Caffeination : the pros and cons of our favourite stimulant

The discovery of every popular stimulant cultivates mythology, and there is the quaint legend of a Yemeni shepherd named Kaldi who was said to have first noted the stimulant properties of coffee as he tended his sheep. It is claimed that he noticed that the sheep became hyperactive after eating the red "cherries" from a certain plant when they changed pastures. Inquisitive he tried a few himself, and soon became as hyperactive as his herd. A passing monk heard his story and boiled the berries, from which he distilled a bitter beverage capable of dispersing sleep and weariness. Another legend is said to have given us the name "mocha". An Arabian named Omar had been banished to the desert with his followers to die of starvation. In his desperation he boiled and ate the fruit from an unknown plant which it is said saved them. Their survival was taken as a religious sign by the residents of the nearby town of Mocha, after which the plant and its beverage are named.

From its very introduction coffee’s invigorating powers have understandably linked it with religion, and each tradition claims its own unique affiliation with the plant. Islamic legend ascribes the discovery of coffee to the devout Sheikh Omar, who is said to have found coffee growing wild whilst living as a recluse in Mocha, a famous coffee producing region of the Yemen. He is said to have boiled some of the berries and discovered the stimulating effect of the resulting brew upon administering it to locals stricken with a mysterious ailment, thereby curing them. The Sheikh went on to cure the King of Mocha’s daughter with coffee. The wonderous medicine soon found its way to Mecca where the first coffee houses are claimed to have arisen. Although these ‘Kaveh Kanes’ were originally religious meeting places, they soon became popular places of social gathering. The Arabic word for coffee ‘kahwah’ is also a word for wine, as the pulp of the coffee bean was often fermented to make a potent liquor. Although the Koran outlaws intoxicating beverages, it was successfully argued that coffee was more a stimulant than an intoxicant and the liquor remained. However coffee was discovered, the fact remains that the coffee plant originated from the Ethiopian region of Kaffa. The Ethiopian Galla tribe are known to have widely used coffee as a foodstuff, but not as a drink. It is believed that the monks of Ethiopia may have chewed on the berries as a stimulant for centuries before it was first brewed as a hot drink. Galla huntsmen would wrap coffee beans in animal fat as their only source of nutrition whilst on raiding parties. The use of coffee as a stimulant may thus have originated in Africa around 575 A.D. where the beans were so important they were even used as money. From Eastern Africa the use of coffee spread to the Yemen, Arabia and Egypt where it entered popular daily life and culture. Exactly where and when coffee was first cultivated is still disputed, but most authorities believe that it was first grown in Arabia near the Red Sea around 675 AD.

The Turks were perhaps the first country to drink coffee as an infusion, often adding spices such as clove, cinnamon, cardamom and anise to the brew. However Arabian texts dating from around 900 AD refer to an Ethiopian drink known as ‘buna’, similar to the Ethiopian word for brewed coffee. It was however to be many centuries before coffee was introduced to countries outside the Arab world, whose inhabitants believed it to be a precious commodity and guarded its secret jealously. So central did coffee become in the Turkish way of life, that Turkish law made it legal for a woman to divorce her husband if he fail to provide her with her daily quota of coffee. In fact the export of the plant from the Moslem world was strictly forbidden, and the actual spread of coffee, initially to the East, was started illegally. Arab traders are credited with first introducing coffee to Sri Lanka as early as 1505, and an Arab by the name of Baba Budan allegedly smuggled beans to some mountains near Mysore in South-Western India on his return from a pilgrimage to Mecca in the 17th century. There he started a small plantation where the descendants of those original plants are still to be found still growing fruitfully today.

