Originally published September 24 2008
Why Chocolate Is Good for Your Heart
by Helmut Beierbeck
(NaturalNews) Can't live without dessert? Forget about ice cream and cakes, and go for dark chocolate! It′s actually good for you -- in moderation of course. Chocolate and cocoa are made from the cacao bean, one of the richest sources of flavanols, a group of polyphenolic antioxidants. The major flavanols in chocolate, catechin and epicatechin, are structurally similar to the antioxidants found in red wine and grapes, and in tea. Chocolate is actually the third-leading source of antioxidants in the U.S. diet, after coffee and tea (1).
Flavanols -- and therefore chocolate and cocoa -- promote cardiovascular health in a number of ways.
Cocoa flavanols help prevent lipid oxidation
To confirm the antioxidant properties of chocolate flavanols, investigators studied the effect of chocolate on the rate of lipid oxidation and on the extent of atherosclerosis -- plaque containing oxidized low-density lipoproteins (2).
In the first experiment human plasma was incubated with either a water/methanol mixture (control) or a water/methanol chocolate extract, to bind any flavanols to the lipoproteins. The low-density lipoproteins (LDL and VLDL) were then isolated from the treated plasma solutions. A divalent copper oxidant was added to each of the two solutions, and the rate of appearance of oxidized fatty acids was measured. The lipoproteins from the chocolate-treated plasma remained unoxidized significantly longer than the control, i.e. the lipid-bound flavanols helped protect the lipoproteins against oxidation.
In a second experiment, subjects were given muffins with or without (control) chocolate for breakfast, followed by a normal lunch and dinner. At regular intervals blood samples were taken, the lipoproteins were isolated and treated with divalent copper ions. Again, the lipoproteins from the plasma of the participants eating the chocolate-containing muffins resisted oxidation by the copper ions significantly longer than the lipoproteins from controls.
In a third experiment, this time on animals, the extent of atherosclerosis as function of chocolate intake was measured directly. Hamsters were fed a diet high in saturated fat and cholesterol that also contained high or low amounts of chocolate, or none at all (controls). After ten weeks the animals were sacrificed, their aortas removed and examined for atherosclerotic lesions -- the fatty streaks containing oxidized lipoproteins. The hamsters on the low and high chocolate diets had about 40% fewer lesions than the controls. The lesions were somewhat smaller in the low-chocolate group, presumably because the high-chocolate diet contributed more unsaturated fatty acids which are also prone to oxidation.
As these results show, the flavanols in chocolate indeed help prevent oxidative damage and protect against atherosclerotic plaque formation.
Cocoa flavanols improve blood flow
To investigate the effect of cocoa flavanols on blood vessel dilation and blood flow, sixteen healthy young men were recruited for a randomized, double-blind cross-over study (3). The participants were randomly assigned to drink cocoa that was either high or low in flavanols. At the midpoint of the study the drink assignments were reversed, i.e. every subject′s low-flavanol results served as control. The investigators measured blood flavanol levels, flow-mediated dilation of blood vessels (FMD -- a surrogate marker of cardiovascular events), and nitric oxide (NO) production (necessary for blood vessel dilation).
To confirm flavanol absorption, the subjects were given either low- or high-flavanol cocoa to drink. Blood samples were taken before drinking the cocoa and after 1, 2, 3, 4, and 6 hours. After the high-flavanol cocoa the blood levels of the various flavanols were significantly higher than in the low-flavanol phase, demonstrating that the cocoa flavanols were indeed absorbed. Epicatechin derivatives showed the greatest increase.
To assess the effect of flavanols on blood vessel function and blood flow, flow-mediated dilation (FMD), a non-invasive measurement of endothelial function, was followed as function of time and type of cocoa. The investigators found that blood vessel dilation (increase in diameter) varied with the rise and fall of blood levels of epicatechin and its derivatives.
Blood vessel dilation requires nitric oxide (NO) production. Indeed, measurement of nitric oxide and its metabolites in blood and urine were found to closely match variations in flavanol levels and blood level dilation. When nitric oxide synthesis was prevented by injecting an enzyme inhibitor, blood vessel dilation was abolished, confirming the role of NO.
Finally, when the subjects drank water containing pure epicatechin instead of cocoa, the same increase in nitric oxide production was observed, i.e. it was indeed the epicatechins in cocoa that were responsible for the increase in NO levels, which in turn increased blood vessel diameters.
