Tuesday, March 03, 2009
Chocolate and Your Health — Guilty Pleasure or Terrific Treat?
Fats. About a third of the fat in cocoa butter is oleic acid, the very same monounsaturated fat that gives olive oil its good name. Another third is stearic acid; it is a saturated fat, but unlike the three other saturated fats in the human diet, stearic acid does not raise cholesterol levels because the body can metabolize it to oleic acid. And while chocolate also contains some palmitic acid, a saturated fat that does boost cholesterol, careful studies show that eating chocolate does not raise blood cholesterol levels.
Flavonoids. The humble cacao bean contains a number of chemicals in the flavonoid family. Polyphenols protect chocolate from turning rancid, even without refrigeration. Even more important are the flavanols, a group of chemicals that are responsible for many of the protective actions of chocolate. Flavanols are present in many healthful foods—like apples, cherries, and black tea—but dark chocolate is the richest source.
Amino acids. Chocolate is high in tryptophan, phenylalanine, and tyrosine. Like other amino acids, these nitrogen-rich compounds are the building blocks of all the body’s proteins. But 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 postulate that dopamine induces feelings of pleasure. 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 tumors, which are rare.
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.”
From lab to lifeInternational experiments 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 antiplatelet 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 of 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.
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’d pack in more than 500 extra calories, enough to gain a pound a week.
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 elsewhere to keep your weight in line.
For more information about how food affects your health, order Special Health Report, Healthy Eating: A guide to the new nutrition, at www.health.harvard.edu/HE.
Labels: chocolate, cocoa, dark chocolate, flavonols, healthy food, oleic acid, polyphenols
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