Caffeine is the main ingredient in energy drinks. Caffeine can improve both mental and athletic performance. Moderate amounts of caffeine can help you feel more alert and improve memory and reasoning if you have not had enough sleep. Caffeine can also improve endurance if it's consumed before exercise. Energy drink makers claim that ingredients such as taurine, ginseng and other herbs provide extra energy and improve performance. There is no scientific evidence to confirm these claims.

How much caffeine do energy drinks contain?

Caffeine in energy drinks can vary. A 240ml can of energy drink can have 50mg-160 mg of caffeine. An average 227ml cup of brewed coffee has 100mg caffeine; a 227ml cup of tea has about 50mg and a 340ml soft drink (cola) has about 40mg caffeine.

Are energy drinks harmful?

Health experts say the consumption of 300mg of caffeine per day - the equivalent of three cups of coffee - is safe. Children under 12 should have less than 85mg caffeine. But some people are more sensitive to caffeine than others, so even one cup of coffee may be too much for them. And drinking too much caffeine can make you restless, nervous and prevent you from sleeping.

Moderate levels of caffeine are safe, but many energy drinks are not intended for children. Some labels say that no more than 500ml of energy drinks should be consumed each day.

Heath experts warn teenagers to drink water rather than energy drinks during exercise or training. Sports drinks contain controlled amounts of sugar and salt to help replenish nutrients lost through sweat and to help you exercise for longer. But energy drinks contain more sugar, which is difficult to absorb while exercising. Drinking too many energy drinks during exercise can lead to dehydration, heat stroke and even heart attacks. Energy drinks can be addictive, too. You may use them a few days in a row to get through exams. But stopping them can lead to withdrawal symptoms like headaches, mood swings or lack of concentration.

The bottom line ...

In June, the American Academy of Paediatrics recommended that energy drinks should never be taken by children or adolescents because the stimulants they contain can pose health risks.

Caffeine levels in popular drinks

Drink/food, Serving, Caffeine (mg)

Brewed coffee, 227ml, 65-120

Instant coffee, 227ml, 60-85

Espresso coffee, 28ml, 30-50

Brewed tea, 227ml, 20-90

Instant tea, 227ml, 24-31

Iced tea, 227ml, 9-50

Soft drinks (cola), 340ml, 30-60

Cocoa drink, 227ml, 3-32

Chocolate milk, 227ml, 2-7

Milk chocolate, 28ml, 1-15

Dark chocolate, 28ml, 5-35

How to get the buzz without caffeine ...

1. Move your body Revising for exams isn't a good reason for not exercising. One of the best ways to get more energy is to exercise. Twenty minutes of cardio exercise such as jogging, running or cycling is enough to get your heart pumping and those happy hormones circulating around your body.

2. Eat breakfast Breakfast is the most important meal of the day since it kick-starts your metabolism after a night without food. Skipping breakfast means your blood sugar and energy levels will be low.

3. Drink water If you are dehydrated, this will make you feel tired and sluggish all day. Make a habit of keeping a bottle of water handy everywhere you go; pop a refillable bottle in your bag, on your desk or by the television and take regular sips throughout the day.

4. Get enough sleep Teenagers need at least nine hours of sleep every night. If you get enough sleep, you won't need to turn to those energy drinks for a quick fix.