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Dark Chocolate Put to the Test for Peripheral Artery Disease

One of the problems with publishing research on chocolate is that the press jumps on it, oversimplifying and sensationalizing the message, and then the money starts rolling in from candy companies and the message is muddied even more. As a result, an important idea is lost in all the frenzy: The flavanol phytonutrients in cocoa appear to be beneficial, as I discuss in my video Chocolate and Stroke Risk. Though the sugar, fat, and excess calories in chocolate aren’t good for us, “natural cocoa powder can be a health food.” So, adding cocoa to a smoothie or oatmeal, for example, would be health-promoting. Try to use unprocessed, undutched cocoa, though. The beneficial flavanols are what give cocoa its bitterness, so manufacturers try to process cocoa with alkali to destroy them on purpose. Thus, when it comes to cocoa, bitter appears to be better.

In my previous video Dark Chocolate and Artery Function, you can see how high-tech angiography showed that dark chocolate could improve the function of coronary arteries in the heart within two hours of consumption, but there are some blood vessels you can visualize with your own eyes: the blood vessels in your eyes. Two hours after eating dark chocolate, as I show at 1:18 in my Chocolate and Stroke Risk video, you can observe a significant improvement in the ability of the little veins in your eyes to dilate.

What about the blood vessels in our legs? Peripheral artery disease (PAD) is atherosclerosis in the arteries feeding our limbs, which leads to claudication, a crampy pain in our calf muscles when we try to exercise, due to impaired blood flow. So, maximal walking distance and time were studied in 20 PAD patients two hours after subjects ate either dark chocolate with at least 85 percent cocoa or milk chocolate with no more than 35 percent cocoa. After eating the dark chocolate, the subjects could walk about a dozen more yards and about 17 seconds longer than before they had the dark chocolate. In comparison, after the milk chocolate, they weren’t even able to walk as far as baseline and not for a single second longer. So, there does seem to be something in cocoa that’s helping, but a few seconds here and there isn’t much to write home about. How about reversing the atherosclerosis, which we didn’t even think was even possible until 1977.

1977? Dean Ornish didn’t start publishing on heart disease reversal until 1979. In actuality, the first demonstration of atherosclerosis reversal with a cholesterol-lowering diet and drugs wasn’t on the coronary arteries going to the heart, but on the femoral arteries going to the legs.

What have researchers observed regarding the arteries going to the brain? There is a noninvasive way to measure arterial function within the brain using transcranial ultrasound. At 2:49 in my video, you can see a chart of what happens when we hold our breath. Once we start, our brain starts opening up the arteries to increase blood flow to compensate. If the arteries in our brain are stiffened and crippled by atherosclerosis, however, they’re unable to open as much and as fast as they should, and so are said to have a smaller “breath holding index,” which can be a risk factor for stroke. So, researchers designed an experiment in which they compared the results of a target food to something neutral, like oatmeal. What target food did they choose? A spoonful of cocoa powder or something? No. They chose a randomized crossover trial of oatmeal versus a deep-fried Mars bar.

Why a deep-fried Mars bar? The study was published in the Scottish Medical Journal, and, evidently, the “deep-fried Mars bar (DFMB) is a snack…strongly associate[d] with Scotland.” Really? Yes, really. Researchers phoned a total of 627 fish and chips shops in Scotland “to ascertain the delicacy’s availability.” More than one in five shops said they did carry deep-fried Mars bars and sold up to 200 a week. (Batter-dipped and deep-fried Snickers was evidently less popular.) The researchers “conclude[d] that Scotland’s deep-fried Mars bars is not just an urban myth. Encouragingly, [they] did also find some evidence of the penetrance of the Mediterranean diet into Scotland, albeit in the form of deep-fried pizza.”

Could this be contributing to Scotland having among the highest stroke rates in Europe?  Interestingly, there was a significant drop in men compared to women, which you can see at 4:29 in my video. Maybe men are from Mars and women are from Snickers? Regardless, what about chocolate that’s not deep-fried? There have been a few population studies that have followed people over time that found that those who ate chocolate appeared to have lower stroke rates, which has since been confirmed by another study. Is it possible, though, that chocolate consumption just happens to be related to other behaviors that are heart- and brain-healthy? Maybe people who exercise a lot have to eat more food, so maybe they eat more chocolate? Researchers didn’t see any evidence of that, but you can’t account for everything. To prove cause and effect, people would need to be randomized into two groups, with half eating chocolate and the other half not, and then followed for a decade or two. To this, one researcher replied that “it would be hard to gain consent from most people to the possibility of being randomized to a ‘no chocolate’ arm. How many people would agree to forego chocolate for a ‘sufficiently long follow-up period’?” Ten to twenty years without chocolate is a pretty long time.

