In an interesting New York Times piece, Murray Carpenter describes a 1911 case that anticipated the recent fuss over caffeine in energy drinks: The USDA's Bureau of Chemistry, predecessor to the Food and Drug Administration, sued the Coca-Cola Company, arguing that its famous soft drink was "adulterated" because it contained caffeine. Back then, Carpenter writes, Coca-Cola "contained as much caffeine as a modern Red Bull—80 milligrams per serving." He does not mention that it also contained another stimulant: cocaine, which was not completely removed until 1929, when the company began using decocainized coca leaf extract in its recipe. Perhaps the government's focus on caffeine can be explained by the relative doses of the two drugs, both of which were legal at the time. But it may also have been due to a bias against "artificial" ingredients: The cocaine was a natural constituent of coca leaf, whereas the caffeine was added in isolated form.
A similar bias seems to motivate critics of energy drinks such as Red Bull and Rockstar, which contain twice as much caffeine per ounce as modern-day Coca-Cola (which is down to 35 mg per 12-ounce serving) but about half as much as drip coffee. "How much caffeine is too much?" Carpenter asks toward the end of his article. "Is it different when added to soft drinks than as a natural constituent of coffee?" It is different in terms of the reaction it elicits from caffeine alarmists, but there does not seem to be any rational basis for this distinction.