The New York attorney general has subpoenaed three large makers of so-called energy drinks as part of an investigation into whether the companies are misleading consumers about how much caffeine the drinks contain and the health risks they could pose.
The attorney general, Eric T. Schneiderman, is also looking at whether the companies — Monster Beverage, PepsiCo and Living Essentials — violated federal law in promoting the drinks as dietary supplements rather than as foods, which are regulated more strictly.
State authorities are also concerned about whether all of the ingredients that go into the beverages are properly disclosed, according to an official briefed on the investigation who spoke on the condition of anonymity.
The state investigators are also examining whether some additives, like black tea extract and guarana, may contain additional caffeine that is not reflected when the drinks are labeled.
The subpoenas were issued in July, and the official said more companies could face requests for information as the investigation progresses.
Besides Monster’s drink, the beverages under state scrutiny are AMP from Pepsi and 5-hour Energy drink, which is made by Living Essentials.
Living Essentials reported that a state attorney general inquiry was under way last month during a bond offering, but a spokeswoman declined to comment further on Tuesday. Spokesmen for Monster and Pepsi also declined to discuss the subpoenas.
The investigation was reported on Tuesday by The Wall Street Journal.
In a statement, the American Beverage Association said it could not comment on the details of the investigation by Mr. Schneiderman. The trade association statement noted that ingredients and labeling for energy drinks were regulated by the Food and Drug Administration and that caffeine levels from additives were fully disclosed. It also said that the industry had voluntarily restricted marketing to children and the sale of energy drinks in schools.
In 2010, the F.D.A. issued warning letters to four companies that made energy drinks combining alcohol and caffeine — Charge Beverages, New Century Brewing, Phusion Projects and United Brands — citing a health risk. Despite concerns by public health experts, the F.D.A. has not taken on makers of more traditional energy drinks, which are often carbonated and provide a quick, caffeine-fueled boost.
Energy drinks have surged in popularity in recent years, especially among high school and college students. They have been a source of growth for beverage companies even as demand for more traditional drinks like soda has cooled. Coca-Cola considered a buyout of Monster earlier this year, but with a market capitalization of more than $10 billion, a deal for Monster would have been expensive, and Coke ultimately passed.
Health advocates are concerned about the use of energy drinks among adolescents, particularly when they are consumed alongside alcohol, said Amelia M. Arria, an epidemiologist who serves as director of the Center on Young Adult Health and Development at the University of Maryland School of Public Health.
“A person who co-ingests an energy drink and alcohol doesn’t understand how drunk they are,” Ms. Arria said. “Caffeine keeps you awake so you can keep drinking, and high levels of caffeine can mask intoxication.”
“In my opinion, some of the marketing messages go overboard about the health benefits of these drinks,” Ms. Arria added. “The term ‘energy drink’ is misleading. Energy should come from calories — this is more about stimulation.”
Studies have shown almost 30 percent of college students consume energy drinks regularly, Ms. Arria said. The high concentrations of caffeine they contain can produce cardiovascular complications, especially in young people or those who are sensitive to caffeine, she said.
A November 2011 report by the Drug Abuse Warning Network, produced under the auspices of the Department of Health and Human Services, showed a tenfold increase in emergency room visits linked to energy drinks from 2005 to 2008.
“Consumption of energy drinks is a rising public health problem because medical and behavioral consequences can result from excessive caffeine intake,” the report concluded. “A growing body of scientific evidence documents harmful effects, particularly for children, adolescents and young adults.”
About half the emergency room trips were made by patients 18 to 25 who had also used alcohol or other drugs, according to the Drug Abuse Warning Network report.
The amount of caffeine differs widely among drinks but can range from about 80 milligrams to more than 500 milligrams. By comparison, a 12-ounce cola contains about 50 milligrams of caffeine, while a 5-ounce coffee has about 100 milligrams.
In its statement, the American Beverage Association said “most mainstream energy drinks contain about half the caffeine of a similar-size cup of coffeehouse coffee. And the caffeine content our members voluntarily display on their packages reflects total caffeine amounts, including those that come from other sources, such as additives.”
Shares of Monster Beverage fell 55 cents, to $59.48, on Tuesday, while Pepsi fell 5 cents, to $73.12. Living Essentials is not publicly traded.
NELSON D. SCHWARTZ