Newsletter #321: Impact of Chocolate on Cardiometabolic Health 🫀
Chocolate attracts a lot of hype in health circles. A good deal of this is probably unmerited, or at least overblown.
And let's be honest, it probably reflects bias due to its hedonic properties. Chocolate has been held in high esteem for millennia. Indeed, the name of the genus to which the cocoa tree belongs, Theobroma, is derived from the Greek words theo (god) and broma (drink). We all want to hear good things about our favorite foods.
Nevertheless, cocoa really does have some advantages, much of which are associated with its polyphenols, especially flavanols. A lot of edible plants contain flavanols, but cocoa really stands apart in this respect. Chemical analysis has shown that not only is cocoa rich in these bioactive compounds, it contains a wider range of different subtypes of flavanols, including the smaller catechins and epicatechins as well as the more complex procyanidins. That is why researchers have even suggested that cocoa should, in effect, be the standard against which other flavanol-rich foods are evaluated. It is also the reason why cocoa products, as well as dark chocolate, are so commonly tested in trials exploring the diverse health effects of these compounds.
Recently, Brazilian researchers performed a meta-analysis of dozens of trials that examined how cocoa affected cardiometabolic health — referring here to body composition, blood lipids, blood glucose, and blood pressure. This week, I'd like to take a look at this analysis, and what we might learn from it.
This Week’s Research Highlight
🍫 Cocoa consumption elicits improvements in the lipid profile, glycemic control, and blood pressure.
Researchers in São Paulo conducted a systematic review and meta-analysis of randomized controlled trials assessing the long-term effects of cocoa consumption on various cardiometabolic markers.
Specifically, the researchers zeroed in on interventions that administered either a cocoa extract supplement or a dark chocolate that contained at least 70% cocoa content. Affected variables of interest in this analysis included anthropometric measurements (weight, BMI, etc), blood lipids, glycemic profile, and blood pressure.
Through their screening process, they identified 31 trials, enrolling a total of 1986 participants, which met their criteria, and extracted and analyzed the data from the studies.
Let's start with the (sort of) bad news: the anthropometric data.
Cocoa consumption showed no significant effects on body weight, BMI, or waist circumference. This finding might sound sort of, well, obvious (most people probably don't believe chocolate is likely to be much of an aid with respect to weight loss), but there is a compelling reason why trials examined this particular question. Cocoa is an abundant source of catechins — in fact, one of the richest among common foods. Catechins are a type of flavanol which has been shown to be protective against weight gain in animal models, and to a lesser extent in human trials. The specific types of catechins found in cocoa don't appear to show a strong effect on body composition though.
Anyway, the results with respect to the other cardiometabolic markers were more promising, and worth going through one by one.
Blood cholesterol
In randomized trials, cocoa consumption reduced total cholesterol (mean of −8.35 mg/dL) as well as LDL cholesterol (mean of −9.47 mg/dL). It did not significantly affect either triglycerides or HDL cholesterol.
Now, this is a fairly modest decrease in blood cholesterol, of course, but even relatively small reductions in LDL, over a long enough time span, can result in substantially lower cardiovascular risk. This is most strongly illustrated through analyses that examine the effects of genetic variants that are linked to lower cholesterol levels — in other words, the lifetime impact of reduced exposure to LDL. These sorts of studies have shown that a reduction in LDL of ~38 mg/dL is associated with more than 50% decreased risk of developing coronary heart disease.
It has been suggested that flavonoids in cocoa may lower LDL by inhibiting the absorption of cholesterol in the digestive tract, as well as boosting the expression of LDL receptors in the liver (basically, more LDL receptors in the liver to take up extra LDL means that there are fewer of those lipoproteins floating around in the bloodstream where they are liable to cause trouble).
Blood glucose
Cocoa consumption also elicited a reduction in fasting blood glucose (−4.91 mg/dL), although the impact of cocoa on blood sugar seems to have been largely confined to less healthy participants. Cocoa consumption did not, however, show a significant effect on HbA1c.
Preliminary evidence has suggested that cocoa polyphenols may improve insulin resistance, and intake of cocoa products has been linked to lower risk of developing type 2 diabetes in epidemiological studies (after controlling for sugar intake).
