this chapter – what chocolate can do for you and your heart!
CHOCOLATE – A HEART HEALTHY FOOD
This is where life starts to get interesting for chocolate lovers. Now that we know a bit more about heart disease and how it happens, we have a very good background for learning about the role that chocolate can play in keeping our hearts healthy. While traditionally chocolate has been lumped in with all those other foods that we have been told are unhealthy and bad for us, and particularly for our hearts, Dr Penny Kris-Etherton and colleagues from the Pennsylvania State University, wrote in 2000 that there was no evidence of any link between eating chocolate and coronary heart disease. So how is it that chocolate is actually good for the heart.
In Chapter Two – I apologise for continually referring back to it, but chocolate is just so chock-full of wonderful nutrients; if you haven’t read it yet, do it now – we found out about all the vitamins, minerals, antioxidants and other compounds that chocolate contains.
It is a great source of magnesium, chromium, iron, copper, calcium and potassium. It is great for folic acid and vitamin E and also contains vitamin A, K and other B group vitamins. Then there are the antioxidants – specifically the flavonoids. And fully one third of the fat is oleic acid, which is the same as the fat in olive oil.
All these nutrients are important for health, and some of them are very important for heart health. So let’s take a stroll through each of these and see just how chocolate can help make yours a healthy heart.
Vitamins and Minerals
Folic acid is probably the most important of the vitamins in chocolate. A two-ounce bar of dark chocolate can offer you 3.5% of your daily requirement of this vital B group vitamin. If American adults were to get enough folic acid it is estimated that 50,000 deaths from cardiovascular disease could be prevented each year. A Finnish study, published in the American Journal of Clinical Nutrition in 2004, investigating ischaemic heart disease risk factors found "that moderate-to-high serum folate concentrations are associated with a greatly reduced incidence of acute coronary events."
Studies have shown that folic acid regulates the body's production and use of homocysteine, an amino acid in the blood that attacks blood vessel walls and promotes cardiovascular disease. Scientists believe that that it is a major risk factor in 10 to 40 percent of heart attacks and strokes in the United States.
Normally, homocysteine doesn’t linger long in the blood stream. It is broken down by the B group vitamins, particularly folic acid. If you aren’t getting enough, your homocysteine levels rise and put your arteries at risk of damage. Dr David Wald, a cardiologist in the United Kingdom, and his colleagues found that lowering homocysteine concentrations by increasing folic acid intake would reduce the risk, on average, of ischaemic heart disease by 16%, deep vein thrombosis by 25% and stroke by 24%.
In addition, a study published in Circulation in 1999 showed that folic acid improved the ability of blood vessels to dilate, improving blood pressure. These findings have since been confirmed in other studies.
Vitamin E is a powerful antioxidant and it helps to protect call membranes from free radical damage. It is a fat soluble vitamin comprising four different forms of tocopherol as well as tocotrienols. Alpha tocopherol is probably the best known and it is the most common form found in vitamin E supplements.
Although there has been quite a lot of medical research that suggests that vitamin E is useful for reducing the risk of heart disease, largely through limiting the oxidation of low density lipoprotein, it is actually the gamma-tocopherol form of vitamin E that we are most interested in. It is the gamma tocopherol that is prevalent in chocolate, and it protects against nitrogen-based free radicals. As a result, gamma-tocopherol may play an important role in protecting against diseases associated with chronic inflammation, including heart disease.
Dr Maret G. Traber, Professor of Nutrition at the Linus Pauling Institute, says "Gamma-tocopherol concentrations in the blood have been reported to be significantly lower in coronary heart disease patients compared to healthy subjects, suggesting that the low Gamma-tocopherol concentrations increased the risk of coronary heart disease."
