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Dark Chocolate Controversy

July 22, 2009 Written by JP    [Font too small?]

While conducting some research this morning, I made an unexpected connection between meditation and politics. When meditating we are often instructed to gently observe our thoughts, no matter where they lead. They’re simply benign messengers of the subconscious mind. In politics, ideally we strive to observe current events, then dispassionately incorporate that information into our political views. I think the application of scientific research should be approached in a similar manner. In a nutshell, I believe we need to be aware and open to new research that both supports and, occasionally, contradicts our points of view. I discovered an example of this while reviewing the most recent data on the effects of dark chocolate on hypertension.

In recent years, many studies have suggested a positive association between dark chocolate consumption and cardiovascular health. This connection appears to be due to cocoa’s beneficial impact on blood pressure, circulation, inflammation and lipid levels (cholesterol and triglycerides). (1) But several new trials point to some degree of controversy as to whether or not dark chocolate is actually effective in lowering blood pressure in a real world setting.

On July 22nd a promising experiment was made public in the Journal of Agricultural Food Chemistry. The results demonstrated that a flavonoid-rich cocoa powder produced anti-hypertensive effects that were comparable to a commonly used blood pressure medication (Captopril). The fact that the blood pressure lowering activity was only observed in test animals that had high blood pressure, but not those with normal levels, was also encouraging. (2)

Just two weeks prior, another trial was presented in a different medical journal devoted to the study of alternative and complementary medicine. That experiment was conducted in a group of 36 adults with “prehypertension”. During the active stage of the study, they all consumed a 50 gram serving of a dark chocolate bar containing 70% cocoa and standardized for 750 mg of polyphenols (a class of antioxidants). To the researchers’ surprise, no significant impact on blood pressure was noted in this experiment. (3)

This is where the controversy begins. One study says that dark chocolate can improve blood pressure and another disputes that contention. There are a number of factors that need to be considered when trying to make sense of this discrepancy. First, it’s important to remember that the negative study was conducted with human subjects. This lends more credibility to that research than to the first trial that used test animals (rats). Secondly, the form of cocoa used in each experiment may also be a factor. The rat study used an unsweetened cocoa powder, while the human study involved a dark chocolate bar that contained added ingredients, including sugar.

There is a growing body of research that draws an association between carbohydrate and sugar intake and elevated blood pressure. (4,5,6) It could be that the added sugar in the candy bar used in the human trial negated the anti-hypertensive effects that were experienced in the rat study. Another possibility is that other additives in the chocolate bar may have impeded the absorption of the health promoting components of pure cocoa. Or, perhaps the discrepancy can be explained by how humans and rats metabolize the active ingredients found in cacao extracts differently. (7,8)

There are certainly more questions than answers that arise with these new findings. But there are a few heart pleasing actions of cocoa consumption that are not in question. The first thing we know is that pure cocoa powders consistently improve circulation, even in instances where blood pressure remains unaffected. This is certainly a positive consequence for most people who are interested in promoting overall cardiovascular health. (9,10)

Source: BMC Complement. Altern. Med. Published online July 8, 2009 (link)

It’s also important to note that a human study published in the Journal of Nutrition in 2008 did detect a significant blood pressure lowering effect in those using a “flavanol-rich dark chocolate” extract. (11) That trial was conducted on a group 19 hypertensive men and women with impaired glucose tolerance (IGT) and employed a 100 gram daily serving of dark chocolate (double the amount used in the most recent study). Another difference is that it lasted only 15 days. Within that shorter time period, the following findings were reported:

  • The cocoa extract induced improvements in insulin sensitivity and decreased insulin resistance.
  • Those consuming the dark chocolate also exhibited drops in diastolic and systolic blood pressure.
  • Improvements were also found in circulatory markers and reductions in LDL “bad” and total cholesterol were observed.

The experimental chocolate used in the 2008 trial was defined as being “low-energy cocoa”. This refers to the amount of calories present, which would normally come primarily from fat and sugar. Again, this points to the possibility that sugar and/or a higher dosage of cocoa may be more effective than what was used in the most recent, unsuccessful human trial.

Even if it turns out that high quality cocoa doesn’t lower blood pressure, it won’t discourage me from including it in my daily routine. The amount of evidence pointing to the health promoting properties of cocoa is simply overwhelming and unlikely to change in the coming years. What needs to be determined is how to best utilize this superfood. How much should be eaten? What form of cocoa will yield the greatest benefit? Are there competing nutritional factors, such as sugar, that may negate cocoa’s cardiovascular benefits? Only science can help identify the answers to these and other related questions. I’ll be on the lookout for the answers to those questions and will certainly make sure to report my findings here.

