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:

 

Best Foods for COPD and Peripheral Artery Disease

It’s great we can improve athletic performance by eating a few beets, but so what if you run 5% faster? It can be a fun experiment to eat a can of beets and maybe shave a minute off your 5k time, but there are people who could really benefit from a more efficient use of oxygen: those suffering from emphysema. Young, healthy adults eating greens and beets can swim, run, and cycle faster and farther, but what about those who get out of breath just walking up the stairs? Do nitrate-rich vegetables work where it counts? Yes–. Time on the treadmill in COPD pateints was significantly extended after two shots of beet juice. I discuss these benefits of nitrate-rich vegetables in my video Oxygenating Blood with Nitrate-Rich Vegetables.

Beet juice can also decrease blood pressure in young, healthy adults, but what about in those who need it––older, overweight subjects? Just one shot a day of beet juice (versus berry juice as a control) led to a significant drop in blood pressure in a few weeks. But within just a few days after stopping three weeks of beeting themselves up, blood pressure went back up. So we have to eat our vegetables and keep eating our vegetables.

Why did it take until 2015 to publish a study on using nitrates to lower blood pressure in people with high blood pressure? You’d think that’d be the first group to try it on. Who’s going to fund it, though—Big Beet? Blood pressure medications rake in more than $10 billion a year. You can’t make billions on beets.

But that’s why we have charities like the British Heart Foundation, which funded a study to give folks with high blood pressure a cup of beet juice a day for four weeks. After all, high blood pressure may be the number-one risk factor for premature death in the world. In ten years, it could affect nearly one in three adults on the planet. But put them on beet juice and blood pressures dropped and kept dropping until they stopped drinking it after a month. With so many people with high blood pressure even despite treatment, the researchers concluded, “an additional strategy, based on the intake of nitrate-rich vegetables, may prove to be both cost-effective, affordable, and favorable for a public health approach to hypertension.”

What about those with peripheral artery disease? There are tens of millions of people with atherosclerotic clogs impairing blood flow to their legs. This can cause a cramping pain in the calves called claudication, due to lack of blood flow through the blocked arteries, severely limiting one’s ability to even just walk around. But when they simply drink some beet juice, they can walk 18% longer. Researchers measured the actual oxygenation of blood within the calf muscle and found that patients were able to maintain more oxygen in their muscles after drinking beet juice.

The nitric oxide from vegetable nitrates not only improves oxygen efficiency but also oxygen delivery by vasodilating blood vessels—opening up arteries—so there’s more blood flow. I’m surprised beet juice companies aren’t trying to position themselves as veggie Viagra! It could certainly explain why those eating more veggies have such improved sexual function, though that study was a snapshot in time so technically you can’t tell whether eating veggies resulted in improved sexual function or improved sexual function led to eating more veggies. However, it seems more reasonable that low fruit and vegetable consumption contributes to erectile dysfunction, rather than the other way around.

What about the most important organ… the brain? Poor cerebral perfusion—lack of blood flow and oxygen in the brain––is associated with cognitive decline and dementia. Researchers showed that the nitrate in vegetables may be beneficial in treating age-related cognitive decline. They showed a direct effect of dietary nitrate on cerebral blood flow within the frontal lobes, the areas particularly compromised by aging. This is a critical brain area for so-called executive function, the basic task and problem solving important for day-to-day functioning. The nitrite from nitrate has been shown to not only increase blood flow to certain areas of the body but also to act preferentially in low oxygen conditions, allowing it to increase blood flow precisely in the areas where it is needed most, and that’s what they found in the brain: increased blood flow to the at-risk areas of the aging brain. The only side effect of beeting your brains out? A little extra color in your life (they noted some of the study subjects started peeing pink).


Nitrates are one of the reasons I recommend eating dark green leafy vegetables every day. See Slowing Our Metabolism with Nitrate-Rich Vegetables and “Veg-Table” Dietary Nitrate Scoring Method. Beets are another good option and not just drinking the juice; take a look at Whole Beets vs. Juice for Improving Athletic Performance.

What else can we do for high blood pressure? See the following videos:

Why is blood flow to the brain so important? I go into depth on the potential consequences in Alzheimer’s and Atherosclerosis of the Brain.

More on diet and pelvic blood flow in men can be found in:

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: