Energy drinks like Red Bull and Monster Energy have levels of caffeine that may be harmful to children who consume them often, a study showed.

Some of the ingredients in the drinks are understudied and not regulated, according to a review of previous research and surveys in the March issue of the journal Pediatrics. Children with diabetes, mood disorders and heart, kidney or liver diseases may have reactions including heart palpitations, seizures, cardiac arrest or even death, the authors said.

Nearly one-third of kids 12 to 14 years old regularly consume these beverages, which contain caffeine, sugar and other additives, said study author Judith Schaechter, associate professor of pediatrics at the University of Miami. Of the 5,448 U.S. caffeine overdoses reported in 2007, 46 percent occurred in those younger than 19, Schaechter and her co-authors said.

“Pediatricians need to be aware of the possible effects of energy drinks,” said Steven Lipshultz, a professor and chairman of the Department of Pediatrics at the University of Miami School of Medicines and a study author. “Toxicity surveillance should be improved and regulations of energy-drink sales and consumption should be based on appropriate research assessing energy drink safety.”

Sales of energy drinks were $6.9 billion in 2009 compared with $6.5 billion in 2008, according to John Sicher, publisher and editor of Beverage Digest. Sales for 2010 aren’t yet available and are expected to be even higher, he said.

“Red Bull Energy Drink is available in over 160 countries because health authorities across the world have concluded that Red Bull Energy Drink is safe to consume,” said Patrice Radden, a spokeswoman in Santa Monica, Calif,, for closely held Red Bull based in Fuschl am See, Austria. “Last year alone, over 4 billion cans and bottles were consumed across the world.”

Energy drinks and their ingredients are regulated by the Food and Drug Administration, she said in an e-mail.

A telephone call to Hansen Natural Corp. in Corona, Calif., which makes Monster Energy, was answered by a person who declined to be identified and said she couldn’t comment on the study.