Note: Please check out the “Comments & Updates” section of this blog – at the bottom of the page. You can find the latest research about this topic there!

Be well!


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Posted in Food and Drink, Heart Health, Nutrition

15 Comments & Updates to “Dark Chocolate Controversy”

  1. Kyle Says:


    All this begs the question: Is it not better to use simple Cocoa powder in skim milk rather than dark chocolate to bring down LDL levels?


  2. JP Says:


    I’m not certain that the skim milk is necessary. High-flavanol cocoa (without any dairy) has been shown to modestly lower LDL in some studies. But more importantly (in my opinion), it has frequently been shown to lower systemic inflammation, the oxidation of LDL cholesterol and to improve circulation.

    I usually mix a pure, organic cocoa powder (2-3 tablespoons) with some hot coffee and a stevia/inulin based sweetener. On occasion I add protein powder and/or organic coconut milk to the mix.

    PS – Pure cocoa is actually quite rich in fiber. That alone may help to slightly lower LDL cholesterol levels.

    Be well!


  3. Kyle Says:

    Thank you, JP. Two final queries.

    1. When you say coffee, do you mean black (the usual water-based) coffee with no cream or dairy products added?

    2. How about cocoa in just hot water with a teaspoon of sugar to get rid of the bitter taste?

    In other words, am I to understand that I avoid mixing cocoa with any dairy products?


  4. JP Says:


    I use black coffee (usually organic, instant coffee).

    Cocoa in hot water would be just fine, in my opinion. My personal preference is to avoid added sugar altogether. That’s why I use and recommend using stevia instead.

    I rarely add milk or cream to my hot cocoa or “ChocoCoffee”. I do however add (natural vanilla) egg or whey protein on occasion. When I want a creamier or milder taste … I generally add a few ounces of organic coconut milk. I specifically use coconut milk because of the health benefits associated with unrefined coconut oil.




    Be well!


  5. Stu Says:


    I encourage my Mom to eat dark chocolate for its potential health benefits (she doesn’t need much encouragement). I am a little confused by some of the studies that seem to indicate that milk negates the benefits of dark chocolate. I try to advise her to separate the consumption of the chocolate from dairy products period. Am I going too far? Is it milk itself that negates the positive effects or something common to all dairy products e.g. calcium. And if so, how much a separation time-wise should be made.

    Thanks in advance.


  6. JP Says:


    I encourage my parents to do the same. 🙂

    Most of the current studies conclude that mixing cocoa with milk isn’t a big deal. The benefits of cocoa appear to remain even in the presence of dairy ingredients. Having said that, the overall data-picture on the whole cocoa/milk issue is mixed:

    “Chocolate Milk” lowers inflammation – http://www.ajcn.org/cgi/content/abstract/90/5/1144

    No Significant Difference in Bioavailability – http://pubs.acs.org/doi/abs/10.1021/pr900470a



    Mixed Results – http://www.ajcn.org/cgi/content/abstract/89/6/1784


    Negative Results – http://content.karger.com/produktedb/produkte.asp?typ=fulltext&file=000111473

    Here’s my take on the issue: If your mom absolutely loves having her dark chocolate with a glass of milk … I wouldn’t be too concerned about it.

    Ideally, I think it would be best to eat or drink the dark chocolate apart from dairy. By that, I mean not at the same meal. In all likelihood, any change in absorption is probably due to a direct interaction between components of cocoa and milk fat and/or milk protein (casein) <--- the chief suspect. I hope this helps! Be well! JP

  7. Stu Says:

    Thanks JP:

    She actually doesn’t drink milk at all. It is more of an issue with something like yogurt. She’ll eat yogurt for lunch and then go for the dark chocolate a few minutes later. We actually got into a pitched battle yesterday. I was trying to persuade her to wait at least an hour or so before consuming the chocolate. My reasoning is that if you can get health benefits from something that enjoyable don’t risk negating them. But as I said before I am not entirely clear on what causes the negation. I had always thought that it took the body a very long time to digest dairy. So I was never really sure that an hour would even make a difference anyway unless as you say it is direct interaction.


  8. JP Says:


    I can understand your point of view. This is why I generally have my cocoa in the form of a pure dark chocolate or hot cocoa made with organic cocoa powder, stevia and organic coconut milk. I find it to be perfectly enjoyable that way.

