One 500ml energy drink can contain up to 17 level teaspoons of sugar and the same amount of caffeine as in 2 cups of espresso.

Caffeine is a stimulant of the central nervous system, which has effects on the brain that make you feel more alert. Large amounts of caffeine may cause serious heart and blood vessel problems such as heart rhythm disturbances and increases in heart rate and increases blood pressure. Caffeine may also harm children's still-developing cardiovascular and nervous systems. The caffeine content in most energy drinks ranges from about 80 mg (roughly the same as a mug of coffee) to about 150 mg per serving. Energy drinks which contain over 150 mg of caffeine per litre must be clearly labelled as having 'high caffeine content'.

They play a key role in energy metabolism. They are water-soluble which means that they are not absorbed by your body but they are passed out of your system with no toxic buildup. This allows energy drinks to contain amounts well beyond the recommended daily allowance without being harmful.

Like taurine, many people think ginseng boosts mental or physical performance, but there is little scientific research to support that theory. Much like caffeine, in large quantities ginseng can cause overstimulation, restlessness, rapid heartbeat, anxiety, headache, and insomnia. The problem is that we don’t know exactly how much ginseng is in an energy drink. Additionally, ginseng should not be consumed by people with high blood pressure, hyperactivity, insomnia, colds or flus and by women who are pregnant or breastfeeding. Yet, energy drink labels make no mention of the quantity of ginseng or its potential side effects.

Made from the leaves of the ancient Chinese ginkgo tree, this herb is said to fight mental fatigue and improve memory. Yet the research regarding these claims is conflicting.

This extract, from the seeds of the South American guarana plant, delivers twice the caffeine of coffee per serving. Its claims that it stimulates weight loss and fights fatigue.

A scheme about their content