Caffeine is quite possibly the world’s favourite ‘drug’. Many of us can’t begin the day without a strong cup of caffeine-fuelled coffee to perk us up. But caffeine does more than give us a jump-start in the morning - there’s growing evidence that it has other health benefits too.

What is caffeine?

Caffeine is found naturally in some plants but can also be man-made. It acts as a stimulant to the central nervous system and is also a diuretic (which means it helps rid your body of fluids). Rich natural sources include: coffee, tea, chocolate and colas.

You can also take caffeine in supplement form - great for keeping you mentally alert and for relieving temporary tiredness. Caffeine is also added to some medicines such as pain relievers and cold remedies and is a common ingredient in energy drinks.

Why do I need caffeine supplements?

Caffeine is best known as a stimulant useful for perking us up and relieving short-term drowsiness. Because it’s not collected in the bloodstream or stored in the body it reaches the brain quickly where it excites the nervous system before eventually getting passed out in our urine. It works by blocking the action of a natural brain chemical called ‘adenosine’ which binds to special receptors in the brain to slow down nerve cell activity and cause sleepiness. But when you consume caffeine this binds to those special receptors instead keeping you peppy and alert.

You’ll often find caffeine in headache medicine this is because it constricts blood vessels which can decrease pain. Studies have shown that caffeine mixed with ibuprofen cures a tension headache quicker than pain-medicine alone.

Some studies also suggest caffeine may have an antidepressant effect. This may be because caffeine acts on chemicals in the brain including the ‘happy’ hormone serotonin (too little serotonin is linked to depression). In one study from Harvard, suicide risk was found to decrease with increased caffeinated coffee consumption. Other evidence points to the fact that caffeine may enhance memory and mental function.

The benefits of caffeine are many - it’s associated with increased stamina and physical endurance, decreased muscle pain and increased weight loss. It’s also though to have antioxidant content (the health boosting compounds that help protect against cell damage) and some studies link caffeine consumption to reduced risk of cardiovascular disease and cancer. More research is needed in these areas.

Can too much caffeine be bad for you?

Yes. If you consume more than 500 to 600mg a day you may experience a range of unpleasant side-effects including: tachycardia (rapid heartbeat), restlessness, insomnia, muscle tremours and anxiety. Because it’s a diuretic it will also make you wee more often than normal.

If you stop caffeine abruptly it can cause withdrawal symptoms including headaches, irritability and nausea. Sensitivity to caffeine varies between individuals. Some people get jittery even if they consume just a little caffeine.

Caffeine in large quantities may interfere with the absorption of calcium which may lead to the brittle bone disease osteoporosis.

It is also thought to exacerbate symptoms of fibrocystic disease (lumpy breasts) and high consumption during pregnancy is associated with low-birth weight. The Food Standards Agency advises pregnant women to limit their caffeine consumption to 200mg per day (roughly two coffee mugs worth). Freshly ground coffee tends to contain higher levels of caffeine per mug than instant coffee.

Caffeine is also an appetite suppressant and may have a negative impact on nutrition if given to children.

The EU Scientific Committee on Food notes that a dose of 5mg caffeine per kilogram bodyweight (so 300mg for a 60kg person) may lead to arousal, irritability, anxiety and nervousness in some people. There have been some reports of people overdosing on energy drinks and requiring assistance from A&E. If you are taking caffeine supplements or energy drinks keep tabs on how much you are consuming so that you don’t over do it.For most adults two to four cups of brewed coffee daily is unlikely to cause any harm (this amounts to between 200-300mg).