By 1453 coffee had reached Constantinople with the expansion of the Ottoman Empire, and the world's first coffee shop, Kiva Han, opened there in 1475. The first coffee houses of Constantinople were opened in 1554, and their advent provoked religiously inspired riots. Perhaps it was only the profitability of taxing the nascent coffee trade that allowed it to establish its roots securely in other nations. By the late 16th Century the first tradesmen had introduced the eastern elixir into European culture, and this became a lucrative business for Venetian traders by 1615. Throughout the 17th and 18th centuries coffee houses proliferated throughout Europe, establishing a social habit that has persisted for over 400 years. Although most of the coffee exported to European markets came from the ports of Alexandria and Smyrna, the scale of the demand for coffee and the size of the export taxes imposed at these ports led European traders to try cultivating coffee in other countries. With the explosion in the popularity of coffee houses the European powers were soon competing against each other throughout the 17th Century to establish coffee plantations in their respective colonies. In 1658 the Dutch began the large scale cultivation of Mocha in Sri Lanka, and by 1699 they had successfully transplanted cuttings to Java, and by 1718 to Surinam.

The history of the introduction of the coffee plant to the Americas began in 1714 when the French succeeded in bringing a live cutting of a coffee tree to the island of Martinique in the West Indies. From its successful introduction there coffee was taken to South America, and was first grown in North Brazil around 1727. However the coffee plant failed to thrive in the poor climate of Northern Brazil, and this caused cultivation to move first to Rio de Janeiro, and then to San Paolo and Minas, where the coffee plant found its ideal habitat. Coffee growing began to develop in earnest until it became the most important economic resource of Brazil, accounting for 97% of world coffee production at the beginning of the 20th Century, all from that first cutting in Martinique. It wasn’t until 1878 that the coffee tree finally returned to its ancestral home, when the British ironically established the first plantations of Kenya’s future coffee industry on the door step of Ethiopia.

Coffee begins its story in the United States almost four hundred years ago, when Captain John Smith helped to found the ill-fated colony of Virginia at Jamestown. However by 1668 coffee had replaced beer as New York's City's favourite breakfast drink, and “The Boston Tea Party” of 1773 made drinking coffee a patriotic statement. The consumption of coffee continued to grow aided by such American industrial innovations as the packing roast coffee in vacuum tins and the invention of instant soluble coffee at the beginning of the 20th Century, and also by the invention of freeze dried coffee by Nestle in 1938 as a solution to surplus world coffee production. The advent of Prohibition in 1920 saw coffee sales boom, and by 1940 the US had become the world’s primary importer of coffee, accounting for 70% of the global harvest. The entry of the United States into the Second World War even led to widespread panic hoarding of coffee which forced its rationing.

A religious brew

No recreational drink, with the obvious exception of alcohol, has caused quite as much religious exception and fervour as the introduction of coffee. In 1454 the Mufti of Aden visited Ethiopia and was reportedly impressed with the drink, which cured him of some affliction. His approval soon made it a popular beverage amongst the tribes of the Yemen who adopted it in religious ceremonies and introduced it to Mecca. It was introduced widely throughout Islam and became almost synonymous with the Muslim world, ironically in much the same way as coffee is identified with the American way of life today, so much so that in 1615 upon its introduction to Venice certain clerics suggested that it should be excommunicated as the “Devil’s work”. However coffee was popularised by Pope Clement VIII who is said to have enjoyed it so much that rather than banishing it he baptized it, reportedly exclaiming that "coffee is so delicious it would be a pity to let the infidels (Moslems) have exclusive use of it."

From its very introduction coffee’s invigorating powers have understandably linked it with religion, and each tradition claims its own unique affiliation with the plant. Islamic legend ascribes the discovery of coffee to the devout Sheikh Omar, who is said to have found coffee growing wild whilst living as a recluse in Mocha, a famous coffee producing region of the Yemen. He is said to have boiled some of the berries and discovered the stimulating effect of the resulting brew upon administering it to locals stricken with a mysterious ailment, thereby curing them. The Sheikh went on to cure the King of Mocha’s daughter with coffee. The wonderous medicine soon found its way to Mecca where the first coffee houses are claimed to have arisen. Although these ‘Kaveh Kanes’ were originally religious meeting places, they soon became popular places of social gathering. The Arabic word for coffee ‘kahwah’ is also a word for wine, as the pulp of the coffee bean was often fermented to make a potent liquor. Although the Koran outlaws intoxicating beverages, it was successfully argued that coffee was more a stimulant than an intoxicant and the liquor remained.

