The findings are published in September's issue of Consumer Reports, published by the non-profit group Consumers Union. The organization tested 12 carbonated energy drinks -nine regular and three low-calorie - for caffeine content and taste. Caffeine levels were found to range from 50 mg to 145 mg per 8 oz serving, as compared with the roughly 100 mg found in a cup of coffee. These results on one hand vindicate energy drink makers who have been blamed for over stimulating consumers with high caffeine and sugar content, but also point to issues relating to serving sizes as this category continues to drive sales in the functional beverage market. Over the past year, sales of energy drinks shot up by 34 percent, according to market research firm Information Resources, with Americans having spent $744mn on the beverages during the year ending June 2007. The category of energy drinks has in some ways been the successful black sheep of the functional food and beverage family. With dubious nutritional content, the drinks have been wildly popular as lifestyle accessories - with names like Rockstar, Full Throttle, and No Fear - geared at younger generations. While the term "energy drink" sounds healthful, says Consumer Reports, most of these drinks contain stimulants that are not healthy choices for young children and pregnant women, and can be risky if mixed with alcohol. And according to Mintel, more than one fourth of adult energy drink consumers do just that - combine energy drinks with their alcoholic beverage of choice. Manufacturers are currently not required to label the caffeine content of their products, so there is the fear consumers will overload on caffeine from different sources without realizing it. Most of the energy drinks tested by Consumer Reports came in cans or bottles larger than 8 oz. As such, after drinking an energy beverage, a consumer could have ingested up to 200 mg of caffeine and 260 calories. A 12 oz can of Coke by contrast contains about 24 mg of caffeine. Acceptable caffeine intake for adults is said to be about 300 mg per day, whereas it is under 100 mg for children. Therefore, one energy drink puts a child well over their daily limit. From Cocaine to Enviga, energy drinks have had their share of controversy. In the fall of the 2006, Coca-Cola and Nestlé launched the carbonated green tea energy drink Enviga, with claims the beverage burns more calories than it provides. In February, Lawsuits were filed by consumer group Center for Science in the Public Interest (CSPI) against both companies. Around the same time, Redux Beverages also unveiled the energy drink whose name would bring it notoriety: Cocaine. The company was subsequently forced to stop distributing and marketing the beverage following the threat of action from the US Food & Drug Administration (FDA) and other government branches. Las Vegas-based Redux looks set to choose a new name for its energy product.