    My hunch is that your mom will still find some/many benefits eating dark chocolate in the way she does.

    Be well!


  9. Stu Says:

    Thanks again JP:

    I buy large bars of the 72% strain of dark chocolate for her (other than a little sugar and soy lecithin it seems to be pure to me). Hopefully it will provide health benefits. Even if it doesn’t it still tastes darn good.


  10. Baine Says:

    Hey JP…

    I wanted to give the refrence of this article of yours.. can you tell me the APA citation of your article? please and thank you.

  11. JP Says:

    Dark Chocolate Update:


    Thromb Haemost. 2014 Sep 11;112(6).

    Effects of dark chocolate consumption on the prothrombotic response to acute psychosocial stress in healthy men.

    Flavanoid-rich dark chocolate consumption benefits cardiovascular health, but underlying mechanisms are elusive. We investigated the acute effect of dark chocolate on the reactivity of prothrombotic measures to psychosocial stress. Healthy men aged 20-50 years (mean ± SD: 35.7 ± 8.8) were assigned to a single serving of either 50 g of flavonoid-rich dark chocolate (n=31) or 50 g of optically identical flavonoid-free placebo chocolate (n=34). Two hours after chocolate consumption, both groups underwent an acute standardised psychosocial stress task combining public speaking and mental arithmetic. We determined plasma levels of four stress-responsive prothrombotic measures (i. e., fibrinogen, clotting factor VIII activity, von Willebrand Factor antigen, fibrin D-dimer) prior to chocolate consumption, immediately before and after stress, and at 10 minutes and 20 minutes after stress cessation. We also measured the flavonoid epicatechin, and the catecholamines epinephrine and norepinephrine in plasma. The dark chocolate group showed a significantly attenuated stress reactivity of the hypercoagulability marker D-dimer (F=3.87, p=.017) relative to the placebo chocolate group. Moreover, the blunted D-dimer stress reactivity related to higher plasma levels of the flavonoid epicatechin assessed before stress (F=3.32, p = .031) but not to stress-induced changes in catecholamines (p’s=.35). There were no significant group differences in the other coagulation measures (p’s≥.87). Adjustments for covariates did not alter these findings. In conclusion, our findings indicate that a single consumption of flavonoid-rich dark chocolate blunted the acute prothrombotic response to psychosocial stress, thereby perhaps mitigating the risk of acute coronary syndromes triggered by emotional stress.

    Be well!


  12. JP Says:

    Update: Enjoying dark chocolate judiciously can improve the health of overweight individuals …


    Journal of Nutritional Biochemistry – February 25, 2015

    Natural cocoa consumption: Potential to reduce atherogenic factors?

    Short-term consumption of flavanol-rich cocoa has been demonstrated to improve various facets of vascular health. The purpose of the present study was to determine the effect of 4 weeks of natural cocoa consumption on selected cardiovascular disease (CVD) biomarkers in young (19–35 years) women of differing body mass indices (BMI; normal, overweight or obese). Subjects (n=24) consumed a natural cocoa-containing product (12.7 g natural cocoa, 148 kcal/serving) or an isocaloric cocoa-free placebo daily for 4 weeks in a random, double-blind manner with a 2-week washout period between treatment arms. Fasted (>8-h) blood samples were collected before and after each 4-week period. Serum was analyzed to determine lipid profile (chemistry analyzer) and CVD biomarkers (26 biomarkers). EDTA-treated blood was used to assess monocytes (CD14, CD16, v11b and CD62L), while citrate-treated blood was used to measure changes in endothelial microparticles (EMPs; CD42a−/45−/144+) by flow cytometry. Natural cocoa consumption resulted in a significant decrease in haptoglobin (P=.034), EMP concentration (P=.017) and monocyte CD62L (P=.047) in obese compared to overweight and normal-weight subjects. Natural cocoa consumption regardless of BMI group was associated with an 18% increase in high-density lipoprotein (P=.020) and a 60% decrease in EMPs (P=.047). Also, obese subjects experienced a 21% decrease in haptoglobin (P=.034) and a 24% decrease in monocyte CD62L expression in (P=.047) following 4 weeks of natural cocoa consumption. Collectively, these findings indicate that acute natural cocoa consumption was associated with decreased obesity-related disease risk. More research is needed to assess the stability of the observed short-term changes.

    Be well!


  13. JP Says:

    Updated 1/26/16:


    Environ Monit Assess. 2016 Feb;188(2):86.

    Heavy metal content in various types of candies and their daily dietary intake by children.