Not all Islamic clerics were content with the widespread introduction of coffee to their religious culture however, and religious divisions over coffee in the Islamic world finally came to a head in Mecca. In 1511 the then governor Khair Beg saw coffee being drunk in a mosque as a preparation for a night vigil. In a fit of religious rage he drove the worshippers from the mosque and ordered all coffee houses in Mecca to be closed. The drinking of coffee was further condemned by two Persian doctors who resented the popularity of coffee as a local cure amongst melancholic patients, patients who might otherwise have visited their physicians. However the ‘mufti’ of Mecca argued for coffee. Finally the debate was resolved when the Sultan of Cairo intervened and reprimanded Khair Beg for unilaterally banning a drink which was widely enjoyed in Cairo without even consulting with his superior, and the very next year had him put to death on charges of embezzlement. Thus the coffee culture survived in Mecca.

Coffee - the global giant

The world coffee market today is vast, coffee being the world’s second most widely traded commodity after crude oil. World coffee production in 2004 is projected to be around 6.3 million metric tonnes, a reduction from 2003 figures due to stockpiling equivalent to 1.3 million tonnes. Ten years ago the global coffee economy was estimated to be worth some $30 billion, of which producers received $12 billion. Today it is worth around $50 billion with producers receiving a mere $8 billion of that (source Global Exchange, 2004). Brazil, Columbia and Vietnam are the world’s biggest coffee producers, accounting for around half of global production in 2001. Because of the central importance of coffee exports to their economies, a number of Latin American countries made arrangements before World War II to allocate export quotas so that each country would be assured a certain share of the US coffee market. The first such coffee quota agreement was arranged in 1940 and subsequent agreements were renegotiated in 1968, 1976, and 1983. However due to a shift in the balance of production, participating nations failed to sign a new pact in 1989 and world coffee prices have been in free-fall ever since as production continues to outstrip demand, and a “global coffee crisis” ensued. “Fair Trade” measures designed to help the struggling farmers only account for only 8 million of the 2.6 billion pounds, or 0.3% of the coffee sold annually in the USA. With an estimated 20 million coffee workers worldwide, developing nations have been hit hard by this global coffee crisis as trade prices have fallen short of production costs. New yield technologies in combination with overproduction, especially by the developing economies of Vietnam and the Ivory Coast, have largely contributed to the crisis. The human cost is demonstrable. In Latin America tens of thousands of farmers and labourers have begun migrating to look for alternative work as plantations close down. This is not the only toll of overproduction however, as the drive for cheaper, faster growing coffee has led to widespread clearance of the forest cover normally associated with high quality blends. In Vietnam alone, which produces around 11% of the world’s coffee, nearly 1.5 million acres are now under cultivation causing the clearance of vast areas of forest.

Who are the biggest coffee drinkers?

Just as there are big global producers, there are big global consumers, and all the coffee producing nations combined consume less than a quarter of what they produce. As one might expect, there are wide variations in domestic coffee consumption from one nation to the next. Germans consume around 7 kilos of coffee each a year, the Austrians 8, the Dutch 9, the Belgians 6, the Italians 5, the Danes 10, and the Swedes and Finns a mighty 11 kilos per person, well above the European Union average of 5 kilos per person. Americans and Canadians consume around 4.4 kilos each a year, and further down the scale the tea drinking Irish and British consume around 1.5 and 2.5 kilos per year per person respectively. Many major coffee producers such as Kenya, the Ivory Coast and Vietnam consume less than 0.2 kilos each a year domestically (International Coffee Organization 1997), suggesting that coffee is largely a cash crop. Europe in contrast consumes over a third of all world coffee production, and North America a fifth, although it is quite interesting to note that coffee consumption per person increases in more northerly climes and during the winter months.