Want more chocolate? See:

For more on stroke prevention, check out:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:



Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.

31 responses to “Dark Chocolate Put to the Test for Peripheral Artery Disease

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  1. I might stick with cocoa, thanks

    ‘During follow-up, 314 men died, 152 of cardiovascular diseases. Compared with the lowest tertile of cocoa intake, the adjusted relative risk for men in the highest tertile was 0.50 (95% CI, 0.32-0.78; P = .004 for trend) for cardiovascular mortality and 0.53 (95% CI, 0.39-0.72; P < .001) for all-cause mortality.

    Conclusion: In a cohort of elderly men, cocoa intake is inversely associated with blood pressure and 15-year cardiovascular and all-cause mortality.'

    1. I like a tablespoon of raw cacao in my morning coffee, along with turmeric, cinnamon and cardamon. Gives me energy for a workout.
      On a cold snowy day, after shoveling, I make cocoa. Almond milk, cinnamon, turmeric, and the cacao with a teaspoon of blackstrap molasses.
      Try making your own cocoa with plant milk and as little sweetener as possible. Easy to find raw cacao now, noticed even Costco has it.

      1. Marilyn Kaye, thank you for that very helpful information. Do you prefer using almond milk vs. soy milk? I once read that soy milk makes hot cocoa taste better than almond milk. Thoughts?

        1. Lucy, I use almond milk as I eat a lot of soy protein in other forms, edamame, black soy beans, tempeh. Also don’t particularly like the taste of soy milk. Just personal preference.

      2. I just use water to make cocoa (and oatmeal). Sweeteners and milks spoil the taste for me – as they do with tea and coffee – although adding beetroot powder to cacao and coffee can make stronger brews a little sweeter and less ‘bitter’.

  2. I watched the video again and laughed.

    I loved the Dr. Greger popping in the screen to give the “Maybe men are from Mars and women are from Snickers?” line.

    One of my favorite moments.

    1. Dr. Greger,

      Yesterday, Barb talked about not wanting people to give you 12 weeks of feedback and I know that I have been trying to give very detailed feedback because I know that you are in the evaluating what went wrong phase, but I even do like the newer video format, and I will be happy no matter what format.

      I used to sit next to film students plural and give feedback and that is why I decided to try to help. That’s all.

      1. Before then, I used to sit next to artists and writing groups and give feedback.

        Yes, I was the backseat driver giving feedback before that.

        1. Deb, after puzzling over many of your posts I can’t help but wonder what exactly is your job? And what were your jobs in the past? Hope it’s not intrusive to ask but you have thrown out so many interesting hints which I cannot figure out.

      2. Well Deb, yes I mentioned it but people can say /do whatever they feel they need to say. I just thought (my personal view here) that after 1 week, the criticisms were becoming very repetitive, and that we could move on to other subjects and allow NF to work it out. Here it is 6 or 8 weeks later, and still criticism is flowing and nothing unique is being added. I just don’t understand people’s thinking in this.

        Anyway, doesn’t matter. I am enjoying checking out some of the new topic sections NF has created like Fasting, and Athletes etc. It’s all good.

  3. ConsumerLab recently published testing results showing that most dark chocolate and cocoa powder contains unacceptable levels of cadmium. It seems that, for most brands, the cadmium content far surpassed the flavonal concentrations. I wonder how that plays into the health-promoting effects of chocolate/cocoa.

    1. ConsumerLab recently published testing results showing that most dark chocolate and cocoa powder contains unacceptable levels of cadmium.
      Its not like they are trying to hide that… at every easter they use the Cadmium Bunny to advertise chocolate easter eggs. ‘-)

      (Oh wait… I think I confused cadmium with the Cadbury Bunny.)

  4. I don’t care for chocolate really so going 20 yrs without would not be such a big deal. Hot chocolate without the marshmallows isn’t worth the time or trouble imo (or the cadmium, lead etc that comes with it).

    The study Fumbles cites is interesting for sure, but is it just a reflection of how poor diets can be on average in an elderly population? It’s absolutely shocking how badly the community around me is eating, so I can well imagine that antioxidants from cocoa powder would give them a boost.

  5. I occasionally drink organic raw cacao powder but for the most part I’ll pinch off a piece of unsweetened 100% cacao baking chocolate and eat that along with a few 60% cacao bittersweet chocolate chips to take some of the bitter edge off the baking chocolate.