In summary, cocoa improves blood flow, and epicatechin and its derivatives are responsible for that effect.
Cocoa flavanols reduce the risk of blood clotting
Ruptured atherosclerotic plaque is a potent platelet activator. Increased platelet reactivity and spontaneous aggregation are associated with a higher risk of coronary artery disease. Aspirin is the drug of choice to reduce the risk of blood clot formation. Would chocolate flavanols do the same thing?.
Thirty healthy men and women were recruited to study the effect of flavanol-rich cocoa on platelet activation and on the rate of hemostasis (prevention of blood loss through damaged blood vessels) (4). The subjects were given one of three drinks, either a flavanol-rich cocoa drink made with water, caffeine in water (to assess the effect of the caffeine in cocoa), or pure water. Blood samples were drawn 2 and 6 hours later and the blood was subjected to three different tests.
The first test measured the comparative extent of platelet activation after cocoa consumption. This was done by treating each solution with fluorescent-labelled antibodies that only bound to surface proteins on activated platelets. The amount of fluorescence in the platelet fractions therefore indicated the degree of platelet activation. The percentage of activated platelets was found to be lower after cocoa consumption than after drinking water/caffeine or pure water.
The second test measured the number of platelet microparticles -- hemostatically active microvesicles. The exact function of these microparticles is unclear, but their levels are a reflection of platelet aggregation. The number of microparticles detected after cocoa consumption decreased, whereas it increased after water/caffeine or water.
The third test looked at the time it took for hemostasis to occur after consumption of cocoa, water/caffeine or water. This was done by measuring the time it took platelets to close a small aperture in a test cartridge in the presence of collagen and either epinephrine or ADT (needed to turn a soft platelet aggregate into a firm clot). Six hours after cocoa consumption epinephrine-induced closure was slowed; ADT had no such effect.
These results show that cocoa, like aspirin, affects platelet clumping. This means that the effects of aspirin and chocolate on platelets are additive!
What kind of chocolate and how much should one eat for optimum health benefits?
The higher the cocoa percentage, the greater the flavanol content and the health benefits of the chocolate or cocoa. Therefore, dark chocolate is best; milk chocolate is a watered-down, much less effective product. Go for chocolate with 70% or more cocoa butter. It′s the best-tasting chocolate anyway, at least in this chocoholic′s opinion.
How much is healthiest? Nobody really knows. On one hand, the more chocolate one eats, the more flavanols one gets. On the other hand, chocolate and cocoa aren′t exactly calorie-free. Cocoa contains fat (cocoa butter), primarily oleic, palmitic and stearic acids. The monounsaturated oleic acid is heart-healthy, but it is also prone to oxidation. Triglycerides containing stearic acid actually raise HDL ("good cholesterol") levels. Still, they obviously add to the total calories. In addition, chocolate also contains sugar.
Remember too that chocolate adds to the anti-clotting effect of aspirin. So if you take aspirin and "self-medicate" with chocolate, your doctor should know about it.
Dark chocolate -- an indulgence that is actually good for you!
Sources:
1. Alspach G. Chocolate does a heart good. Critical Care Nurse 2007;27:11-15.
(http://ccn.aacnjournals.org/cgi/reprint/27/1...)
2. Vinson JA et al. Chocolate is a powerful ex vivo and in vivo antioxidant, an antiatherosclerotic agent in an animal model, and a significant contributor to antioxidants in the European and American diets. J Agric Food Chem 2006;54(21):8071-8076.
(http://pubs.acs.org/cgi-bin/sample.cgi/jafca...)
3. Schroeter H et al. (-)-Epicatechin mediates beneficial effects of flavanol-rich cocoa on vascular function in humans. Proc Nat Acad Sci 2006;103(4);1024-1029.
(http://www.pnas.org/content/103/4/1024.full....)
4. Rein D et al. Cocoa inhibits platelet activation and function. Am J Clin Nutr 2000;72:30-35.
(http://www.ajcn.org/cgi/reprint/72/1/30)
About the author
Helmut Beierbeck has a science background and a strong interest in all scientific aspects of health, nutrition, medicine, weight loss, or any other topic related to wellness. You can follow his ruminations on his blog http://healthcomments.info and leave comments on this or any other health-related topic.
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