Several studies have shown that levels of gamma-tocopherol are inversely related to the risk of coronary heart disease – in other words the lower your levels of gamma-tocopherol the greater your risk of heart disease. In a paper published in the Journal of Internal Medicine in 1996, Researchers from the University of Uppsala in Sweden say that, in a group of 207 men, 69 of whom had coronary heart disease, gamma-tocopherol levels were significantly lower in the men who had heart disease than in the healthy men. Interestingly the alpha-tocopherol levels did not differ markedly between the two groups suggesting that alpha-tocopherol is not the important form of vitamin E.
This research was confirmed by German scientists in 1999 who concluded that gamma-tocopherol levels were significantly lower in coronary heart disease patients compared to healthy subjects.
So this form of vitamin E which is particularly prevalent in chocolate and cocoa, and that is hard to get in supplement form, is just one more way to reduce you risk of dying from heart disease.
As exciting as the benefits of both folic acid and gamma-tocopherol, is the link between chromium and heart disease. Chocolate is one of the best dietary sources of this essential nutrient. Most other dietary sources are so processed and refined that the chromium is refined right of them.
Dr Richard Anderson, of the Beltsville Human Nutrition Research Center, says that chromium is an essential element required for normal carbohydrate and lipid metabolism, that insufficient dietary chromium has been linked to maturity-onset diabetes and cardiovascular diseases, and that the dietary chromium intake of most individuals is considerably less than the suggested safe and adequate intake.
In a study published in the journal Metabolism in 1992, Israeli scientists reported that supplementation with chromium and subsequent increases of chromium levels in the blood reduced the level of triglycerides and increased the level of the high density lipoproteins (the good cholesterol) in the study subjects.
It is believed that chromium increases insulin sensitivity which can modify the risk of both diabetes and cardiovascular disease (CVD). Publishing the results of a study on diabetic men with cardiovascular disease in Diabetes Care in September 2004, researchers from the Harvard School of Public Health said that that diabetic men with CVD have lower levels of chromium than healthy men.
Calcium and Magnesium
Calcium is the most abundant mineral in your body and we all know that calcium is used to build bone. In fact, 99 percent of the calcium in your body is contained in your bones but one percent is used for vital processes such as nerve impulses and muscle contractions – including the contractions that cause your heart to pump blood – and the expansion and contraction of blood vessels.
So, you’re probably starting to think that calcium has a role to play in heart health. Well, you would be right, and we already know that chocolate is a good source of calcium along with its "co-mineral", magnesium.
Magnesium is essential for the conversion of vitamin D to a form that enables the body to absorb and utilize calcium. The highest concentrations of magnesium in the body are in those tissues that are most metabolically active, such as the brain, heart, liver, and kidney. We can see that we need to look at these two minerals together.
Deficiencies in both calcium and magnesium have been associated with high blood pressure and cardiovascular disease.
A number of studies have found that there is significant decrease in systolic blood pressure with calcium supplementation, both for people suffering from high blood pressure and for those without. However, some researchers concluded that the effect was too small to support the use of calcium supplementation for preventing or treating hypertension. But chocolate and cocoa powder are very good dietary sources…
In 1999 Dr David McCarron and Molly Reusser, from Oregon Health Sciences University said that:
"There is no question that the calcium available to the organs that participate in cardiovascular control is integral to blood pressure regulation. Furthermore, it is becoming increasingly clear that dietary calcium is a key factor in this process."
They also refer to the DASH study – the Dietary Approaches to Stop Hypertension – and two meta-analyses of previous research on calcium and high blood pressure, saying:
"The findings from the DASH study and the summary reports of Birkett and Bucher et al., covering in excess of 75 well designed trials, leave little doubt that adults would be prudent to consume adequate dietary calcium to reduce their risk of developing hypertension, the most common cardiovascular disorder in adults."
In addition to the impact on high blood pressure, magnesium deficiency can increase the risk of heart attacks and strokes. In one study, published in 1999, Dr Earl Ford of the Centers for Disease Control and Prevention in Atlanta, found that low levels of magnesium were not only associated with deaths from heart disease. He said that of the 12,340 people in the study "participants with higher serum concentrations [of magnesium] had a 21-34% reduced risk of dying from ischemic heart disease."
