Caffeine is a drug. Most people who drink caffeine on a regular basis develop a tolerance to its effects. This means that, over time, you need to drink more and more cups of coffee, tea, cola or energy drinks to get a caffeine “buzz”. However, caffeine is generally safe to use at levels of up to 250 mg per day (about two cups of drip coffee or three shots of espresso). Regular large amounts (over 350 mg/day) may cause dependency (“caffeinism”) and adversely affect health.

The fact that many people experience caffeine-withdrawal symptoms when any heavy coffee drinking is suddenly reduced also indicates that caffeine is an addictive substance. As little as 1-2 cups of coffee (100-200 mg caffeine) daily can produce withdrawal effects which are immediately relieved by getting some caffeine. However, unlike many addictive substances, caffeine can be given up fairly easily by most people.

When it comes to caffeinated drinks, moderation is the key. A moderate intake of caffeine – up to 200 mg per day – is unlikely to do any harm to most people, and may even bring some benefits. However, excessive caffeine intake is bad for your health.

There are about 200 mg of caffeine in:

• 2-3 8 fl oz cups of drip coffee
• 2-3 shots of espresso
• 2 cappuccinos
• 2 - 3 8 fl oz cups strong black tea (or 5 cups medium strength black tea)
• 8 12 fl oz glasses/cans of iced tea
• 5 cans Diet Coke
• 2 Red Bull drinks
• 2 No-Doz regular strength tablets
• 3 Excedrin tablets
• 1 Dexatrim tablet

If you experience any of the following, you may be getting too much caffeine:

• chronic insomnia
• high blood pressure
• persistent anxiety and depression
• restlessness
• heart palpitations
• headaches
• nervousness
• stomach upset
• increased need to urinate

If you are sensitive to caffeine, you may “get the jitters” and experience increased body tension, headaches, and other stress-like symptoms from as little as one cup of coffee.

Overdose

Overdose from caffeine is possible, but it's rare. You risk overdose if you eat or drink more than 10 g of caffeine in one session – that's over 160 cups of regular instant coffee, which is unlikely, even for the most hard-core coffee addict!

When not to have caffeine

If you are pregnant you should avoid caffeine as it may increase the risk of miscarriage and low birth-weight. If you are nursing, diabetic or have a heart condition or stomach ulcers, you should probably abstain from caffeine altogether.

Children and caffeine

As little as 100 mg of caffeine ( two cans of cola drinks) can cause anxiety in a child and reduce his or her ability to sleep. Children who regularly choose cola or energy drinks over water, milk or fruit juice may also be missing out on essential nutrients such as calcium and vitamins, and are at risk of dehydration.

Some experts also blame caffeine for a number of behavioral problems, such as a fidgeting, distraction and inattentiveness. Children under eight should not have any caffeine.