What this translates to at the level of the US economy is 108 million coffee consumers spending an approximately $17.9 billion on coffee annually (SCAA 1999 Market Report). A quick calculation suggests that coffee drinkers spend on average $164.71 per year on their favourite stimulant. The National Coffee Association suggests that 54% of the adult population of the United States drink coffee daily and 25% occasionally (NCA, 2000). Among actual coffee drinkers the average consumption in the United States is around 3.1 cups of coffee per day. In comparison Italians consume 14 billion espresso coffees annually, and Italians consume approximately 3.7 kilos of coffee per capita and employ over 270,000 as “baristas”. The United States imports around 120 million kilos of coffee a month, the Germans 60 million, the Italians 30 million and the British 15 million. With all these facts and figures it is safe to assume that our coffee consumption has a major effect on our societies and economies. This can only have profound effects upon our health and behaviour, but what are the effects of coffee on our minds and bodies?

Coffee - a dark and potent elixir

People have enjoyed foods and beverages containing caffeine for thousands of years. It is perhaps one of the most well-studied substances we consume. Despite this strong controversy and debate continue. Coffee contains a complex mixture of substances, some of which are not affected by roasting. Other compounds, particularly those related to the aroma, are actually produced by partial destruction of the green bean during roasting. Some coffee substances do not evaporate and provide the rich, bitter taste, including caffeine, trigonelline, chlorogenic acid, phenolic acids, amino acids, carbohydrates, and minerals. Others provide the aroma, including organic acids, aldehydes, ketones, esters, amines, and mercaptans. Although caffeine exerts many physiological and psychological effects, there are many other active components within coffee which affect your mind and body. Of course it is caffeine, the alkaloid which comprises around 4% of the coffee bean which is its best known active ingredient. However, there are many members of the alkaloid family, including caffeine, theophylline, and theobromine, all of which are present in kola nuts, coffee, tea, cacao beans, mate and other plants. Although structurally related, these alkaloids have very different effects on the system, and are present in different amounts in different “medicinal” plants. For instance theobromine and theophylline, also present in tea and chocolate, relax the smooth muscles whereas caffeine stimulates the circulation, muscles and metabolism. Coffee is perhaps not best thought of as caffeine, as there are many other active substances which give coffee its unique range of medicinal actions.

After more than 19,000 scientific studies and centuries of human consumption, the safety of coffee and caffeine are still much debated, although the FDA still considers caffeine to be "generally recognized as safe". Such is our love affair with the “bean” that there are now countless claims that both caffeine and coffee are beneficial to human health. Medical institutions of reputation claim that drinking 2-4 cups of coffee a day may lower your risk of colon cancer by 25%, of gallstones by 45%, of liver cirrhosis by 80% and of Parkinson’s disease by 50% - 80%. No fewer than nine separate studies have shown that regular caffeinated coffee consumption may reduce the risk of Parkinson’s Disease by some 50%- 80% in both mice and men. Parkinson’s disease characterised by resting tremor or stiffness is caused by a reduced amount of dopamine in the motor centres of the brain, which caffeine may prevent or reverse. Coffee can even reduce the incidence of asthma by as much as 25% due to the presence of theophylline which relaxes the smooth muscle of the airways. Another feather in the cap of the coffee devotee is provided by research which suggests that there are four times the level of anti-oxidants in coffee than there are even in green tea. Coffee is also believed to be an effective anti-depressant, to have ergogenic (energy producing) properties and to improve memory. A cup of coffee contains an especially large quantity of anti-oxidant "polyphenols" such as chlorogenic acid (up to 8%) in its roasted form, whose strength is not diminished by decaffeination. Anti-oxidants are thought to counteract a number of degenerative diseases, including cardiovascular disease, cancer, cataracts, and disorders of the nervous system. Another anti-oxidant polyphenol called caffeic acid has also been found in coffee. Whilst the term anti-oxidant is much used it is seldom comprehended. Anti-oxidants, as their name suggests, have been found to effectively protect cells against oxidation (the addition of oxygen to molecules), which underlies the process of the slow internal burning within tissues that we commonly know as aging.