In another study published in Circulation, Dr Alberto Ascherio and his colleagues from the Harvard School of Public Health, found that low levels of magnesium in the 43,000 plus men that were studied were associated with all forms of stroke, and the association was strongest in the men who already had high blood pressure.
In Chapter Two we discovered that chocolate is the major sources of dietary copper in the American diet. In fact, a two ounce bar of dark chocolate can provide 20 percent of our daily copper requirements. So, when we find out that copper, too, plays a crucial role in heart health we can see just how important chocolate is to our health and wellbeing.
Copper is involved in many bodily processes including helping to build bones and also making blood – so that is a good start. In terms of cardiovascular disease copper’s role in forming elastin and collagen is more important. These form the connective tissues of muscles, heart and blood vessels, among other things. Copper deficiency leads to weakened hearts and blood vessels and can result in death from heart failure or a ruptured aorta.
In 2000 researchers from the Northern Ireland Centre for Diet and Health wrote in the journal Biological Trace Element Research that a copper deficient diet caused lesions on the aorta, the main artery from the heart, and raised blood cholesterol levels in mice. In a 2004 study researchers were able to modulate the impact of a high cholesterol diet in rabbits by reducing the development of atherosclerosis in the rabbit’s arteries when the diets were supplemented with copper or zinc. Several studies have demonstrated the effect of copper deficiency in human beings, particularly the increase in blood cholesterol when the diet is copper deficient.
Dr Jack Saari of the Grand Forks Human Nutrition Research Center writes:
"Dietary copper deficiency causes a variety of cardiovascular deficits. Systemic effects include high blood pressure, enhancement of inflammation, anemia, reduced blood clotting, and possibly arteriosclerosis. Effects on specific organs or tissues include weakened structural integrity of the heart and blood vessels, impairment of energy use by the heart, reduced ability of the heart to contract, altered ability of blood vessels to control their diameter and grow, and altered structure and function of circulating blood cells."
After calcium, potassium is one of the most abundant minerals in your body. The balance between sodium and potassium is crucial and, unfortunately, the high sodium (salt) American diet can cause the potassium-sodium ratio to get seriously out of whack.
Potassium is essential for many functions in our bodies, particularly nerve activity and the healthy function of both voluntary and involuntary muscles. It regulates fluid balance, blood pressure, neuromuscular function, and protein and carbohydrate metabolism. Abnormalities in potassium levels in the body – both too much and not enough – can seriously affect cardiovascular function and can lead to cardiac arrest and death.
Research has shown that increased consumption of potassium helps to prevent high blood pressure. In 1991 in the Journal of Hypertension, Drs Cappuccio and MacGregor from the St. George's Hospital Medical School in London, recommended increasing dietary potassium as a non-drug way of controlling blood pressure. In a meta-analysis of 33 randomized trials of the effect of potassium on blood pressure, researchers from Johns Hopkins University School of Hygiene and Public Health found that potassium supplementation was associated with a significant reduction in both systolic and diastolic blood pressure. They also recommended an increased intake of potassium for the prevention and treatment of high blood pressure.
Chocolate is a good source of potassium and has very little sodium, thus maintaining the correct balance of these two minerals. In helping to restore the correct ratio between potassium and sodium, chocolate can once again help to keep your cardiovascular system healthy.
Saturated fat is often regarded as the big villain and it has received some very bad press over the last twenty years or so. Because the cocoa butter in chocolate contains some saturated fat it is generally seen as being bad for you and bad for your heart. This is because the consumption of saturated fat is believed to cause blood cholesterol levels to rise.
