Nature's Pharmacopeia: A World of Medicinal Plants

Chapter 10



Coffea spp.


A traditional Turkish coffee service in Ürgüp, Turkey.

Coffee grows as a shrub or tree up to 5 meters in height (although it is usually pruned aggressively in plantation), with simple oval-shaped deep-green leaves and multiple flowers clustered at leaf bases on its branches.1 After fertilization, grape-size fruits develop containing two, or more rarely one, seeds (figure 10.1). Coffee plants arrive at maturity after about five years and continue to produce for another thirty-five years or more.2 The fruits (known as “berries”) are green when immature and turn to a deep red when ripe. The medicinal value of coffee is highest in the seeds (known as “beans”).3 The coffee plant originated in Africa, in the region that is now the highlands of Ethiopia, which is where people discovered its medicinal properties.4


FIGURE 10.1   Coffee (C. arabica): (top) plant; (bottom) mature berries. ([top] Photograph by Mark W. Skinner; USDA-NRCS PLANTS Database)

Until the twentieth century, most coffee production consisted of the species Coffea arabica, a variety growing best in the higher elevations (1000–2000 meters) and producing a beverage with a mild, complex flavor. In cultivation, C. arabica tends to be susceptible to pests, which reduces its yield. During the European conquest of Central Africa in the mid-nineteenth century, Westerners noticed natives chewing on the leaves of a novel species of coffee, C. canephora.5 C. canephora comes from the equatorial lowland (under 700 meters) forests of Africa and is thought to produce a bolder and harsher flavor than C. arabica.6 It also exhibits greater pest resistance than its highland cousin.


One of many legends relates that coffee was discovered by a goatherd named Kaldi, who lost his flock one day, only to rediscover the animals frolicking, dancing, and playing in a mountain forest. The source of their bizarrely energetic behavior, he reasoned, were the green leaves and red berries of the plants they had eaten. The next day, he again lost his goats to the coffee tree and decided to see for himself the effects of these plants. He chewed on some leaves and, although they were bitter, felt a pleasant stimulation through his body. He next tried one berry, then two. He enjoyed the slightly sweet pulp of the fruit and licked the seeds, which were covered with a tasty mucilage. Before too long, Kaldi joined his herd in gleeful, exuberant romping. Thus coffee became Ethiopia’s native stimulant, a source of energy and inspiration for dance and art.7


FIGURE 10.2   “Arbre du Café dessiné en Arabie sur le Naturel.” (Engraving from Jean de la Roque, Voyage de l’Arabie heureuse [1716]; Library of Congress, Rare Book and Special Collections Division, LC-USZ62-90572)

While the colorful myth of coffee’s discovery has not been borne out by archaeological or textual evidence, the plant’s fruits or seeds must certainly have been enjoyed by Ethiopians in the distant past, entered into commerce across the Red Sea to Yemen in the medieval era, and become known to the Arab and greater Islamic world (figure 10.2). As these early steps in the dissemination of coffee are far from clear, so too are the ways that coffee was first appreciated in Africa and the Middle East. In Ethiopia, people might have prepared the leaves and berries by steeping them in boiled water to make a coffee-flavored drink or ground the beans and mixed them with animal fat to eat as a snack. At some point, they also developed a coffee wine, made by fermenting the berry pulp, and a sweet drink of roasted coffee pulp in water, a tradition still observed in contemporary Ethiopia.8


FIGURE 10.3   Men preparing coffee in Gaza, 1870. (Photograph by Felix Bonfils)

The first written references to a plant identifiable as coffee indicate that its fruits and seeds were used medicinally as early as the ninth and tenth centuries.9 According to the Persian scholar Muhammad ibn Zakariya Razi (Rhazes, ca. 865–925), a plant called bunn and a drink made from it, called buncham, have hot and dry properties (in humoral medical terms) and are “very good for the stomach.”10 Later, the Persian physician Abu Ali al-Husayn ibn Abd Allah ibn Sina (Avicenna, 980–1037) wrote of bunn and buncham, declaring, “It fortifies the members, cleans the skin, and dries up the humidities that are under it, and gives an excellent smell to all the body.”11 Perhaps through a combination of commerce and the dissemination of medical scholarship, awareness of the coffee plant increased, and by the fifteenth century, someone (in Ethiopia or Yemen) had tried to roast and grind the beans to brew a dark beverage (figure 10.3).12

The practice of brewing coffee—the dark, bitter, stimulating beverage—seems to have become established most firmly in Yemen, where an Arab author of the mid-sixteenth century relates that “it drove away fatigue and lethargy, and brought to the body a certain sprightliness and vigor.”13 The Arabs called the coffee drink qahwa, the origin of the French café and the English “coffee.”14


FIGURE 10.4   Outdoor coffeehouses in the Ottoman style: (left) men smoking and drinking coffee at a coffeehouse near Cairo, Egypt; (right) a coffeehouse in Istanbul, Turkey. ([left] Louis Haghe, lithograph after David Roberts, The Coffee-Shop of Cairo [1849]; Wellcome Library, London, V0019182)

