The health benefits of chocolate are many. The key is to find a bar with high cocoa content. The higher the cocoa content, the less room there is for cocoa butter, sugar, lecithin, vanilla, milk, and other fillers.
Nutrition wise, chocolate is a champion antioxidant. Antioxidants help rid the body of free radicals - little molecules in your body which cause aging and disease. Antioxidants bond to free radicals and whisk them from your body via digestion and other means.
Remember hearing that red wine, green tea, pomegranates and blueberries are high in antioxidants? Dark chocolate leaves them all in the dust. The USDA published a chart of antioxidant foods measured in ORACs (Oxygen Radical Absorbance Capacity Units). For every 100 grams, dark chocolate has 13,120 ORACs, and blueberries have only 2,400!
Antioxidant-rich diets have been linked to a lowered risk of heart attacks, stroke, cardiovascular disease, cancer, high blood pressure, cholesterol problems, arthritis, asthma, Alzheimer's and more. So it stands to reason that if chocolate is chock full of antioxidants, it's actually good for you.
Cocoa butter, the main source of fat (besides milk) in chocolate, is composed of both saturated and unsaturated fats, but most of this, about 75%, is in the form of oleic and stearic acids. Diets rich in these acids have been shown to lower cholesterol levels. While 25% of the fat in chocolate is "the bad kind," the amount of good fat in chocolate seems to counteract the bad fat. And, as with all chocolates, the darker they are the less room there is for things like cocoa butter, and the more room for that healthy antioxidant-packed cocoa.
In regard to sugar, a strong dark chocolate bar might have ten to fifteen grams of sugar, which is still less than the 22 grams in your glass of orange juice! As for caffeine, an average bar contains about 27 mg, about half what you'd find in a cola and a third what you'd find in a cup of coffee.