Taurine, energy drinks, and neuroendocrine effects

Taurine—an amino acid found in abundance in the human brain, retina, heart, and reproductive organs, as well as in meat and seafood—is also a major ingredient in “energy drinks” (Table 1).^1,2 Given the tremendous popularity of these drinks in the United States, it would seem important to know and to recognize taurine’s neuroendocrine effects. Unfortunately, little is known about the effects of taurine supplementation in humans.

This paper reviews the sparse data to provide clinicians some background on the structure, synthesis, distribution, metabolism, mechanisms, effects, safety, and proposed therapeutic targets of taurine.

TAURINE’S THERAPEUTIC POTENTIAL

Taurine has been reported to have widespread anti-inflammatory actions.^3,4 Taurine supplementation has been proposed to have beneficial effects in the treatment of epilepsy,⁵ heart failure,^6,7 cystic fibrosis,⁸ and diabetes⁹ and has been shown in animal studies to protect against neurotoxic insults from alcohol, ammonia, lead, and other substances.^10–16

In addition, taurine analogues such as homotaurine and N-acetyl-homotaurine (acamprosate) have been probed for possible therapeutic applications. Homotaurine has been shown to have antiamyloid activity that could in theory protect against the progression of Alzheimer disease,¹⁷ and acam­prosate is approved by the US Food and Drug Administration (FDA) for the treatment of alcohol use disorders.¹⁸

TAURINE CONSUMPTION

Energy drinks are widely consumed in the United States, with an estimated 354 million gallons sold in 2009, or approximately 5.25 L/year per person over age 10.¹ In 2012, US sales of energy drinks exceeded $12 billion,¹⁹ with young men, particularly those in the military deployed in war zones, being the biggest consumers.^20–22 Analyses have found that of 49 nonalcoholic energy drinks tested, the average concentration of taurine was 3,180 mg/L, or approximately 750 mg per 8-oz serving.^23,24 Popular brands include Red Bull, Monster, Rockstar (Table 1), NOS, Amp, and Full Throttle.

Taurine is plentiful in the human body, which contains up to 1 g of taurine per kg.²⁵ Foods such as poultry, beef, pork, seafood, and processed meats have a high taurine content (Table 2).^26–29 People who eat meat and seafood have plentiful taurine intake, whereas vegetarians and vegans consume much less and have significantly lower circulating levels³⁰ because plants do not contain taurine in appreciable amounts.^26,29

The typical American diet provides between 123 and 178 mg of taurine daily.²⁶ Consumption of one 8-oz energy drink can increase the average intake 6 to 16 times. A lacto-ovo vegetarian diet provides only about 17 mg of taurine daily, and an 8-oz energy drink can increase the average intake by 44 to 117 mg.²⁶ And since a vegan diet provides essentially no taurine,³⁰ energy drink intake in any amount would constitute a major relative increase in taurine consumption.

ATTEMPTS TO STUDY TAURINE'S EFFECTS

Since most clinical trials to date have looked at the effects of taurine in combination with other ingredients such as caffeine, creatine, and glucose^31–35 in drinks such as Red Bull, these studies cannot be used to determine the effects of taurine alone. In the few clinical trials that have tested isolated taurine consumption, data are not sufficient to make a conclusion on direct effects on energy metabolism.

Rutherford et al³⁶ tested the effect of oral taurine supplementation (1,660 mg) on endurance in trained male cyclists 1 hour before exercise, but observed no effect on fluid intake, heart rate, subjective exertion, or time-trial performance. A small increase (16%) in total fat oxidation was observed during the 90-minute exercise period. Since mitochondria are the main location of fatty acid degradation, this effect may be attributed to taurine supplementation, with subsequent improvement in mitochondrial function.

Zhang et al³⁷ found a 30-second increase in cycling energy capacity after 7 days of 6 g oral taurine supplementation, but the study was neither blinded nor placebo-controlled.

Kammerer et al³⁸ tested the effect of 1 g of taurine supplementation on physical and mental performance in young adult soldiers 45 minutes before physical fitness and cognitive testing. This double-blind, placebo-controlled randomized trial found no effect of taurine on cardiorespiratory fitness indices, concentration, or immediate memory, nor did it find any effect of an 80-mg dose of caffeine.

In sum, the available data are far from sufficient to determine the direct effect of taurine consumption on energy metabolism in healthy people.