Arab adherents of the Sufi Muslim sect were among the first ritual coffee drinkers; they used the beverage to keep themselves awake for midnight prayers.15 While at first coffee was limited to spiritual-religious application (for its power over drowsiness), wealthy families eventually introduced coffee into their social gatherings, and merchants established coffeehouses for public use. Widespread commerce in the Arab and Muslim world during the late fifteenth and early sixteenth centuries brought coffee and coffeehouses from Yemen to Cairo, Damascus, and, in time, Istanbul.16 With the expansion of the coffee beverage followed the growth of an intellectually stimulating coffeehouse culture. In the cities of Arabia, Persia, North Africa, and the growing Ottoman Empire, the coffeehouse evolved into a place of free political thought, social bonding, and avant-garde discourse (figure 10.4). Such progressive thinking, however, frequently irritated the governing religious and political authorities.


In 1511, the governor of the Arabian city of Mecca grew wary of the unorthodox ideas emanating from his jurisdiction’s coffeehouses, and determined that coffee—like wine—was forbidden by the Qu’ran.17Consequently, he closed all of Mecca’s coffeehouses, a ban that lasted only until his coffee-drinking superior, the sultan of Cairo, heard about it and reversed the decree. (The official Cairo decree banned coffeehouses but permitted coffee drinking. In any case, efforts against coffee were only sporadically enforced, and coffee drinking continued both in secret and in the open.)18 Still, numerous regional governments and religious groups during this period placed restrictions on coffee and coffeehouses based on public safety, medical, and theological grounds, with little long-term effect.19 The lure of coffee remained strong, as the drink provided a medium around which people formed social and business connections, with a stimulating sense of well-being as a desirable side effect.

During the late sixteenth century, the coffeehouse culture blossomed in the large and multiethnic Ottoman Turkish city of Istanbul, and Turks grew to dominate coffee cultivation and model the coffee lifestyle.20The English philosopher Sir Francis Bacon (1561–1626) described an Ottoman coffeehouse in his posthumously published Sylva Sylvarum (1627), which illustrates coffee’s perceived roles in social life and physical health:

They have in Turkey, a Drinke called Coffa, made of a Berry of the same Name, as Blacke as Soot, and of a Strong Sent, but not Aromaticall; Which they take, beaten into Powder in Water, as Hot as they can Drinke it; And they take it, and sit in their Coffa-Houses, which are like our Tavernes. This Drinke comforteth the Braine, and Heart, and helpeth Digestion.21

The connection of coffee with Turkey is also important, as it was through the Turkish-controlled Middle East that African coffee first emerged as a world commodity.

Most coffee destined for Europe was shipped out of the Yemeni Red Sea port of Mocha to Suez and overland by camel to Alexandria on the Mediterranean for purchase by Venetian and French agents.22While European travelers and traders grew fond of coffee and coffeehouses, the Turks, who exerted authority over most of Arabia and North Africa at that time, maintained their monopoly on coffee cultivation by fiercely guarding against any export of coffee plants and steeping or partially roasting all beans destined for export to prevent subsequent germination.23

Yet by the seventeenth century, coffee growing and drinking had spread, with smugglers establishing plantations of Yemen-derived coffee in India and throughout the Dutch merchant colonial system. Cultivation was initiated in Java and the other East Indian islands of Sumatra, Celebes, Timor, and Bali beginning in the 1690s. In the eighteenth century, the French began growing coffee in their holdings in Martinique (1720), Haiti (1725), and Guadeloupe (1726), and the British and Spanish set up plantations in Jamaica (1730), Cuba (1748), and Puerto Rico (1755). Coffee also found its way to Portuguese Brazil (1727) via Suriname and French Guiana.24 Much of this vast diaspora of coffee originated with a handful of coffee plants smuggled out of the port of Mocha to the Dutch plantation in Java, two locations now firmly associated with coffee in modern parlance.25 Because this widespread dispersal came from a small number of parent plants, genetic diversity among much of the coffee (C. arabica) of the world is low, resulting in an increased susceptibility to a number of bacterial and fungal plant diseases.26

Coffeehouses flourished in the British domain and continental Europe during the seventeenth century. London and Oxford saw their first coffeehouses open in the 1650s.27 By 1663, more than eighty coffeehouses had opened in England, a number that increased to over 2000 by 1700.28 The first American coffeehouse was established in Boston in 1689, followed by one in New York in 1696.29 In Austria, many Viennese had their first taste of coffee following the retreat in 1683 of the Ottoman Turkish military, which had held an unsuccessful siege of the capital. The Turks left behind a considerable quantity of coffee beans, which the Viennese developed into a uniquely styled coffee.30 In Italy, Venice saw its first coffeehouse open in 1683, the first of many.31

The coffeehouse provided a venue for lively discussion and a brush with the exotic, a combination that certainly attracted the most progressive of society, including writers, artists, and statesmen. In the late 1680s, an Italian immigrant to France, François Procope, founded a coffeehouse, the Café Procope, across from the storied Comédie-Française (figure 10.5).32 The establishment drew the likes of the philosopher Jean-Jacques Rousseau, the playwright Voltaire, and the American statesmen Benjamin Franklin and Thomas Jefferson over the course of the following century.

