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-dried 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:

 

In Late Pregnancy Moderate the Intake of Powerful Anti-inflammatory Foods

The right side of the heart pumps deoxygenated blood from the body to the lungs, where it can fill up with oxygen, and then the left side of the heart pumps oxygen-rich blood from the lungs to the rest of the body. So, blood travels from the body to the right side of the heart to the lungs to the left side of the heart and back to the body.

But what happens in the womb? Fetuses’ lungs don’t work because they’re filled with fluid. How does the heart bypass the lungs and spread the oxygen-rich blood coming in through the umbilical cord to the rest of the body? Before we’re born, we have an extra blood vessel—the ductus arteriosus—that directly connects the right side of the heart with the left side of the heart, bypassing the fluid-filled lungs. When the baby is born and takes a first breath, this blood vessel closes. In about 1 in 10,000 births, though, the blood vessel closes prematurely before the baby is born, necessitating an emergency C-section, as I discuss in my video Caution: Anti-inflammatory Foods in the Third Trimester.

Most cases for which there’s a known cause are thought to be related to taking anti-inflammatory drugs such as aspirin or ibuprofen. This is because the way the body keeps this blood vessel open is with a class of inflammatory compounds called prostaglandins. If you take an anti-inflammatory drug, you can undermine your body’s ability to keep it open, and it could constrict closed prematurely. That’s why most authorities recommend that these nonsteroidal anti-inflammatory drugs (NSAIDs) be avoided in the third trimester. The likelihood that anything bad will happen is extremely remote, but it’s better to be safe than sorry.

Sometimes this premature constriction happens even when women are not taking drugs, so-called “idiopathic” cases, which is doctorspeak for “we have no idea what causes it.” If anti-inflammatory drugs can cause it, though, what about anti-inflammatory foods? A few years ago, in my video Chamomile Tea May Not Be Safe During Pregnancy, I profiled two incidents apparently caused by pregnant women drinking chamomile tea. One of which reversed in that the ductus opened right back up once the tea was stopped, but, in the other case, the other baby had to come right out. Since then, there have been other case reports of this occurring––for example, when a woman had been drinking a few ounces of an acai berry drink every day and when another woman had been drinking prune juice and a violet vegetable juice containing a blend of fruits and veggies. Pregnant women should, therefore, take special care when consuming lots of these powerful anti-inflammatory berry nutrients.

What about berries themselves, green tea, and all the other wonderful anti-inflammatory foods and beverages out there? A group of researchers in Brazil compared ultrasounds of the hearts of third-trimester babies whose moms ate a lot of these anti-inflammatory foods with those whose moms ate less, and they could tell a difference. The speed of blood through the ductus in the moms consuming the anti-inflammatory diet was higher, suggesting it was narrower, just like when you pinch the opening of a hose closed and can make water shoot out faster. Also, the right sides of the hearts of the babies whose moms were consuming the anti-inflammatory diet were larger than their left sides, suggesting some blood backup, again an indicator of a tighter ductus. The researchers suggested changes in late pregnancy diets may be warranted, but critics replied that the differences they noted might not have any clinical relevance, meaning it may not matter if the vessel is a little more open or closed. We don’t want to alarm women because many of these anti-inflammatory foods may be beneficial––such as cranberries, for example, which may be useful in preventing urinary tract infections, which can be a risk factor for premature birth. Consuming cranberries is attractive from a public health and cost standpoint if it can prevent some premature births.

Before cutting down on a healthy food such as cranberries, we’d want some stronger evidence that they’re potentially harmful. What about confounding factors? For example, women who ate lots of anti-inflammatory foods might have had other characteristics that could affect fetal blood flow. What we needed was an interventional trial in which pregnant women change their diets and see what happens, but we didn’t have such studies… until now.

A study has shown that cutting back on anti-inflammatory foods such as tea, coffee, dark chocolate, grapes, and citrus for a few weeks during the third trimester did indeed seem to open up the ductus during normal pregnancies. In women whose fetuses had abnormally constricted vessels, a few weeks of eliminating polyphenol-rich foods reversed the ductal constriction in 96% of cases. Importantly, researchers didn’t follow these babies after birth to see if it made any difference. That complete closure only happens in 1 in 10,000 births; we’re not sure what effects relative levels of constriction may have, so it’s too early to be instituting a ban on dark chocolate for pregnant women.

At this stage, what we’re left with is a note of caution. During the rest of your life, I recommend eating healthy foods such as berries and cocoa powder, but from about 28 weeks until birth, pregnant women may want to cut back until we know more.


In Chamomile Tea May Not Be Safe During Pregnancy, I profile those two case reports I mentioned above. As I noted in Anti-inflammatory Antioxidants, highly antioxidant foods are, in general, highly anti-inflammatory foods.