However, it is interesting to note that Dr Tom Sanders from King's College in London, pointed out in 2003 that the benefits of reducing the proportion of energy obtained from fat below 30% is not supported by experimental evidence. This was reiterated in 2004 by Dr Bruce German and Dr Cora Dillard, who wrote in the American Journal of Clinical Nutrition that "advice to decrease total fat intake has failed to have any effect on the prevalence of obesity, diabetes, and cardiovascular disease."
The scientific community looks set to argue about this issue for some time, so in the meantime let’s take a closer look at the fat in chocolate.
As long ago as the mid 1960s researchers knew that cocoa butter had a neutral effect on cholesterol; despite high levels of saturated fat, cocoa butter does not raise levels of bad cholesterol.
Cocoa butter is about one third oleic acid which is a monounsaturated vegetable oil the same as is found in olive oil. Oleic acid has been shown to have a slight cholesterol-lowering effect. Among a large body of research on this subject, there is a 1999 study by Dr Penny Kris-Etherton, and her colleagues from the Pennsylvania State University, which found that monounsaturated fatty acids, including oleic acid, lowered LDL cholesterol and triglycerides levels without lowering HDL cholesterol.
So we can push one third of the fat in chocolate aside knowing that not only is oleic acid not bad for us, but it is good for us.
Approximately another third of the fat in cocoa butter is stearic acid – a saturated vegetable oil. However, research has shown that despite being a saturated fat, stearic acid doesn’t raise the cholesterol levels in your blood and it is converted to monounsaturated oleic acid by a special enzyme in the liver. Again, researchers from the Pennsylvania State University found that stearic acid did not raise either the total cholesterol levels or levels of LDL and HDL cholesterol in the blood of either men or women. Earlier research by the same scientists found that stearic may have an independent cholesterol-lowering effect.
That is another third out of the way.
The last third of the fat in cocoa butter is the saturated fat palmitic acid. It does have a cholesterol raising effect, but the good news is that saturated fats do have an important role in our diet and health. For example, saturated fats help to protect us against skin cancer, whereas polyunsaturated fats don’t.
However, we need to look at the impact of the oleic, stearic and palmitic fats in combination as that is how they are found in cocoa butter.
In 1993 the results of study looking at the effects of cocoa butter, olive oil, soybean oil, dairy butter, and milk chocolate on blood lipids (fats) in young men was published in the journal Metabolism. In this randomized cross-over* clinical study healthy young men consumed four different experimental diets: 10 ounces of milk chocolate; a similar amount of cocoa butter on its own; cocoa butter and enough dairy butter to closely resemble the composition of milk chocolate; dairy butter alone. Each of the experimental diets contained the same amount of saturated fat. The study found that only the dairy butter diet significantly increased total and LDL cholesterol levels.
In a later study, published in the American Journal of Clinical Nutrition in 1994, in which the effects of a milk chocolate bar was compared with a high-carbohydrate snack in healthy young men, the milk chocolate was found to increase HDL cholesterol and lower blood triglycerides. The milk chocolate did not raise LDL cholesterol levels and this study showed that chocolate is better for your cholesterol profile than a high-carb snack. The researchers found that the high stearic acid content of milk chocolate was responsible for its lack of effect on LDL cholesterol.
Whichever view turns out to be correct – that a high fat diet contributes to heart disease, or that decreasing fat intake has not lowered the levels of cardiovascular disease in America or the rest of the developed world – we should keep in mind just how much fat chocolate contributes to our diets. In reality, chocolate is a relatively insignificant source of fat and generally contributes less than two percent of dietary fat, while meat, dairy products and grains are primary sources of fat, and ready-to-eat and "fast" foods are a significant source of fat.
* - The volunteers consumed each experimental diet for a period of time, then had a one month wash out period before “crossing-over” and consuming another experimental diet.
There isn’t any!
What more do we need to say. Good quality dark chocolate doesn’t contain cholesterol.
But, I guess, if we are going to be honest, not everyone is going to stick to eating good quality dark chocolate. Some of you with cravings for milk chocolate – and we know that there are a lot of you who prefer milk chocolate – are going to, even with the best of intentions, choose to eat milk chocolate.
