Creatine Supplementation and the Brain: Have We Put the Cart Before the Horse?

Creatine is an important regulator of brain bioenergetics, yet the efficacy of creatine supplementation (CrS) in the brain remains largely unknown. Measurement of brain creatine using proton (1H) and phosphorus (³1P) magnetic resonance spectroscopy is highly sensitive to voxel placement, signal quality, analysis pipelines, and reporting conventions which can obscure the detection of biological responses to CrS. There is evidence that CrS increases brain creatine, but this response may be dose and/or duration dependent. CrS provides some benefits during acute periods of metabolic stress such as sleep deprivation, mental fatigue, and hypoxia. Emerging clinical data also suggest potential therapeutic effects from CrS for Alzheimer's disease, major depressive disorder, and mild traumatic brain injury (mTBI), although findings across conditions remain preliminary and inconsistent. Further, CrS shows some promise for improving aspects of sleep quality. The purpose of this narrative review is to: (1) outline methodological considerations in the quantification of brain creatine, (2) discuss the divergent effects of CrS on brain creatine levels and measures of brain function, (3) examine the purported mechanistic actions of CrS for improving brain health and function, (4) highlight critical gaps and limitations which should be considered moving forward, and (5) identify future research directions involving CrS and the brain.