Worldwide production of coffee exceeds 7 million metric tons annually and in the UK we drink on average three cups a day - equivalent to 225mg/day of caffeine (1), but is there more to our favourite beverage than instant success?
A Quick History
Legend has it that coffee was discovered in Ethiopia in the third century AD, by a goatherd who noticed his goats dancing with unusual energy after eating coffee berries. A local monastery acquired the knack of making a quick brew and found themselves able to stay awake for hours on end – very useful for early morning prayers. Roasting the beans didn’t catch on until the 13th century and its popularity gradually reached the Middle East and North Africa, hitting Europe in the early 17th century and Britain by 1650. The first coffee house in the UK was opened in Oxford that year (2). Unfortunately, the conviviality it fostered was initially seen as a threat to religious life by the Catholic Church until the Pope, Clement VIII, tried a cup for himself and thereafter gave it his blessing.
Basic Botany and Brewing Tips
The coffee plant is a tropical evergreen shrub propagated from seed. The three main cultivated species are Coffea arabica, C. liberica and C. robusta/canephora and all produce green berries, each containing two seeds. These are dried and roasted to reduce moisture content and improve flavour. In this brittle form they are suitable for grinding. The caffeine content of Robusta coffee (at 8%) is twice that of Arabica. The ideal infusion time is two minutes, which extracts about 80% of the caffeine, but excludes some of the less soluble bitter components. Unblended coffee usually contains Arabica beans, whereas the other varieties find their way into blended products, which occupy the majority of the market. Decaffeinated coffee still contains up to 3% residual caffeine, despite repeated extractions with dichloromethane as a solvent.
The Chemistry of Caffeine
The list of natural chemicals inside a single roasted coffee bean would give anybody palpitations, with over 300 documented constituents of which caffeine is the best known. It has a measurable stimulant and diuretic property even when consumed in modest quantities - equivalent to 2 cups of strong coffee. Caffeine belongs to a group of compounds known as methylxanthines, which have been widely researched for their pharmacological effects (3), stimulating the heart rate and the central nervous system, increasing urine output (diuresis) and relaxing the smooth muscles of the chest. Examples of related drugs include theophylline and aminophylline but the medical use of caffeine still requires further research.
Positive Findings
- Caffeine is our favourite psychoactive substance and despite a few health fears, retains its popularity worldwide. Elevating driver fatigue with a couple of cups of strong coffee is accepted advice from the UK Department for Transport. It takes about 15 mins for the caffeine to reach the nervous system, but blood plasma levels peak at around 60 mins. The liver excretes the drug at a fixed rate related to its half life of approx. 3 hours - the length of time taken to reduce plasma levels by 50%.
- Research on measuring the effect of caffeine on cognitive function in terms of alertness, short term memory and reaction time also yields positive results, particularly on older people where there is some evidence supporting a protective role for caffeine in preventing the development of Parkinson's disease (4).
- The use of caffeine-based supplements in sport to enhance performance received a boost when the ban on these products was removed by the IOC in 2004. Athletes participating in endurance events such as cycling and running may benefit significantly from caffeine intakes of 2.5 - 6mg/kg body weight - which equates to at least 2 mugs of strong coffee for a 70kg male, but locate the toilets first (4).
- One warning note - pregnant women are advised by the Food Standards Agency to limit their intake to 300mg/day (or 3 mugs of strong coffee) because caffeine molecules cross the placenta and affect the unborn child in the same way as the adult - leading to an increased risk of miscarriage (4).
- The unregulated nature of caffeine as a drug belies its potency, and while there appear to be few serious risks, the advice is similar to that issued for alcohol - drink in moderation and build in a weekly detox day without caffeine so that your liver can remove all traces - until you see a nice alternative source - such a pot of tea, a glass of coke or a bar of chocolate!
References:
- FAO Production Yearbook 1990. Leading Coffee Producing Countries of the World. FAO/UN Vol 44.
- Davidson A. 2002. The Penguin Companion to Food. Penguin Books.
- Rang H, Dale M, Ritter J. 2000. Pharmacology. Churchill Livingstone.
- Merryfield C. 2008. Fact or Fiction: Caffeine. Complete Nutrition Vol 8, No 3.
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