So let’s have a look at the cholesterol issue.
First, as I said, dark chocolate does not contain cholesterol. Cholesterol is specifically an animal fat, so dark chocolate that is just cocoa butter and cocoa powder and sugar (with maybe a little lecithin), does not contain cholesterol. As soon as you add milk to it… well, here comes the cholesterol.
But there is a contradiction. In the research that we have just discussed – in which milk chocolate was pitted against a high-carb snack and the milk chocolate won – shows that the stearic acid content of milk-chocolate seems to cancel out any negative effect of the small amount of cholesterol from the milk.
Chocolate Antioxidants and Your Heart
The flavanol anti-oxidants in dark chocolate do all the things that we have just talked about. The action of these flavonols effectively work to stop heart disease before it starts, particularly when it comes to preventing or reducing the oxidation of LDL cholesterol.
We are going to have a closer look at the health of the lining of your arteries, clotting and high blood pressure a bit later, but first let’s look at the amazing research on cocoa, chocolate and cholesterol.
Some of the most recent research is potentially the most exciting for our hearts. Scientists from the Research Institute of Public Health, at the University of Kuopio in Finland published their findings in the journal Free Radical Biology and Medicine in November of 2004.
Dr Jaakko Mursu and his colleagues investigated the effects of long term consumption of chocolate containing differing levels of polyphenols on blood cholesterol levels and on the oxidation of the cholesterol. They under-took a three-week trial with 45 healthy, non-smoking volunteers. The participants ate 75 grams of either white chocolate, dark chocolate, or dark chocolate enriched with cocoa polyphenols each day. In both the dark chocolate and enriched dark chocolate groups there was an increase in the HDL levels (11.4% and 13.7%, respectively), whereas in the white chocolate group there was a small decrease (-2.9%). The concentration of LDL cholesterol decreased 11.9% in all three groups.
The researchers concluded that "cocoa polyphenols may increase the concentration of HDL cholesterol, whereas chocolate fatty acids may modify the fatty acid composition of LDL and make it more resistant to oxidative damage."
(Wow! You can actually increase the amount of good cholesterol by eating dark chocolate.)
Mursu’s work confirmed earlier studies published in 2001 by Dr Penny Kris-Etherton and her colleagues at Pennsylvania State University. They found that, in the 23 volunteers they studied, diets enriched with dark chocolate and cocoa powder raised HDL cholesterol. The researchers put the participants on an "average American diet" (AAD) or a diet that included 22 grams of cocoa powder and 16 grams of dark chocolate (CP-DC). Participants consumed each diet for four weeks followed by a brief break of two weeks before crossing over to the other diet. During the two week break between feeding periods, they continued with their usual, non-study, diet. The researchers wrote that "serum HDL cholesterol was significantly greater (by 4%) when subjects consumed the CP-DC diet compared with the AAD."<…>
As early as 1996 researchers were talking about the ability of chocolate and cocoa to limit or reduce the oxidation of LDL cholesterol. In many ways this should not have been a surprise to anyone. For decades the ability of chocolate to limit oxidation had been recognised even if its significance hadn’t been. After all, chocolate keeps for a very long time, and despite a high fat content doesn’t go rancid. This is why it was regarded as such an ideal food in war time and was included in army rations, even for soldiers on active duty.
Since the mid 1990s there has been quite a volume of research on the subject. While it would be a bit repetitive to go over the details of all the studies on LDL oxidation and chocolate – after all, how many times can you say how wonderful chocolate is – it is pertinent to have a brief look at some of the published research.