    I may do this five or more times per day, but especially at night before going to bed since learning that a higher percentage of heart problems occur during the night or early morning.

    I also do not worry during the day about eating the bittersweet chocolate chips after learning and practicing the regimen below.

  6. Dr. Greger, should we be concerned about the caffeine in chocolate? I sometimes have heart palpitations, so that is my concern (even though I don’t intake any caffeine). I sometimes have blood pressure spikes, so I would be delighted to eat dark chocolate for that!

    1. Andrea, try to get enough magnesium in your diet. Often cures heart palpitations.
      Another thing is making sure you get enough exercise. Walking, at minimum, is very important in improving cardiovascular function.
      If you are not used to exercise, start slow, like 10-15 minutes. Work up till you can walk for 45 min. at a good pace at least 4-5x a week.
      Have seen patients on drugs for this, but they had stopped the drugs due to the side effects.
      A better diet, fruits and veggies, greens -and exercise- and palpitations usually disappear.

  7. I have come across articles that raise concern about heavy metal exposure associated with regular cocoa/cacao consumption, specifically cadmium (also mentioned are lead and nickel). Does anyone (especially Dr Greger) have an opinion on this? I enjoy 2 heaping tablespoons of cacao powder with date sugar, walnuts and banana mild on an almost daily basis, but the heavy metal issue is giving me pause. Please opine!

    1. I’d suggest that ‘2 heaping tablespoons’ is too much ….. as is ‘every day’.

      Most cacao/cocoa powders exceed the WHO limit for cadmium. Eating a high fibre diet can inhibit cadmium absorption I understand but then cadmium levels are higher in bran anyway so you may still be getting too much.

      i’d suggest just one (unheaped) spoonful every two or three days instead. Or even less often. As Berkely notes

      ‘The best way to get an array of antioxidant phy­tochemicals on a daily basis—including ones similar to those in cocoa and choco­late—is by eating a variety of fruits and vegetables. They have fewer calories than chocolate and an abundance of vitamins and minerals, along with fiber and other healthful plant compounds.’

      Although it also says ‘Just a small square a day [of dark chocolate] may be enough to satisfy, while minimizing the risk of heavy metals.’

      Personally, I prefer drinking cacao/cocoa and just use a teaspoonful and boiling water to make a drink every two or three days.

      That’s my two penneth anyway.

      How the trade-off between the good things in cacao vs the bad things in cacao plays out in the long run is difficult to estimate. Some other metals//minerals such as zinc, selenium and calcium are cadmium ‘antagonists’ for example so our overall diet can clearly affect uptake. However, I’d prefer to avoid high cadmium intakes in the first place rather than complicated dietary plans and/or zinc supplements for example.

  8. I would think that the HIGH levels of fat in chocolate would totally counteract any benefits. This is rediculous to not state this. Chocolate is very high in fat that clogs your arteries and veins.

    1. Chocolate is very high in fat that clogs your arteries and veins.
      Dark chocolate coats the inside of your arteries and veins with nitric oxide… that protects your blood vessels from deposition.

      Not only that, by producing Nitric Oxide, your vessels dilate and this action keeps your blood vessels supple and protects against hardening.

  9. VK,

    A few thoughts….. please note that the key to some extent is the amount consumed. If you re-read the suggested intake, “natural cocoa powder can be a health food.” was suggested. At 4:07 in Dr. Greger’s video he does voice concern with fat and sugar in chocolate products.

    There are benefits with a high level of cocoa solids and the consumption of small amounts daily, shown via the non-invasive studies and the longer-term lowered levels of stroke. ( also consider an animal study post stroke,

    Overall the best approach is the least fatty, lowest sugar format of cocoa or a very high percentage of dark chocolate in moderation. Please see for some suggestions.

    Dr. Alan Kadish moderator for Dr. Greger

  10. I often re-create these as handouts for my nutrition classes. It would be so nice if you could add a “download pdf” tab on the page. That would make it so much easier to share this valuabe information

  11. The famous French woman who lived to 122+ years old ate about one kilo of chocolate per week( that’s about 4 ounces per day) (in this description of her habits, no inference of any health effects was implied, and that’s the way it was phrased ” one kilo a week, ” , it said. ) Also, it said she smoked one cigarette a day.
    So, coincidentally, my wife eats about 4 heaping tablespoons of undutched dark cocoa powder (organic) per day, and has done so for many years. Recently, her blood pressure tested at the doctors office as normal for
    an average 28 year old woman, and she’s 70. Maybe dark cocoa is even more beneficial than we scientifically know about.

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