Caffeine Jitters
Sales boost in energy drinks and deaths linked to the products make scientists and regulators worry about safe levels of the stimulant

When Matthew Penbross woke on a morning in August 2007—a day in which he’d be competing in motocross races near Port Macquarie, Australia—he wanted to be prepared. To improve his reaction speed on the start line, the 28-year-old began drinking Red Bull Energy Drinks soon after he rolled out of bed. All told, he would drink seven or eight of the caffeinated beverages within a seven-hour period.
After his second race that day, Penbross wasn’t feeling well. But despite some short-lived chest pains, he kept riding and went on to win a race in the afternoon. Twenty minutes after he crossed the last finish line of the day, though, his heart stopped.
Penbross had no family history of heart disease, and he regularly drank a few Red Bulls per day, news reports later stated. The hospital doctors who treated his collapse and helped him recover went on to suggest that the excessive amount of caffeinated energy drinks he consumed was the likely culprit (Med. J. Aust.2009,190, 41).
Stories like Penbross’ have surfaced with increasing frequency in recent years. According to a report released last month by the U.S. Substance Abuse & Mental Health Services Administration, the annual number of emergency room visits associated with energy drinks increased to 20,000 in 2011, a 36% boost from the previous year. Late last year, the New York Times reported that the U.S. Food & Drug Administration is investigating reports of five deaths linked to Monster Energy drinks and 13 deaths linked to 5-Hour Energy shots.

CAFFEINE BY THE NUMBERS
Most beverages contain less caffeine than the recommended daily limit, but some are too caffeinated for pregnant women and children. a = Limit proposed by Health Canada. b= Limit proposed by U.K. Food Standards Agency. c = Average value. SOURCES: Consumer Reports, December 2012;

As concerns about the safety of these products have risen, so too have their sales. According to SymphonyIRI Group, a Chicago-based market research firm, the market for caffeinated energy drinks hit $9.8 billion last year.
“People often don’t understand the potential risk of these beverages,” says Bruce A. Goldberger, director of forensic toxicology at the University of Florida’s pathology labs. Caffeine is a stimulant and, when consumed at high enough levels, can have negative effects.
Monster Energy vigorously defends its safety record. In response to the fatality reports FDA is investigating, the company released the following statement: “Neither the science nor the facts support the allegations that have been made. Monster reiterates that its products are and have always been safe.” The firm also says a 16-oz can of its product contains only about half the caffeine found in a 16-oz cup of premium coffee, such as Starbucks.
Caffeine safety has proven hard to measure. Although scientists have established the toxic dose to be somewhere around 10 g, they say that the value can fluctuate depending on how a person processes the stimulant. Caffeine gets cleared from the body at different rates because of genetic variations, gender, and even whether a person is a smoker. For this reason, it’s difficult to set a safe limit of daily consumption on the compound. Physiological differences, as well as differences in the way people consume caffeine, have tied FDA in knots as it has debated how to regulate the substance.
Caffeine has long been prized for its ability to increase a person’s alertness and energy. According to lore, these properties were noted in the 9th century by an Ethiopian goatherd who found his flock frolicking after eating coffee berries from nearby bushes. What is not lore is that caffeine is one of the most frequently ingested pharmacological substances in the world. People proclaim their love of the chemical by displaying its structure on T-shirts, mugs, and