Indeed a veritable almanac exists for the purported health benefits of coffee, some of which are perhaps also worthy of mention. Just one cup of coffee, caffeinated or decaffeinated, helps prevent the formation of kidney stones by 10% possibly through its diuretic action in increasing the flow of urine and decreasing its concentration. Coffee is also alleged to reduce the risk of a number of cancers, most especially colon cancer (by 24% for four cups a day). Drinking coffee may even reduce your risk of developing type II diabetes, characterised by a loss of muscle, liver and fat cell sensitivity to insulin or by a reduced production of insulin by the pancreas. A study of 17,000 Dutch men and women suggested that those who drank seven or more cups of coffee a day were half as likely to develop the disease as those who drank two cups or fewer. Excellent news for the coffee industry, and also for heavy coffee drinkers, as scientists had previously suggested they were unusually sensitive to pain, prone to panic disorders and more likely to develop heart disease.

Caffeine - a wonder drug?

Caffeine is unquestionably the most widely used mood-altering drug in the world, and is regularly consumed by more than 80% of Americans. Although it is common knowledge that caffeine is a stimulant, what are the specific effects of caffeine on mind and body? Perhaps for convenience we should separate the actions of caffeine into psychological and physiological actions.

Caffeine stimulates the brain and spinal cord, and at ‘moderate’ doses enhances alertness, energy, motivation and concentration. Caffeine is a powerful psychostimulant, significantly increasing cognitive (understanding & reasoning) performance, and has also been found to improve the perception of well-being in individuals deprived of sleep for two days. Coffee is used relieve both normal and tension headaches, which are characterised by the dilation (widening) of blood vessels around the skull, often in combination with a painkiller like aspirin or ibuprofen. Caffeine is also widely used in the treatment of migraine in combination with an ergot alkaloid. Its effectiveness is largely due to its actions in antagonising (countering) the effects of the brain transmitter adenosine. Adenosine is an important modulator of brain activity, possessing sedative (calming), anxiolytic (anxiety dissolving), and anti-convulsant properties. Adenosine also dilates blood vessels in cerebral and coronary circulatory networks, a cause of many headaches, whilst caffeine produces the opposite effect, constricting the blood vessels. Indeed chronic caffeine exposure has been shown to increase the number of adenosine receptors in the brain, and explains why adenosine activity increases with coffee consumption, and why abrupt withdrawal from coffee consumption causes tension headaches. Another possible explanation for the potent psychostimulant effects of caffeine is because it enhances the release of the brain’s natural excitatory transmitters such as glutamate and aspartate. Indeed, in our hands a physiological dose of caffeine stimulated an almost 200% increase in the release of glutamate from nerve terminals in the hippocampus, a region of the brain involved in learning and memory.

Brain imaging studies confirm that a caffeine dose of 200 milligrams decreases blood flow through the brain by a third within an hour of administration, most likely by affecting adenosine receptor activity. Given that the average daily dose of caffeine in the United States (slightly more than two cups of coffee per person) is around 238 milligrams, this is likely a typical response. Indeed so profound are the effects of caffeine on adenosine receptors that habitual users show altered patterns of blood perfusion in their brains, so “the more caffeine you drink on a regular basis, the higher your cerebral blood flow will be when you do not consume caffeine" according to researchers. Caffeine reduces brain blood flow in the grey matter by about 26% in heavy coffee drinkers and by 19% in lighter drinkers. The image inset shows an FMRI image demonstrating activation of a structure associated with fear and anxiety called the amygdala in response to the infusion of caffeine.