Incidentally, you might wonder why cocoa would improve fasting blood sugar but appear to not influence HbA1c. Well, HbA1c reflects longer term glycemic control. Alterations in glycated hemoglobin only emerge after around three months, due to the lifespan of red blood cells, so you wouldn’t expect to see much change in trials that only last 4-8 weeks. Accordingly, there was one intervention that showed a favorable effect of cocoa on HbA1c, and it happened to be the longest trial (24 weeks) in the meta-analysis. So, it’s reasonable to suppose that more trials of a sufficient duration might have found reductions in glycated hemoglobin.
Blood pressure
Finally, cocoa consumption led to significant decreases in both systolic blood pressure (−2.52 mmHg) and diastolic blood pressure (−1.58 mmHg). The impact was greater at higher polyphenol doses (reductions in systolic BP of −4.66 mmHg and diastolic BP of −2.68 mmHg).
Again, that may not sound like much, but it is a clinically meaningful magnitude of reduction. Prior research has revealed that a 4-5mmHg reduction in systolic blood pressure and a 2-3mmHg reduction in diastolic blood pressure can lower cardiovascular risk by 8-20%.
It is thought that flavanols in cocoa stimulate formation of nitric oxide in the walls of blood vessels, which causes them to widen and in turn lower blood pressure. We actually addressed this phenomenon in a study featured in an earlier newsletter, which found that a single dose of cocoa boosted blood flow in the legs and decreased systolic blood pressure.
In summary, cocoa is linked to a constellation of improvements in cardiometabolic biomarkers, which would be expected to translate to better health outcomes if sustained over time.
However, it's important to reiterate that these benefits appear to be tightly associated with the polyphenols naturally occurring in the cocoa. This means that if you are hoping to harness these benefits through chocolate, the most palatable choices may not be the most efficacious. For maximal polyphenol content, you have to select dark chocolate — the darker the better.
Random Trivia & Weird News
Military chocolate, issued to US personnel during WWII, was intentionally designed to not be tasty.
The US army commissioned chocolate bars for field rations in 1937. However, Hershey had to devise these bars quite differently from their usual confections.
First of all, they had to be built to withstand high temperatures, since they would potentially be carried outside in tropical climates. Secondly, the army insisted that these bars must taste "a little better than a boiled potato." This was to keep soldiers from gobbling up their emergency rations too soon. According to reports from men who tried to eat them, that objective seems to have been accomplished.
(Incidentally, the high cocoa content of the bar meant that it must have been very high in polyphenols, but I’m guessing that GIs did not appreciate these attributes at the time)
From Life Magazine
Podcasts We Loved This Week
- Marlou Lasschuijt: Eating rate, food texture, & satiation. Via Sigma Nutrition Radio.
- Ferris Jabr: From microbes to mammoths — How life transformed the planet. Via Science Friday.
Products We Like
CocoaVia
If you are trying to mirror the flavanol dosing used in studies like the ones analyzed, this product is probably the best option available. In fact, CocoaVia is actually the cocoa used in a lot of the research in this area! Each scoop of this powder contains 500 mg of cocoa flavanols with only 10 calories and virtually no cadmium (an all-too-common contaminant in cocoa products). They also offer capsules, but the powder is more cost-effective, and it’s not hard to use. I’ve added it to coffee successfully, and it also mixes well into smoothies and oatmeal. Adds a very rich chocolate flavor, not too bitter.
humanOS Catalog Feature of the Week
The How-to Guide to Ergogenic Aids
An ergogenic aid is simply a supplement that enhances physical performance. Intake of these substances can, in theory, affect training adaptations in a couple of different ways. They can achieve this by simply increasing the exercise stimulus from a single training bout — basically just enabling an athlete to train longer or harder — or by altering cellular responses to exercise-induced stress.
But it’s important to note that these changes in cell signaling may not be universally beneficial from the standpoint of adaptation. For example, it is theoretically possible that a supplement could simultaneously make it easier for an athlete to exercise hard while also having a long-term negative impact on the adaptive response to training.
In this guide, we review some of the most rigorously researched supplements, discuss how best to use them, and talk about why some supplements that sound like a good idea may actually not be helpful at all. If you are looking for a quick reference sheet of the latest evidence-based guidance on supplements to maximize your performance and adaptations, check it out! 👀
Wishing you the best,
