Abstract: A nutritional supplement contains 50% to 80% by weight of trimethylglycine; 5% to 30% by weight of L-?-glycerophosphorylcholine; 5% to 15% by weight of caffeine; and 5% to 10% by weight of an ingredient selected from the group consisting of an L-amino acid, creatyl-L-leucine, Corynanthe yohimbe bark extract, theacrine, and mixtures thereof. The nutritional supplement is useful for enhancing energy, mental acuity, cognitive performance, and reaction time in a subject in need thereof.