Chocolate: Divine food, devilish temptation

It all began with the cacao tree, which originated in Central America more than 4,000 years ago and has been cultivated by humans for more than 1,000 years. The Aztecs and the Mayans believed that the cacao was a divine gift from paradise. Both groups used cacao in religion and commerce.Cortez brought cacao beans to Spain in the early 16th century. The Spaniards added sugar and cinnamon to the bitter Indian drink, and the rest is history.

Chocolate chemistry

The cacao bean contains more than 400 chemicals. Many of them can affect human biology and health.

• Fats. Cocoa butter is high in fat. It’s what gives chocolate its tempting texture and “mouth feel”  but it’s also what gives chocolate its bad name. Although it’s true that chocolate fat packs a lot of calories, it’s not guilty of the charge that it raises blood cholesterol levels.

• Flavonoids. The cacao bean contains a number of chemicals in the flavonoid family. Probably the most important are the flavanols, a group of chemicals that’s responsible for many of the protective action of chocolate. Flavanols are present in many healthful foods, but dark chocolate is the richest source. (see table).

• Amino acids. Chocolate is high in tryptophan, phenylalanine, and tyrosine. Two of these amino acids have a unique property: They are precursors of adrenaline, a “stress hormone,” and dopamine, a neurotransmitter that relays signals between nerve cells in the brain. Scientists speculate that dopamine induces feelings of pleasure. If so, the passionate craving of the true chocoholic may have a neurochemical basis. But these chemicals may also explain some of the adverse effects of chocolate, including its ability to trigger headaches in some migraine sufferers, its ability to raise blood pressure to dangerous levels in some patients taking monoamine oxidase inhibitors for depression, and its ability to instigate diarrhea, wheezing, and flushing in patients with carcinoid syndrome.

• Methylxanthine. Chocolate contains two members of this group of chemicals. One is obscure, the other notorious, but both theobromine and caffeine have similar effects on the body. They may explain why chocolate makes some hearts beat faster  and why it gives many people heartburn by relaxing the muscle between the stomach and the esophagus, thus allowing acid to reflux up from the stomach into the sensitive “food pipe.”

Sweet science

The flavonoids have many properties that might improve health. Thus, it’s no surprise that chocolate has attracted the interest of scientists from around the world, giving the research an international flavor. Most studies concentrate on aspects of cardiovascular health. Here are some representative findings:

• Antioxidant activity. Antioxidants protect body tissues from damage by oxygen free radicals. Here are two studies: Scientists from Italy and Scotland fed dark chocolate, milk chocolate, or dark chocolate and whole milk, to healthy volunteers. Dark chocolate boosted blood antioxidant activity but milk, either in the chocolate or in the glass, prevented the effect. Similarly, researchers in Finland and Japan found that dark chocolate reduces LDL oxidation while actually increasing levels of HDL (“good”) cholesterol, but white chocolate lacks both benefits.

• Endothelial function. The endothelium is the thin inner layer of arteries. It’s responsible for producing nitric oxide, a tiny chemical that widens blood vessels and keeps their linings smooth. Can chocolate help? Doctors in Greece think it may. They fed 100 grams of dark chocolate to 17 healthy volunteers and observed rapid improvement in endothelial function. Swiss investigators found similar effects from dark chocolate but no benefit from white chocolate. German scientists report that flavanol-rich cocoa can reverse the endothelial dysfunction produced by smoking, and European doctors reveal that dark chocolate appears to improve coronary artery function in heart transplant patients.

• Blood pressure. Because good endothelial function widens blood vessels, it’s logical that chocolate might help lower blood pressure. Studies from Italy, Argentina, Germany, and the US show that dark chocolate can lower blood pressure in healthy adults and in patients with hypertension. A 2007 meta-analysis of five trials, however, found that the effect is modest, lowering both the systolic and diastolic pressure by just five millimeters of mercury (mmHg). The benefit wears off within a few days after eating chocolate.

• Insulin sensitivity. Chocolate is the food that diabetics love to hate, and the sugar and calories give them good reason to eschew it. But an Italian study in nondiabetics suggested that dark, but not white, chocolate can improve insulin sensitivity. However, a small 2008 investigation of flavonol-enriched cocoa in diabetics found no improvement in blood sugar control or blood pressure.

• Blood clotting. Most heart attacks and many strokes are caused by blood clots that form on cholesterol-laden plaques in critical arteries. These clots are triggered by platelets; the anti-platelet activity of aspirin explains its important role in patients with coronary artery disease. Researchers in Switzerland and the US found that dark chocolate reduced platelet activation.

From research to reality

Indeed, international researches show that dark chocolate has an impressive array of activities: it is an antioxidant that may improve your cholesterol; it improves endothelial function and may lower your blood pressure; it is a sweet that may lower your blood sugar; and its anti-platelet activities could reduce your chances of developing an artery-blocking clot. Taken together, these properties could reduce the risk of heart attack and stroke. But all these hopeful results are based on short-term experiments in a small number of volunteers. Do these bits and pieces of data apply to real life? Perhaps. The most robust support for chocolate as an asset to health comes from a 2006 report from the widely respected Zutphen Elderly Study. Researchers evaluated 470 Dutch men between the ages 65 and 84; all were free of diabetes, cardiovascular disease, and cancer when the study began in 1985. Each volunteer provided comprehensive dietary information, and each underwent a detailed evaluation of his blood pressure, cholesterol, body fat, and other cardiovascular risk factors.Researchers tracked the men for 15 years. They found that the men who ate the most cocoa-containing products had lower blood pressures than those who ate the least; the average difference was 3.7 mmHg in systolic pressure and 2.1 mmHg in diastolic. Those differences may not seem substantial, but even after taking other risk factors into account, the chocolate lovers also enjoyed a 47-percent lower mortality rate; most of the benefits were explained by a sharply decreased risk of cardiovascular disease. And the largest single source of cocoa was dark chocolate.

Raising the bar

To the ancient Mayans, chocolate was the food of the gods. Many people today agree, but others fear death by chocolate, assuming that anything tasting so good must be bad for you. So, is chocolate divine food or a devilish temptation? New research suggests that chocolate may, indeed, have a role in promoting vascular health, but the devil is in the details. The first consideration is the type of chocolate. Dark chocolate appears beneficial, but milk chocolate, white chocolate, and other varieties do not. The second issue is calories. Most trials have used 100 grams of dark chocolate, the equivalent of eating about one-and-a-half chocolate bars of typical size. If you ate that much every day, you’ll pack in more than 500 extra calories, enough to gain a pound a week. And if that’s not bad enough, remember that chocolate can trigger migraines, heartburn, or kidney stones in susceptible people.If you’re a chocolate lover, choose dark chocolate; the first listed ingredient should be cocoa or chocolate liquor, not sugar. Limit yourself to a few ounces a day, and cut calories to keep your weight in line. Others feel a few treats a week may be just right. And don’t rely on chocolate to make up for a bad diet or insufficient exercise. But if you make dark chocolate a part of a healthy lifestyle, you can have the pleasure without the guilt. The key to exploiting chocolate benefits is to balance the health effects of flavonoids with the fats that make it such a calorie-dense food.But whatever experts say, romantics know that even a little bite of chocolate is enough to warm up a cold heart.