Is Cocoa in Your Pantry?

Chocolate Can Lower
Your Blood Pressure

Not to twist your arm or anything, but perhaps you
should consider making cocoa products a dietary staple
By Will Block

f a doctor ever tells you you have an idiopathic disease, don’t take offense—it does not mean that you’re some kind of idiot. In doctor-speak, idiopathic means “of unknown cause.” One medical dictionary defines the term, with admirable candor, as “a high-flown term to conceal ignorance.” Despite all its efforts, the medical profession is still, alas, ignorant of many important aspects of human health and disease.

Take hypertension (high blood pressure), for example. The cause of most cases of this disease—about 90% of all cases, actually—remains a mystery.* In such cases, the disease is called essential hypertension. Again, don’t be confused by the jargon. “Essential” in this case doesn’t mean “necessary” (as it does, e.g., in the term essential amino acid), but rather “of unknown cause”—idiopathic again. So why not call it idiopathic hypertension? Because that sounds a bit too high-flown, even for doctors.


*The other 10% of cases are attributed to such things as kidney disease, tumors of the adrenal glands, hyperthyroidism, malformation of the aorta, and drug interactions. Hypertension is also often a temporary “side effect” of pregnancy.


Speaking of high-flown, doctors often feel a kind of “high” when they’re able to prescribe some powerful or exotic medicine that can cure, or at least control, a patient’s disease. That is, without a doubt, a major accomplishment, bringing to fruition the long, hard years of their medical education and training—not to mention the unending research carried out by scientists at pharmaceutical companies. The “miracles” of modern medicine are, of course, not miracles at all, just the collective result of immense effort by innumerable talented people.

The Plant World Is a Living Treasure Chest

In the medical arena, however, Mother Nature is not to be outdone by us upstart humans. The evolution of life on earth has provided a staggering variety of plants that are rich in biologically active compounds of potential use to us as medicines. (The premier—but by no means only—source of such botanical treasures is the tropical rainforests.) About one-quarter of all prescription drugs have been derived from compounds found in plants, yet we have barely scratched that surface: fewer than 1% of the world’s plant species have been thoroughly investigated for their potential medicinal value.

Thus, we have much to look forward to, provided that we are smart enough to figure out how to protect and preserve the planet’s natural resources, especially the rainforests, without empowering the government as the only way to accomplish this goal. Equally important is that we try to learn as much as we can about natural medicine from the rainforests’ indigenous peoples, who are living repositories of arcane knowledge that could benefit our civilization.

The Cocoa Tree Is a Jewel in the Crown

So start figuring out how you can make a difference. Write a letter to the editor, preferably while nibbling on some chocolate as a reminder of why all this is so important. It’s just a lucky accident, of course, that the medicinal qualities of chocolate come in such a divinely delicious form, thereby guaranteeing that Theobroma cacao, the cocoa tree, will never make it onto the endangered species list. Life without chocolate? Unthinkable!

It is said that chocolate is the most craved of all foods on earth—and not just because it tastes so good. Chocolate contains a variety of psychoactive chemical compounds that make us feel good, including the “love molecule,” phenylethylamine, which is the precursor to an astonishing variety of other mood-altering compounds. (For more on phenylethylamine and why chocolate makes us both happier and healthier, see “Chocolate for Longer and Happier Life” in the May 2007 issue.)

Chocolate also contains minute quantities of a compound called anandamide (from ananda, the Sanskrit word for bliss), which, like phenylethylamine, occurs naturally in humans. Anandamide is a neurotransmitter whose effects are similar to those of the cannabinoids, a class of compounds found in marijuana (Cannabis sativa). Whether or not the amount of anandamide in chocolate is enough to improve our mood is unknown, but whatever its cause, a chocolate “high” is, in any case, both safe and legal.

You Want More? Try Cocoa Products

Getting back to earth, something in chocolate definitely improves our blood pressure, and that something is believed to be certain members of a class of polyphenolic compounds called flavonoids, especially two flavonoid subclasses called flavanols and proanthocyanidins (the latter are flavanol polymers). These highly beneficial compounds are found in cocoa solids but not in cocoa butter. That explains why dark chocolate (with the greatest amount of cocoa solids) provides the greatest health benefits, milk chocolate provides some benefits, and white chocolate (which contains no cocoa solids and is therefore not really chocolate) provides none.

These assertions are backed up by a growing body of scientific evidence, some of which was presented in the Life Enhancement article cited above and in a second one in the July 2007 issue entitled, “Should We Eat More Chocolate?” The answer to that question is yes (as if you needed to be told), but with the usual caution: in moderation, because of the fat and sugar that chocolate contains. As with many other things, if a little is good, a lot is not necessarily better—the tables can quickly be turned to the downside.