Researchers have found that consuming coffee and caffeine has little or no harmful effect on exercise performance in healthy people, or in those with cardiovascular disease. Although caffeine has a mild diuretic action (promoting water loss through the kidneys through urine), there is no evidence that caffeine consumption causes a fluid-electrolyte imbalance that is harmful to health or to exercise performance. Recent studies on caffeine and dehydration concluded that drinking between one and four cups of coffee a day does not cause significant dehydration, although consuming greater quantities (5-6 cups of coffee a day) substantially increases urine production which may lead dehydration, especially during heavy exercise or in hot weather.

Although caffeine is not an appetite suppressant, it has profound effects upon the metabolism and may even aid weight loss. Caffeine increases the level of circulating fatty acids, which in turn increases the oxidation of these fuels to release energy, thereby promoting fat loss. This is probably why caffeine has been used by runners and endurance athletes for years to enhance fatty acid metabolism and endurance, as fat stores provide an abundance of energy, although caffeine appears more effective in those who are not habitual coffee drinkers. Many studies have suggested that caffeine has a positive effect on exercise performance, by increasing both energy and endurance, so much so that it is on the current list of drugs banned by the International Olympic Committee. There are additional mechanisms by which caffeine enhances performance. It increases circulating adrenaline (epinephrine) levels, increasing both the rate and output of the heart, and also increases the resistance of blood vessels to the flow of blood by constricting them (increasing blood pressure and therefore blood supply to the muscles). Caffeine also increases the force of muscular contraction during low-frequency stimulation by enhancing the release of calcium from its cellular stores, calcium being the trigger for muscle contractions. Caffeine also increases the metabolism of energy rich fatty acids and thus spares precious muscle glycogen stories, explaining its so-called ‘ergogenic’ (energy producing) properties and increased endurance associated with caffeine intake. So perhaps the Ethiopian hunters were right in eating coffee beans wrapped in animal fat all those years ago.

But it’s not all good news for coffee drinkers. Caffeine has many side effects, especially at high concentrations. Caffeine may inhibit the protective activity of common anti-epileptic drugs and has been shown to raise the level of lactate, a substance known to produce panic attacks. Some of coffee's components have a mild oestrogen-like effect on the body, worsening the oestrogen-dependent symptoms of premenstrual syndrome, which include tension, irritability, anxiety, fatigue and sleep disturbance. Indeed caffeine may be the single biggest cause of anxiety within our society.

Although the American Institute of Cancer Research and the World Cancer Research Fund have concluded that "Most evidence suggests that regular consumption of coffee and/or tea has no significant relationship with the risk of cancer of any site”. Caffeine is but one of many recognised carcinogens (cancer causing compounds) found in coffee, many of which are produced by the roasting process itself. As might be expected, studies linking coffee consumption with a higher incidence in cancers of the pancreas, ovaries, bladder, and kidneys in coffee drinkers are hotly debated.

There is great dispute as to whether caffeine or coffee causes or worsens the symptoms of heart disease and hypertension. One study suggested that there is an increased risk of developing hypertension associated with drinking five or more cups of coffee per day over a long period of time (over 33 years, 2002). However the prestigious Framingham Heart and Harvard University studies found that caffeine intake does not "appreciably increase the risk of coronary heart disease or stroke". Although it is generally accepted that caffeine does cause a short-lived increase in blood pressure, this only lasts for a few hours and is generally less than that normally experienced when climbing a set of stairs. However even a single dose of caffeinated coffee can increase intraocular pressure in people with glaucoma, a vascular disease of the eye associated with diabetes.

Caffeine raises levels of both adrenaline and cortisol, two of the body’s primary stress hormones from the adrenal gland. Indeed heavy coffee consumption can cause adrenal gland exhaustion, leading to adrenal “insufficiency”, a condition where the adrenal glands are unable to release enough adrenaline in response to stress. Adrenal insufficiency may lead to a weakened immune response and anxiety or panic attacks. In combination with increases in cortisol, which increases blood pressure by causing blood vessels to constrict and by increasing the contractile force of the heart’s pumping mechanism, large amounts of coffee may lead to a worsening of the symptoms of people with high blood pressure. Caffeine may not be good news for fertility either. Researchers suggest that women who drink more than one cup a day have a reduced likelihood of conceiving by 50%, and men who drink two or more cups of coffee a day have an increased incidence of abnormal sperm, and those who consume larger amounts often have sperm with reduced motility.

