ABSTRACT
This chapter provides an update on guanidinoacetic acid (GAA) pharmacology, efficacy and safety in medicine, sport and exercise and an overview of possible advanced formulas that contain GAA. GAA is a natural amino acid derivative and a metabolite in the urea cycle. It also appears as an intermediate in metabolic pathways of several amino acids, including glycine, serine and arginine. The idea that the addition of GAA to food will stimulate creatine synthesis and boost energy levels was first reported in 1951. The creatine-boosting effects of GAA was confirmed in a randomized, double-blind, placebo-controlled, parallel-group pharmacokinetics trial with 48 healthy young men and women who received single oral doses of GAA or a placebo. GAA supplementation has an acceptable side effect profile, with human studies usually finding no major adverse events after GAA intake, besides mild disturbances in clinical enzymes and creatinine and minor disturbances in the gastrointestinal tract.