In 1999, Dr Joe Vinson and his team reported in the December issue of the Journal of Agricultural and Food Chemistry, that the flavonols in chocolate are more powerful than antioxidants such as vitamin C in limiting the oxidation of cholesterol circulating in low-density lipoproteins and very-low-density lipoproteins. About the same time Dr Cesar Fraga of the University of Buenos Aires demonstrated that the procyanidins in chocolate protected lipids (or fats) circulating in the blood from oxidation. He told an American Association for the Advancement of Science meeting in February 2000, that the more chocolate eaten, the better the protection. He believes that the procyanidins may function as a first line of defence against damaging oxidants – sparing vitamin C and other antioxidant vitamins that would otherwise be destroyed.
Half a world away Japanese scientists were studying the effect of cocoa powder on the oxidation of plasma components in the blood of rats. They found that the flavanol epicatchin was absorbed from the digestive tract of the rats and went on to enhance the anti-oxidant qualities of blood plasma, significantly reducing the oxidation of blood cholesterol.
In a large review of existing research Dr Penny Kris-Etherton, a distinguished professor of nutrition at Penn State University, and Dr Carl Keen, Head of the Department of Nutrition at University of California at Davis, looked at the results of 66 published studies on cocoa, chocolate and cardiovascular health. Their review was published in 2002 in Current Opinions in Lipidology. One of the most important protective mechanisms was found to be that flavonols in tea and chocolate helped to prevent oxidative damage to LDL cholesterol.
When discussing the research Dr Kris Etherton said: "No single food will confer immunity from illness. But both tea and chocolate, which are plant foods, can be components of a healthy diet if eaten in moderation along with other flavonoid-rich plant foods, such as fruits and vegetables. It's important to include a wide variety of plant foods in your diet every day."
I could go on for another few pages detailing the studies that have demonstrated the beneficial effect of chocolate and cocoa on cardiovascular health by preventing the oxidation of LDL cholesterol. Research on this incredibly exciting (and delicious) way of improving heart health is continuing and the news is likely to only get better for chocolate lovers. However, if you feel the need for more convincing of the cardiovascular benefits of chocolate, I invite you to peruse the medical literature and check out the dozens of papers on this for yourself.
I think the words of a number of researchers from the Departments of Nutrition and Internal Medicine at the University of California at Davis, published in the Journal of Nutrition in 2000, summarise well the findings of a considerable volume of research over the last five to ten years:
"Given the results of the current study, as well as the findings of others, we suggest that the daily consumption of procyanidin-rich foods, such as chocolate, can result in improvements in the antioxidant potential of plasma."
OTHER CHOCOLATEY EFFECTS ON YOUR HEART
Hardening of the Arteries and Endothelial Function
Wow, that’s a mouthful. And a mouthful of dark chocolate will help.
Hardening of the arteries? Well, that’s the atherosclerosis that we talked about at the beginning of this chapter when we had a look at the components of heart disease. The endothelium is the name for the cells that line the cavities of the heart and the blood vessels. The endothelium is involved with constriction and dilation of the blood vessels and hence the control of blood pressure. It is also involved with blood clotting, atherosclerosis, inflammation and swelling. Atherosclerosis involves chronic injury to the endothelium. If the endothelium isn’t functioning as it should – either because it stiffens and contracts or because it is clogged up with plaque – the blood vessels may be constricted and narrow, reducing blood flow.
Dr Mary Engler and her colleagues reported in 2004 that small daily doses of flavonoid-rich dark chocolate, consumed over a two-week period, improved endothelial function, thus improving the ability of the blood vessels to expand or dilate. They also found that concentrations of epicatechin, the flavonoid believed to be particularly beneficial for endothelial function, were markedly increased after two weeks in the group of volunteers eating the flavonoid-rich chocolate. <…>
The clotting of blood in the arteries is a significant factor in cardiovascular disease. As we discussed earlier in this Chapter, a clot that occurs inside the artery is called a thrombus and when it’s on the move it is called an embolus. Emboli move around in our bloodstream until they lodge in a narrowed artery and block circulation. The formation of a thrombus is one of the main problems in ischaemic heart disease and they are the cause of most cases of sudden deterioration in angina and most heart attacks.