It is perhaps common knowledge that coffee decreases the quality of sleep and is one of the major causes of sleep disturbance. People suffering from insomnia often have elevated caffeine levels when compared to those of normal sleepers, and often as much as 40% of the caffeine they consumed in the morning is still in their system at bedtime due to its slow metabolism within the body. Foetuses and newborn babies are unable to metabolize caffeine in their livers, so it remains in their bodies for up to four days, stimulating their nervous system for the entire period, promoting irritability and difficulty in sleeping.

Of course at the other end of the scale a dose of more than 250 milligrammes (around three cups at once) at one time is necessary to cause symptoms of caffeine intoxication syndrome, whose features include restlessness, nervousness, excitement, insomnia, flushing of the cheeks, diuresis, gastrointestinal disturbance, muscle twitching, disordered thought and speech, tachycardia (increased heart rate), cardiac arrhythmia and periods of inexhaustibility. Given our love affair with caffeine and its presence in many foods and beverages including tea, soft drinks, chocolate and its availability in tablet form, perhaps one or two of us might feel a little uncomfortable when presented with this list.

Is coffee really addictive?

As if there were not already enough disagreement within the great coffee debate, we cannot leave a discussion of the effects of coffee on health without mentioning dependence and addiction. ‘Addiction’, to be technical for a moment, is defined as a strong dependence on a drug characterized by severe withdrawal symptoms, increased tolerance to a given dose (or the need for more and more of the substance), and the ‘drive’ to consume the substance regardless of an individual’s situation or environment.

Most psychiatrists do not feel that caffeine causes classical addiction, although withdrawal symptoms lasting a day or two may occur within ‘a small subset of individuals’. What’s more interesting is that at lower doses (one to three cups of coffee a day), caffeine has no demonstrable effect on the area of the brain involved with addiction, dependence and reward, thus acting in a different manner from classically addictive substances such as amphetamines, cocaine, morphine or nicotine. In fact it would take around seven cups of coffee drunk in rapid succession to trigger dopamine release within the nucleus accumbens region of the brain, which is believed to be the neurochemical basis of drug addiction.

However physical dependence upon caffeine has been clearly demonstrated in both human and animal studies, the most commonly occurring withdrawal symptoms being headache and fatigue. Other symptoms can include work impairment, mood changes and even flu-like symptoms with 24 hours of the last cup. These symptoms may last from two days to over a week, the incidence and severity of the withdrawal symptoms naturally increasing with previous levels of caffeine intake. There is even some evidence suggesting that caffeine withdrawal might disrupt academic performance or complex decision-making skills. However as with all drugs, dependence and withdrawal symptoms may vary considerably between individuals. Thus caffeine may be physically addictive but rarely does it appear to be psychologically addictive.

Finishing your cup

Perhaps no other recreational drug has had the positive impact that coffee has had upon our way of life and civilisation. Unlike other recreational drugs like alcohol, caffeine enhances rather than diminishes professional and social performance, and in contrast to other stimulants like amphetamines or cocaine, it is relatively inexpensive, freely available, is not strongly addictive and is nowhere near as neurotoxic. It is perhaps reasonable to argue that our society has become economically, socially and physiologically dependent upon the blackened bean, as few people abstain from coffee completely. Far fewer still consume no caffeinated beverages or foods. Coffee has overcome religious and trade disputes to become the global stimulant of choice, and even in societies where coffee consumption is relatively uncommon, other caffeine-rich plants such as tea, mate, kola nuts or cocoa are consumed. Thus society and its technologies have expanded with the use and prevalence of caffeine, as though humankind had developed a symbiotic relationship with this most stimulating of substances.