Despite recommendations against the use of creatine by anyone under age 18, more than two-thirds of sales clerks at health food stores told a researcher posing as a 15-year-old male football player to give it a try.

Creatine is a naturally occurring compound involved in the production of energy in the body used by athletes, bodybuilders, wrestlers, sprinters, and others who to gain muscle mass.

Both the American Academy of Pediatrics and the American College of Sports Medicine recommend against its use by anyone under the age 18.