One of the beauties of chocolate, however, is that we can obtain its health benefits in another delicious way, namely, in the form of cocoa-based products that contain very little cocoa butter (fat). But wait, that still leaves the sugar, doesn’t it? It’s true that cocoa is bitter and must be sweetened to make it palatable, but it’s not necessary to use sugar. A good substitute is the nonsugar sweetener erythritol, which has only about one-tenth the calories of sugar. Voilà—minimal downside. Eat up!

German Chocolate, Anyone?

Most of the studies on chocolate’s ability to reduce blood pressure have been of very short duration—no more than 2 weeks. To address this problem, a research group in Germany conducted a randomized, controlled trial of 18 weeks’ duration.1 It involved 44 men and women, aged 55 to 75, who were in good general health except for having “upper-range prehypertension” (blood pressure between 130/85 and 139/89) or stage 1 hypertension (blood pressure between 140/90 and 160/100). Among the many health- and nutrition-related factors that could exclude someone from participating in this study were the use of nutritional supplements and the consumption of more than one serving per week of chocolate or other cocoa-containing products.

Half of the study participants (22) were given 6.3 g (0.22 oz) daily of a commercial dark chocolate bar (German, of course) that contained 3.1 g (49%) of cocoa solids, which, in turn, contained 30 mg of polyphenols (i.e., the polyphenol content of the cocoa was about 1%); each such piece contained 30 calories from the fat and sugar. The other 22 participants, serving as controls, received an equivalent amount of white chocolate (the “un-chocolate”) with the same caloric content. By the nature of dark vs. white, the participants could not be “blinded” to what they were taking, but procedures were followed to ensure that the investigators were blinded, thereby eliminating that potential for bias, at least. Thus the trial was single-blind, not double-blind.

Cocoa Suppresses Oxidized Cholesterol—But How?

Many things besides blood pressure can affect your cardiovascular health for better or worse. One of them is your levels of cholesterol, both the bad kind (LDL-cholesterol) and the good kind (HDL-cholesterol). Have trouble remembering which is which? Just remember that you want your LDL to be Lower and your HDL to be Higher. Simple!


© iStockphoto.com/Fred Shakeshaft/Mat Greiner
There’s nothing wrong with LDL-cholesterol per se. In fact, you could not live without it, so a certain amount of it in your blood is essential. Too much of it is harmful, however, especially if it becomes oxidized as a result of oxidative stress, the catchall term for the deleterious actions of reactive oxygen species, including free radicals. The problem with LDL-cholesterol that has become oxidized (or “peroxidized,” a fine distinction that only chemists care about) is that it contributes greatly to the formation of artery-clogging atherosclerotic plaque. Thus, anything that can help prevent such oxidation is beneficial.

Many natural substances fill that bill, and cocoa polyphenols are among them. During the last few years, a research group in Japan has demonstrated cocoa powder’s effectiveness in increasing the resistance of LDL-cholesterol to oxidation in both rabbits and humans; they also observed that cocoa made the humans’ LDL levels lower and their HDL levels higher—exactly what health-savvy humans want. These results were in agreement with those of several other research groups.

Now the same Japanese researchers have extended their studies by examining the effects of three different intakes of cocoa powder on plasma cholesterol levels and on the susceptibility of LDL-cholesterol to oxidation in healthy humans with normal or mildly elevated cholesterol levels.1 Using 160 volunteers, average age 49, they administered cocoa powder or placebo daily, as a beverage, for 4 weeks. The cocoa amounts used were 0 g (control group), 13 g, 19.5 g, and 26 g.

The results showed that cocoa produced small but significant reductions in LDL-cholesterol levels, especially in the hypercholesterolemic subjects, and somewhat larger increases in HDL-cholesterol levels in all the subjects; there were also substantial decreases in the levels of oxidized LDL-cholesterol in all the subjects. In almost all cases, the changes were dose-dependent, i.e., the greater the amount of cocoa used, the greater the effect.

It’s possible that the reduction in oxidized LDL-cholesterol was mainly the result of the reduction in LDL-cholesterol to begin with, but it’s also possible that it was caused, at least in part, by a protective effect of the cocoa polyphenols. It’s not known, however, whether this protective effect, if real, was due to an antioxidant action of the polyphenols (by scavenging free radicals, e.g.) or to some other biochemical mechanism that led to the same result.

In light of the mounting evidence that polyphenols are not antioxidants in vivo (see the accompanying article), it seems likely that some other explanation is needed. One such explanation is that the polyphenols’ protective action is due to their removal of potentially pro-oxidant transition-metal ions by chelation. Another is that the increases in HDL-cholesterol levels that they induce may contribute to a suppression of LDL-cholesterol oxidation. In truth, no one knows what the answer is. Whatever it is, though, we can be grateful for cocoa’s effect on our health.