    Children are vulnerable to heavy metal contamination through consumption of candies and chocolates. Considering this representative samples (69) of candies and chocolates based on cocoa, milk and sugar were analyzed for selected heavy metals by means of flame atomic absorption spectrometry. The average concentration of Zn, Pb, Ni, and Cd was found to be 2.52 ± 2.49, 2.0 ± 1.20, 0.84 ± 1.35, and 0.17 ± 0.22 μg/g respectively. Results indicate that cocoa-based candies have higher metal content than milk- or sugar-based candies. The daily dietary intake of metals for children eating candies and chocolates was also calculated, and results indicated highest intake of Pb and Zn followed by Ni, Cd, and Cu. Comparison of the current study results with other studies around the globe shows that the heavy metal content in candies and chocolates is lower in India than reported elsewhere. However, to reduce the further dietary exposure of heavy metals through candies and chocolates, their content should be monitored regularly and particularly for Pb as children are highly susceptible to its toxicity.

    Be well!


  14. JP Says:

    Updated 11/29/16:


    Clin Interv Aging. 2016 Nov 14;11:1645-1652.

    Habitual cocoa intake reduces arterial stiffness in postmenopausal women regardless of intake frequency: a randomized parallel-group study.

    Arterial stiffness is substantially higher in postmenopausal than in premenopausal women. Daily cocoa intake has been shown to reduce central arterial stiffness in health adults, regardless of age; however, the effect of cocoa-intake frequency on arterial stiffness in postmenopausal women remains unclear. Therefore, the purpose of this study was to investigate the effects of cocoa-intake frequency on arterial stiffness in postmenopausal women. A total of 26 postmenopausal women (mean age ± standard deviation 64±12 years) were randomly assigned to two groups with different cocoa-intake frequencies: one group ingested 17 g of cocoa once daily except on Sundays (every-day group, n=13), and the other ingested 17 g of cocoa twice daily every other day (every-other-day group, n=13). These intake regimens were maintained in both groups for 12 weeks. Carotid-femoral pulse-wave velocity and femoral-ankle pulse-wave velocity were measured in both groups at baseline and again at the end of the 12-week study period. Compared to baseline, both pulse-wave velocities had significantly decreased after the 12-week study period in both groups (P<0.05). However, no significant difference in degree of change was observed between the two groups. Although this study did not include a sedentary control group, these results suggest that regardless of frequency, habitual cocoa intake reduces central and peripheral arterial stiffness in postmenopausal women.

    Be well!


  15. JP Says:

    Updated 03/19/17:


    J Food Prot. 2017 Mar 17:692-702.

    A Limited Survey of Dark Chocolate Bars Obtained in the United States for Undeclared Milk and Peanut Allergens.

    Undeclared allergens in chocolate products have been responsible for numerous allergen-related recalls in the United States. A survey was conducted to determine the prevalence of undeclared milk and peanut in 88 and 78 dark chocolate bars, respectively. Concentrations of milk (as nonfat dry milk) or peanut in three samples of each chocolate product were determined with two milk- or peanut-specific enzyme-linked immunosorbent assay kits. In 75% of the chocolate bar products with a milk advisory statement, milk concentrations were above the limit of quantitation (2.5 μg/g [ppm]), with the majority having concentrations >1,000 ppm. An additional 67% of chocolate bars with a “traces of milk” statement contained 3 to 6,700 ppm of milk. Fifteen percent of chocolates labeled dairy free or lactose free and 25% labeled vegan were positive for milk, all with concentrations >1,000 ppm. Even for chocolates with no reference to milk on the label, 33% of these products contained 60 to 3,400 ppm of milk. The survey of chocolate products for peanuts revealed that 8% of products with an advisory statement contained peanut, with the highest concentration of 550 ppm. All nine chocolates bearing the peanut-free or allergen-free statement were negative for peanut, but 17% of chocolates with no label statement for peanut were positive for peanut at concentrations of 9 to 170 ppm. Evaluation of multiple lots of four chocolate products revealed that milk was consistently present or absent for the products investigated, but mixed results were obtained when multiple lots were tested for peanut. This study indicates that a large proportion of dark chocolate bars contain undeclared milk. The type of advisory statement or the absence of a milk advisory statement on products did not predict the amount or absence of milk protein. In contrast, a lower proportion of chocolates containing undeclared peanut was found. Consumers with food allergies should be cautious when purchasing dark chocolate products, particularly those that have an advisory label statement.

    Be well!


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