This clotting of blood, or platelet aggregation, is such a problem for some people that they take blood thinning drugs, such as aspirin, every day to reduce the risk of blood.
Blood thinning drugs or…
Yes, try chocolate for thinning the blood.
That’s right, another amazing effect of the antioxidants in chocolate is that they reduce the level of platelet activity and adhesion, keeping blood platelets from making the blood too thick and sticky, thereby reducing the occurrence of clots.
Scientists had speculated for some time that dietary polyphenols could protect the heart and improve cardiovascular health owing to direct anti-thrombotic or anti-clotting mechanisms. In 2000 scientists from the University of California found that when purified cocoa procyanidins were incubated with human blood in the laboratory, the procyanidins inhibited platelet activation and aggregation. In the same study 40 healthy men and women consumed either a cocoa drink, de-alcoholized red wine, a caffeine-containing drink or water. Their blood was tested two hours and six hours after the drinks and platelet activation was measured in the blood. Only the blood of the volunteers that had consumed the cocoa drink showed significant platelet inhibition. <…>
High Blood Pressure
We all probably know what it is like, know how it feels as the blood pressure rises. There are numerous triggers, but emotional ones are possibly the ones most familiar to us – stress, anxiety, anger, fear.
For those of us who are "chocoholics" the sweet sensual pleasure of chocolate may soothe a furrowed brow and calm a turbulent mind. The sheer pleasure of chocolate is enough to erase the stresses of the day for some.
But what if there were compounds in chocolate that could actually, physically lower blood pressure? And, after all you have learnt about chocolate, would you really be surprised?
Not only does chocolate make you feel good but it can help to lower your blood pressure and in doing so protect your arteries from damage that can lead to heart disease.
In one study, researchers from the University of Cologne in Germany investigated the effect of dark chocolate containing 500mg of polyphenols on the blood pressure of 13 volunteers aged between 55 and 64 years of age. Each of the six men and seven women had been recently diagnosed with untreated stage 1 mild systolic hypertension. On average their blood pressure before the study commenced was 153 over 84 (normal blood pressure is 120 over 80). They were randomly assigned to one of two groups – one group was given daily doses of the polyphenol rich dark chocolate and the other group daily doses of white chocolate with only 90 mg of polyphenols. The chocolate consumption continued for 14 days, then both groups abstained from chocolate for seven days (that must have been an effort!) then switched to the other chocolate. To ensure that they weren’t increasing their calorie intake they were asked to balance their energy intake by not eating other foods similar in nutrients and calories.
Within ten days of the start of the study, those eating the dark chocolate had shown significant reductions in both systolic and diastolic blood pressure. After 14 days on the dark chocolate the blood pressure of the volunteers had dropped an average of five points on their systolic reading and 1.8 points on their diastolic reading!
But, wait! The good news is that you have to keep on eating the dark chocolate. What a hardship!
When the study volunteers stopped eating the dark chocolate their blood pressure returned to their previous levels within two days. Interestingly the chocolate had no effect on heart rate and there was no difference between the men and women. Dr Dirk Taubert and his study colleagues believe that the polyphenols in the dark chocolate may have "significant bioavailability". This may mean that it is easier for the body to absorb them and use them in beneficial ways.
This is supported by research carried out by Italian scientists. Mauro Serafini, and his colleagues from the Antioxidant Research Laboratory at the National Institute for Food and Nutrition Research in Rome. They found that eating dark chocolate results in an increase in both the total antioxidant capacity and the epicatechin content of blood plasma. Unfortunately for milk chocolate lovers the same study found that the "effects are markedly reduced when the chocolate is consumed with milk or if milk is incorporated as milk chocolate." Dr Serafini concludes that "milk may interfere with the absorption of antioxidants from chocolate… and may therefore negate the potential health benefits that can be derived from eating moderate amounts of dark chocolate."