Reference

  1. Baba S, Natsume M, Yasuda A, Nakamura Y, Tamura T, Osakabe N, Kanegae M, Kondo K. Plasma LDL and HDL cholesterol and oxidized LDL concentrations are altered in normo- and hypercholesterolemic humans after intake of different levels of cocoa powder. J Nutr 2007; 137:1436-41.

Chocolate Reduced Blood Pressure

The researchers measured the participants’ blood pressure at baseline and again at 6, 12, and 18 weeks. They also measured their plasma levels of two chemical compounds: (1) S-nitrosoglutathione, which serves as a marker for nitric oxide, a molecule that causes dilation of blood vessels and hence a reduction in blood pressure; and (2) 8-isoprostane, which serves as a marker for oxidative stress caused by the generation of reactive oxygen species, including free radicals.

Over the 18-week period, dark chocolate, but not white chocolate, caused a progressive decrease in blood pressure (BP) compared with baseline values: the final figures were 2.9 mmHg lower in systolic pressure (the higher of the two BP figures) and 1.9 mmHg lower in diastolic pressure (the lower figure). That might not sound like much, but the authors explained its significance as follows:1

Although the magnitude of the BP reduction was small, the effects are clinically noteworthy. On a population basis, it has been estimated that a 3-mmHg reduction in systolic BP would reduce the relative risk of stroke mortality by 8%, of coronary artery disease mortality by 5%, and of all-cause mortality by 4%.

Dark chocolate, but not white chocolate, also progressively increased the participants’ S-nitrosoglutathione levels. This confirmed what previous studies had suggested: the blood pressure-reducing effects of chocolate are apparently mediated by a chronic increase in the production of nitric oxide in the vascular endothelium, the layer of cells lining the inner walls of our blood vessels. This is believed to occur as a result of exposure of the vascular endothelium to the cocoa flavanols.

Surprise (?) — No Antioxidant Activity!

Finally, neither kind of chocolate had any effect on the participants’ 8-isoprostane levels. Since that compound is a reliable and specific marker for oxidative stress, this indicates a lack of antioxidant activity by the cocoa flavanols. That probably comes as a surprise to those who have long believed that flavanols—and other flavonoids, and polyphenols in general—are strong antioxidants.

Although it’s true that polyphenols are strong antioxidants in laboratory experiments, this is apparently not true in living organisms (in vivo), where it really counts. According to scientists at the Linus Pauling Institute, the antioxidant properties of flavonoids and other polyphenols are, in fact, minimal in vivo.* Research has indicated that other, more complicated mechanisms can explain the indisputable health benefits of these compounds.


*For more on this revelation, see the sidebar “Antioxidants: A Story of Blueberries and Red Herrings” in the July 2007 article mentioned above. But just to complicate matters, the sidebar to this article presents the results of a study suggesting that cocoa polyphenols may have some antioxidant activity in vivo. Nothing is simple.


Chocolate Is Good for Everyone

All of the above results, by the way, were no different between the men and the women in this study—chocolate was nonsexist in its actions. Also, the small amount of chocolate used had no significant effect on the participants’ weight, lipid profile, glucose metabolism, or insulin sensitivity. The authors cautioned that, owing to certain limitations of the study, their results “may be valid only for individuals who are older and mildly hypertensive but otherwise healthy.” However, they cited other studies indicating that cocoa products reduce blood pressure in younger individuals with or without hypertension (see the July 2007 article mentioned above).

They concluded with the following comment (literature citations omitted) containing a nice bit of understatement:1

The most intriguing finding of this study is that small amounts of commercial cocoa confectionary convey a similar BP-lowering potential compared with comprehensive dietary modifications that have proven efficacy to reduce cardiovascular event rate. Whereas long-term adherence to complex behavioral changes is often low and requires continuous counseling, adoption of small amounts of flavanol-rich cocoa into the habitual diet is a dietary modification that is easy to adhere to and therefore may be a promising behavioral approach to lower blood pressure in individuals with above-optimal blood pressure.

Easy to adhere to? You think? Gee, maybe it’s worth considering . . .

Reference

  1. Taubert D, Roesen R, Lehmann C, Jung N, Schömig E. Effects of low habitual cocoa intake on blood pressure and bioactive nitric oxide. JAMA 2007;298:49-60.


Will Block is the publisher and editorial director of Life Enhancement magazine.

FREE Subscription

  • You're just getting started! We have published thousands of scientific health articles. Stay updated and maintain your health.

    It's free to your e-mail inbox and you can unsubscribe at any time.
    Loading Indicator