Guanidinoacetic Acid With Creatine Compared With Creatine Alone for Tissue Bioenergetics, Hyperhomocysteinemia and Exercise Performance: a Randomized Double-blind Superiority Trial

Targeting energy-demanding tissues in health and disease continues to be a challenging task in human nutrition and biomedicine. Impaired bioenergetics accompanies many different conditions, including cardiometabolic diseases, neurodegenerative disorders or high-intensity exercise, with various dietary interventions developed to restore cellular energy. Creatine is recognized as a beneficial and safe energy-boosting agent in both athletic and clinical environments. However, its effectiveness in specific conditions seems to be fairly restrained due to its limits in transportability and performance. Guanidinoacetic acid (GAA), a metabolic precursor of creatine, appears as a novel energy-enhancing supplement, with GAA being superior to creatine in facilitating creatine concentrations in the human brain and skeletal muscle. This perhaps happens due to GAA interaction with cellular transporters previously dismissed as untargetable carriers by other similar therapeutics. On the other hand, GAA loading remains under scrutiny due to its hyperhomocysteinemia-inducing potential, and possible neurotoxic effects. Co-administration of creatine and GAA has been recently proposed as a better strategy comparing to administration of each compound per se. Besides providing a competitive advantage for enhanced levels of tissue creatine, GAA-creatine mixture might also diminish side effects related to isolated GAA administration. However, no human studies so far evaluated the effects of this mixture. In the present study, the investigators compared the impact of 4-week co-administration of GAA and creatine vs. creatine administration alone on serum biomarkers, exercise performance and tissue bioenergetics in healthy young men.