Atherosclerosis, the main player in cardiovascular disease, is an inflammatory disease process, in which the lining of the blood vessels are damaged, followed by a succession of inflammatory responses to that damage. We’ve seen that oxygen free radicals or oxidised LDL can injure the lining of the blood vessels, as can untreated high blood pressure and exposure to tobacco smoke. Drs Hannum, Schmidt and Keen describe the process that follows injury:
"As a result of the injury, the endothelium becomes more permeable, attracts monocytes and other inflammatory and immune cells, and becomes more adhesive for platelets and leukocytes."
All this means that there is a build up of material – plaque – on the inside of the artery, all because of the damage done to the cells lining the blood vessel.
Several studies published in the last five years have demonstrated that cocoa flavonols can reduce the production of inflammatory cytokines – proteins that are secreted by inflammatory white blood cells – while increasing the production of anti-inflammatory cytokines, as well as decreasing the level of leukotrienes – a hormone like compound which sustains inflammatory reactions and is involved in constricting blood vessels.
By reducing the inflammatory response, it seems that cocoa flavonols contribute to cardiovascular health in yet another way.
This is the bit that I like the best. This is where I get to tie up all the loose ends and can tell you that overall, and in moderation (like all good things), chocolate is good for your heart.
We’ve come full circle… At the beginning of the twenty-first century we are finally realising the benefits of dark chocolate; five hundred years after Hernén Cortéz and his followers discovered the Aztecs drinking it for strength, energy and health, four hundred and fifty years after the monks and nuns of Europe were using it as a medicine and two hundred years after Antonio Lavedan wrote that chocolate "vivifies the substance of the heart".
This is no longer about some faded texts from the history books. This is real science telling us what deep in our hearts some of us have known for centuries. One of the important points to remember is that many of the studies we have looked at have actually measured the levels of antioxidant epicatechin, catechin and procyanidin in the blood and the urine of human participants. While making such amazing discoveries about chocolate in the test-tube is the first step, it is important to ensure the bio-availablity of the antioxidants from chocolate in real people. Such human studies have confirmed what all chocolate lovers must have hoped for – chocolate really does have these effects and benefits when we eat it. Interestingly, some of these studies have used commercial chocolate products, such as M&M'S® Brand Semi- Sweet Chocolate Mini Baking Bits and DOVE® Dark Chocolate Bar, rather than any specially concocted chocolates.
Dose is also important, and I know you will all want to know how much you can or should eat. Drs Penny Kris-Etherton and Carl Keen said that the results of their work indicated that 38 grams, or about one and a third ounces, of flavonoid-rich dark chocolate produces an immediate (acute) effect and 125 grams, or about four and a half ounces, produces a continuing (chronic) effect.
Dr Norman Hollenberg of Harvard Medical School in Boston, says "the issue isn't should we or should we not be recommending chocolate. The fact is, we are eating chocolate… The new data suggest that, unless [they] overindulge, people should not feel guilty about eating it."
"We can drop our twinges of guilt as we enjoy cocoa and chocolate foods, as long as they are in moderation and part of a healthful balanced diet."
Drs Hannum., Schmitz and Keen in Chocolate: a Heart Healthy Food?
"I have this theory that chocolate slows down the aging process... It may not be true, but do I dare take the chance?"
The DASH study also suggested that high blood pressure could be significantly lowered by a diet high in magnesium. This is supported by several other studies, including a study by the Harvard School of Public Health of more than 30 000 men, published in Circulation in 1992, which found that a greater magnesium intake was significantly associated with a lower risk of high blood pressure. In fact the evidence for magnesium’s role in reducing blood pressure is so strong that in 1997 the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure recommended that an adequate magnesium intake was a positive way of both preventing and managing high blood pressure.
"Many people don't realize that chocolate is plant-derived, as are the fruits and vegetables recommended for a healthy heart."
Dr Mary Engler, University of California, San Francisco