Caffeine is present in coffee, tea, chocolate and cola drinks and is an addictive central nervous system stimulant widely consumed for its positive effect on mood, well-being and performance.13 Its pharmacological effect is due to its ability to compete for absorption with adenosine, an inhibitory neurotransmitter, and override this natural sedative. The negative effects on mood of excess caffeine include restlessness, nervousness, anxiety, irritability and poor concentration.14 Excess caffeine can also encourage glucose intolerance through its stimulatory effect on the adrenals.15 Withdrawal symptoms are a consequence of the detoxification process and can be unpleasant but are usually complete following five days¡¯ total abstinence. It was suggested that a gradual withdrawal may be preferable for some people.

Approximate levels of caffeine  

a cup of filter coffee ? 100mg
a cup of instant coffee ? 66mg
a cup of tea made with loose leaf tea ? 41mg
a cup of tea made with a teabag ? 40mg
a can of cola ? 23mg
a 50g bar of plain chocolate ? 20mg
a 50g bar of milk chocolate ? 7mg
a cup of ¡®hot chocolate¡¯ drink ? 5mg
a cup of ¡®green¡¯ tea ? 4mg
a cup of ¡®decaff¡¯ ? 3mg
a fizzy drink containing the herb guarana 1 -
a cup of ¡®Red Bush¡¯ herbal tea 2 -

1 a South American herb closely related to caffeine but possibly not as toxic
2 this is naturally caffeine free although it does contain tannin, an ¡®antinutrient¡¯ which binds to minerals such as iron and zinc in the gut thus preventing their absorption.