Table 4.

Potential stimulants contained in energy drinks that may affect performance capacity

Ingredient	Potential ergogenic value	Scientific support
Caffeine	Stimulant. Increases metabolism and lipolysis [2,8,9,61].	Increases alertness, mood, cognitive function [2,8,9,61]. Increases fat oxidation, spares glycogen utilization, improves exercise [7,9-11,62-65].
Guarana	Natural source of caffeine. Similar properties to caffeine.	Similar to caffeine effects.
Green Tea Extract	Contains high amounts of caffeine and catechin polyphenols (e.g., epigallocatechin gallate or EGCG). Serves as antioxidant. Similar effects as caffeine [66,67]	Some supportive evidence of increased metabolism [68-76]. Specific role at dosages found in ED is unknown.
Synephrine	Alternative to ephedrine. Naturally derived from Citrus aurantium. Stimulant with less cardiovascular effects than ephedrine. Purported to increase metabolism and promote weight loss.	Evidence of a mild stimulant effect on metabolism and weight loss [77-82]. No known effects at dosages found in ED.
Yerba mate	Contains three xanthines (caffeine, theobromine, and theophylline). Similar properties to caffeine	Similar to caffeine effects. Some supportive evidence [83-85] No known effects at dosages found in ED and ES.
Yohimbine	Alkaloid with stimulant and aphrodisiac properties [86-90].	Similar to caffeine effects. Effects at dosages found in ED are unknown.
Tyramine	Naturally-occurring monoamine derived from tyrosine. Acts as a catecholamine (dopamine, NE, Epi) releasing agent. Degraded to octopine. Increases blood pressure and can serve as neurotransmitter [91-93].	Mild cardiovascular stimulant. Effects at dosages found in ED / ES are unknown.
Vinpocetine	Alkaloid of vincamine extracted from periwinkle plant (Vinca) minor. Vasodilatory and memory enhancing properties [94,95].	No known effects at dosages found in ED or ES.