http://www.abc.net.au/health/thepulse/stories/2012/05/09/3471672.htm
Excerpt (more at link):
From the supermarket to the service station, if you’ve walked into a grocery store lately then chances are you’ve seen, and possibly even bought, an energy drink.
Around 20 per cent of beverages sold in Australian convenience stores are energy drinks. Given that the drinks claim to improve performance, alertness and concentration, it’s hardly surprising that their target market is young people, especially students and athletes.
Energy drinks get their kick from a range of ingredients including caffeine; herbal extracts, such as guarana and ginseng; and amino acids, such as taurine.
It’s the amount of caffeine in energy drinks that’s causing concern – the average energy drink contains 80mg of caffeine, and critics argue that some contain up to 300mg of caffeine (that’s equivalent to five cups of coffee). Experts are worried an increasing number of this group are experiencing nasty side effects after they drink large quantities of energy drinks, or when they drink them mixed with alcohol.
Adverse effects
When you ingest caffeine, it stimulates the body’s fight or flight response, producing a surge of adrenaline.
If our bodies are subjected to too much adrenaline, we can experience seizures, chest pain, heart palpitations and agitation – these are all signs of caffeine toxicity.
When Dr Naren Gunja, medical director of NSW Poisons and clinical toxicologist at Westmead Hospital, saw a case of caffeine toxicity in an emergency ward he decided to formally investigate the effects of caffeinated energy drinks.
He found that between 2004 and 2010 there were around 300 calls made to the NSW Poisons Information Centre regarding toxicity – or poisoning – related to the consumption of energy drinks. Reports rose from 12 calls in 2004 to 65 calls in 2010. The vast majority of these related to ‘recreational’ use of energy drinks, with affected ‘recreational users’ aged 15 to 21 years.
The number of energy drinks consumed in one session varied, but ranged from one to 80 – the mid-point (median) was five.
Importantly, almost half of these so-called recreational users had also ingested alcohol, caffeine tablets, ecstasy and amphetamines or other caffeinated beverages at the same time.
“This suggests that knowledge of energy drink effects and toxicity is poor, and mixing of substances is not seen as a problem in this cohort of adolescents and young adults,” Gunja and colleagues wrote in the Medical Journal of Australia.
“We know mixing alcohol and caffeine is a big problem because it alters your perception and ability to sense how drunk you are. So they may say ‘I’m not that drunk, I’m wide awake’ because of caffeine, but they are actually quite intoxicated because of the alcohol.”
Gastrointestinal (stomach and gut) upsets and heart palpitations were among the most common symptoms in these reports. But there were also signs of serious caffeine toxicity including hallucinations, seizures and cardiac ischemia (where the heart muscle doesn’t receive enough blood).
“What was alarming was the types of things that were happening to people such as cardiac, neurological and behavioural effects,” Gunja says.