Life, death and the beauty of unknowing

Caffeine is a bitter substance derived from the leaves, fruit and seeds of various plants and acts as a natural pesticide against threatening insects.

Caffeine is of course found in high amounts in the seeds of the coffee plant and the leaves of the tea bush but it's also commonly found in:

• Kola nuts - used to flavour cola drinks

• Cacao pods - used to make chocolate products, and guarana berries - which contain about twice the amount of caffeine as coffee beans.

The effects of caffeine on the body

Caffeine is a central nervous system stimulant which can increase your alertness and give you an energy boost. In the short term it can reduce physical tiredness, make you think faster and more clearly, increase your focus and improve your physical coordination.

However, this same stimulant effect can cause sleep problems, especially if you take caffeine too close to bedtime. If you are having problems sleeping, try cutting out caffeine (decaff alternatives are fine) after about 5 pm. If the problem persists, try cutting it out altogether for a couple of weeks to see if it helps.

At moderate levels (up to 400 mg a day - that's 4-5 cups of coffee or 8 cups of tea a day) it does not increase your risk of high blood pressure, abnormal heart rhythms, type 2 diabetes or cancer.

However, if you're pregnant, you should limit your caffeine intake from all sources to 200 mg a day. If you suffer from irritable bowel syndrome, irritable bladder, menopausal hot flushes or migraines, caffeine may make your symptoms worse.

Give yourself a trial of two weeks caffeine-free to see if your symptoms improve. Not everyone with these conditions is caffeine-sensitive, and there's no need to deprive yourself if it doesn't make a difference.

The main sources of dietary caffeine

Here is a rough indication of how much caffeine there is in common sources:

• Coffee - depending on type, generally between 60-150 mg

• Tea - standard black tea contains between 40-80 mg

• Cola drinks - 330 ml contains around 30-40 mg

• Energy drinks - a 250 ml can contains around 70-100 mg

• Chocolate - a 50 g bar of chocolate contains around 30-50 mg

Other sources of caffeine

Caffeine is also found in a number of different types of prescription and over-the-counter medicines, including some weight control products, cold and flu treatments and painkillers.

Some tips for reducing your caffeine intake

Although caffeine can be addictive to some degree, cutting back to within healthy limits doesn't need to be difficult, especially if you do it gradually over a week or two - here are some effective tips:

• Switch to decaffeinated coffee or tea

• Try alternative hot drinks such as fruit and herbal teas, green tea, chai and roasted grain drinks

• Replace energy drinks with caffeine-free soft drinks, fruit and vegetable juices, fruit smoothies and squashes (diet versions preferably).