Creatine Kinetics, Synthesis From Glycine and Response to Creatine and Amino Acid Supplement in Healthy Humans

The goal of the present study is to quantify the rate of synthesis of creatine in healthy controls and endurance trained subjects. In addition, the effect of oral creatine supplement for seven days on creatine kinetics will be examined. Ten healthy controls (age 20-35 years) and ten endurance trained subjects will be recruited by advertisement. Endurance trained subjects will be recruited from health clubs. They will be screened for absence of any chronic disease (history, physical examination, CBC, metabolic and liver panel, urinalysis). A DEXA measurement will be done to quantify whole body skeletal muscle mass. For five (5) days prior to the study, they will be placed on a creatine-free (essentially meat-free) diet. Dietary compliance will be ensured by repeated communication with the subject, by nurse coordinator and the CRU Nutritionist. Subject will maintain daily record of the food intake for validation. On the last day, i.e. 24 hours prior to the tracer study, subject will collect the 24 hours urine sample and bring it to the CRU on the day of the study.