February 10/Chicago/The Associated Press -- Nearly three out of four U.S. children and young adults consume at least some caffeine, mostly from soda, tea and coffee. The rate did not budge much over a decade, although soda use declined and energy drinks became an increasingly common source, a government analysis finds.

Though even most preschoolers consume some caffeine-containing products, their average was the amount found in half a can of soda, and overall caffeine intake declined in children up to age 11 during the decade.

The analysis is the first to examine recent national trends in caffeine intake among children and young adults and comes amid a U.S. Food and Drug Administration investigation into the safety of caffeine-containing foods and drinks, especially for children and teens. In an online announcement about the investigation, the FDA notes that caffeine is found in a variety of foods, gum and even some jelly beans and marshmallows.

The probe is partly in response to reports about hospitalizations and even several deaths after consuming highly caffeinated drinks or energy shots. The drinks have not been proven to be a cause in those cases.

The new analysis, by researchers at the Centers for Disease Control and Prevention, shows that at least through 2010, energy drinks were an uncommon source of caffeine for most U.S. youth.

The results were published online in the journal Pediatrics.

The American Academy of Pediatrics recommends against caffeine consumption for children and teens because of potentially harmful effects from the mild stimulant, including increases in heart rate and blood pressure, and worsening anxiety in those with anxiety disorders.

Dr. Stephen Daniels, chairman of the academy's nutrition committee, said caffeine has no nutritional value and there's no good data on what might be a safe amount for kids.

Evidence that even very young children may regularly consume caffeine products raises concerns about possible long-term health effects, so parents should try to limit their kids' intake, said Daniels, head of pediatrics at the University of Colorado's medical school.

The authors analyzed national health surveys from 1999 through 2010, involving a total of 22,000 from age 2-22. The children or their parents answered questions about what they ate or drank the previous day, a common method researchers use to assess Americans' diets.

In 2010, 10% of daily caffeine came from energy drinks for 19- to 22-year-olds; 2% for 17- to 18-year-olds, and 3% for 12- to 16-year-olds. For younger kids, the amount from energy drinks was mostly minimal or none during the study.

The average intake in the study was about 60-70mg daily, the amount in a 6oz. cup of coffee or two sodas, said lead author Amy Branum, a health statistician at the CDC's National Center for Health Statistics. For the youngest kids, it was much less than that.

Use of energy drinks increased rapidly during the study, even if they did not amount to a big portion of kids' caffeine intake, and that rise "is a trend researchers are going to keep their eyes on," Branum said.

Soda was the most common source of caffeine throughout the study for older children and teens; for those up to age 5, it was the second most common after tea. Soda intake declined for all ages as many schools stopped selling sugary soft drinks because of obesity concerns.

The American Beverage Association, whose members include makers of soft drinks and energy drinks, maintains that caffeine has been safely added to drinks as a flavor enhancer for more than 100 years.

"In amounts often found in coffee and some energy drinks, caffeine can have a pleasant stimulating or alerting effect," the group's website says.

Maureen Beach, a group spokeswoman, said the study confirms that kids' consumption of caffeine from soft drinks has decreased.