This article was originally published in The MuscleTalker August 2013 edition
Glucuronolactone (also known as D-Glucuronolactone, DGL, D-Glucurono-3,6-Lactone or D-Glucoronic Acid) is a key ingredient included in many popular stimulant energy and pre-workout drinks. It is a naturally occurring chemical produced from the metabolism of glucose in the liver and has been shown to increase endurance and improve reaction times at supplemental doses, making it an effective ergogenic stimulant and nootropic.
Stimulants like caffeine have vasoconstricting properties. Vasoconstriction is where the blood vessels narrow, increasing blood pressure and hotness which is one of the negative side effects from stimulant-containing drinks. One key ingredient in pre-workout formulas is nitric oxide - also known as arginine alpha-ketoglutarate (AAKG) - a vasodilator which helps give rise to those much sought after muscle pumps from a workout. Vasoconstrictor stimulants like caffeine cancel out some of the effects of AAKG, which is where glucuronolactone comes in: unlike other stimulants, it doesn't have any vasoconstricting properties. Thus it is often a preferred ingredient in stimulant drinks, like Red Bull as well as pre-workout drinks.
The exact effectiveness of glucuronolactone is unknown as previous research involves the study of energy drinks which also contain caffeine and taurine. It is therefore impossible to ascertain which compound was responsible for the enhanced benefits. However, there are a number of studies which demonstrate improved attention, reaction, speed and performance with the combination of glucuronolactone, caffeine and taurine.
Glucuronolactone is found in relatively small amounts, naturally. Red wine is perhaps the strongest natural source, with approximately 20mg of glucuronolactone per litre. Doses of as little as 0.5g have been shown to have an ergogenic effect, and doses of up to 1g are commonly found in supplements.
Glucuronolactone was said to be a carcinogen in larger amounts, but this has been dismissed as a rumour and debunked in the British Medical Journal and it is not restricted by the US FDA.