For comparisons between the strength of anti-inflammatory foods and drugs, see Watermelon for Sore Muscle Relief, Anti-inflammatory Life Is a Bowl of Cherries, and Which Spices Fight Inflammation?

The videos provide more information about healthy (and unhealthy) diets in pregnancy:

In health,

Michael Greger, M.D.

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

Chocolate is Finally Put to the Test

Botanically speaking, seeds are small embryonic plants—the whole plant stuffed into a tiny seed and surrounded by an outer layer packed with vitamins, minerals, and phytochemicals to protect the seedling plant’s DNA from free radicals. No wonder they’re so healthy. By seeds, using the formal definition, we’re talking all whole grains; grains are seeds—you plant them and they grow. Nuts are just dry fruits with one or two seeds. Legumes (beans, peas, and lentils) are seeds, too, as are cocoa and coffee beans. So, finding health-promoting effects in something like cocoa or coffee should not be all that surprising. There is substantial evidence that increased consumption of all these little plants is associated with lower risk of cardiovascular disease.

Of course, much of chocolate research is just on how to get consumers to eat more. While it didn’t seem to matter what kind of music people were listening to when it came to the flavor intensity, pleasantness, or texture of a bell pepper, people liked chocolate more when listening to jazz than classical, rock, or hip hop. Why is this important? So food industries can “integrate specific musical stimuli” in order to maximize their profits. For example, purveyors may play jazz in the background to increase consumers’ acceptance of their chocolates. Along these lines, another study demonstrated that people rated the oyster eaten “more pleasant in the presence of the ‘sound of the sea’ than in the presence of ‘farmyard noises.’”

You’d think chocolate would just sell itself, given that it’s considered the most commonly craved food in the world. The same degree of interest doesn’t seem to exist as to whether or not Brussels sprouts might provide similar cardiovascular protection. So, it’s understandable to hope chocolate provides health benefits. Meanwhile, despite their known benefits, Brussels sprouts don’t get the love they deserve.

One of the potential downsides of chocolate is weight gain, which is the subject of my Does Chocolate Cause Weight Gain? video. Though cocoa hardly has any calories, chocolate is one of the most calorie-dense foods. For example: A hundred calories of chocolate is less than a quarter of a bar, compared to a hundred calories of strawberries, which is more than two cups..

A few years ago, a study funded by the National Confectioners Association—an organization that, among other things, runs the website voteforcandy.com—reported that Americans who eat chocolate weigh, on average, four pounds less than those who don’t. But maybe chocolate-eaters exercise more or eat more fruits and vegetables. The researchers didn’t control for any of that.

The findings of a more recent study published in the Archives of Internal Medicine were less easy to dismiss and there were no apparent ties to Big Chocolate. The researchers reported that out of a thousand men and women they studied in San Diego, those who frequently consumed chocolate had a lower BMI—actually weighed less—than those who ate chocolate less often. And this was even after adjusting for physical activity and diet quality. But, it was a cross-sectional study, meaning a snapshot in time, so you can’t prove cause and effect. Maybe not eating chocolate leads to being fatter, or maybe being fatter leads to not eating chocolate. Maybe people who are overweight are trying to cut down on sweets. What we need is a study in which people are followed over time.

There was no such prospective study, until now. More than 10,000 people were followed for six years, and a chocolate habit was associated with long-term weight gain in a dose-response manner. This means the greatest weight gain over time was seen in those with the highest frequency of chocolate intake. It appears the reason the cross-sectional studies found the opposite is that subjects diagnosed with obesity-related illnesses tended to reduce their intake of things like chocolate in an attempt to improve their prognosis. This explains why heavier people may, on average, eat less chocolate.

To bolster this finding came the strongest type of evidence—an interventional trial—in which you split people up into two groups and change half their diets. Indeed, adding four squares of chocolate to peoples’ daily diets does appear to add a few pounds.

So, what do we tell our patients? In 2013, researchers wrote in the American Family Physician journal that “because many cocoa products are high in sugar and saturated fat, family physicians should refrain from recommending cocoa….” That’s a little patronizing, though. You can get the benefits of chocolate without any sugar or fat by adding cocoa powder to a smoothie, for example. Too often, doctors think patients can’t handle the truth. Case in point: If your patients inquire, one medical journal editorial suggest, ask them what type of chocolate they prefer. If they respond with milk chocolate, then it is best to answer that it is not good for them. If the answer is dark chocolate, then you can lay out the evidence.


Even better than dark chocolate would be cocoa powder, which contains the phytonutrients without the saturated fat. I’ve happily (and deliciously) created other videos on cocoa and chocolate, so check out Update on Chocolate, Healthiest Chocolate Fix, A Treatment for Chronic Fatigue Syndrome, and Dark Chocolate and Artery Function. 

Whether with Big Candy, Big Chocolate, or some other player, you always have to be careful about conflict of interest. For more information, watch my Food Industry Funded Research Bias video.

In health,

Michael Greger, M.D.

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