As the beverage market has exploded, so have the claims about metabolic benefits. Here's a look at the main boosts being boasted.
Photo: Nigel Cox
Caffeine is the key ingredient, sometimes from ingredients such as guarana, cacao, or mate. Not an energy source per se, but a nervous-system stimulant that does provide a short-term boost. If the amount of caffeine is listed, here's a reference: An 8-ounce cup of coffee has about 150mg.