In England, coffeehouses became important venues for social intercourse. Unlike alehouses, where drinking turned boisterous and uncivilized, coffeehouses allowed patrons to engage in erudite discussions—spurring some to call them “penny universities”—and to pursue business agreements.33 For example, the mammoth British insurance firm Lloyd’s of London originated as a coffeehouse where merchant mariners met to obtain insurance coverage for their cargoes.34

By the late eighteenth century, much of the world’s coffee was no longer grown in the Middle East. Instead, the bulk of coffee originated in extensive plantations under European control in Asia, South America, and the Caribbean. To harvest and process so much coffee, Europeans required a large workforce of cheap laborers. The plantations in the French colony of Haiti supplied half of the world’s coffee in 1788 and were tended by a huge number of African slaves living in the most inhumane of conditions. The slaves of Haiti led a long, bloody, but ultimately successful revolt against the French in 1791, and in the process they destroyed the hated plantations and murdered their former masters.35 The Dutch filled the global coffee shortage with exports from its Java plantations, tended by enslaved Javanese. During the mid-nineteenth century, Portuguese landowning nobles in Brazil enhanced production with new slash-and-burn plantations established at the expense of tropical rain forest and worked by millions of African and native slaves.36 In Guatemala and Nicaragua, coffee was cultivated during the nineteenth century through the forced labor of Mayan men, women, and children.37 All this increased production fed the intense and growing coffee habits of Americans and Europeans.


FIGURE 10.5   European coffeehouses were establishments of civil social interaction, as was Café Procope in eighteenth-century Paris. (Wellcome Library, London, V0014353)


While coffee became a premier social drink in Europe, its medicinal use was alternatively upheld and questioned by various sources. To Arab physicians of the sixteenth century, there was a disagreement on the subject of its humoral properties: some scholars claimed that the seed and fruit were cold and dry; others held that the seed and fruit were hot and dry or that the seed was cold while the fruit was hot.38 Coffee was generally thought to be good to dry up phlegmatic coughs and colds (by those who held to the hot-dry interpretation), a potent diuretic (and therefore good for the kidneys), and an effective hunger suppressor, but in excess it was blamed for causing hemorrhoids and headaches. The diuretic property of coffee was not universally appreciated as a benefit. For example, the author of a medical treatise of the era warns that an increased level of urinary excretion weakens the body. Other benefits of coffee documented by Arab authorities during this period include the treatment of “boiling (or bubbling) of the blood” and prevention of “smallpox, measles, and bloody skin eruptions.”39 The contention surrounding coffee’s health effects spread with the beverage itself to Europe and around the coffee-drinking world.

In 1610, the British poet George Sandys (1577–1644) visited Istanbul and noted that the Turks sat “chatting most of the day” over cups of coffee, which he found “black as soote, and tasting not much unlike it.”40 He also found anecdotal evidence of coffee’s medicinal value: “[I]t helpeth, as they say, digestion, and procureth alacrity [energy and liveliness].”41 In 1632, an English writer claimed that coffee could “mend” the temperament, with the capacity to “expell feare and sorrow, and to exhilarate the mind.”42 By the mid-seventeenth century, coffee found its way formally into the European pharmacopeia, being described by the herbalist John Parkinson (1567–1650) as strengthening the stomach, improving digestion, and treating tumors and blockages of the liver and spleen.43 To some, coffee’s possible health benefits placed it squarely in the category of panacea, as witnessed by the wide-ranging descriptions offered by especially ardent promoters. For example, London’s Rainbow Coffee-House on Fleet Street recommended coffee for conditions ranging from sore eyes to scurvy to the king’s evil (scrofula, a bacterial infection).44 The London coffee merchant Pasqua Rosee claimed that coffee could aid digestion, treat headaches and dropsy, prevent miscarriages, and cure a host of other ailments.45

Meanwhile, a number of voices emerged to warn of coffee’s possible deleterious effects. For example, the German physician Simon Paulli (1603–1680), following a line of argument common in his era, wrote that coffee “surprisingly effeminates both the Minds and the Bodies of Persians,” to the degree that men become infertile,46 while a French physician claimed in the 1770s that coffee was responsible for nymphomania.47 Although the seventeenth-century physician Thomas Willis (1621–1675) recommended coffee for its stimulating properties, he also warned that it could cause headaches, vertigo, and heart palpitations and could harm the joints.48 After the opening of a coffeehouse in Marseille in the late seventeenth century, a group of local physicians protested, claiming that the drink would “burn up the blood,” induce tremors, cause impotence, and lead to leanness.49 Through most of the seventeenth and eighteenth centuries, there was no consensus on whether coffee was a healthful drink or a toxic substance.

While the perceptions of the medicinal value of coffee were mixed for several centuries after its introduction into Western commerce, coffee in the nineteenth century faced stronger criticism for its perceived negative health effects. Some of these attacks were deserved: unscrupulous wholesalers sometimes adulterated cheap unroasted coffee with lead- and arsenic-based coloring agents to produce the uniform yellow or green hue attractive to buyers. In 1884, a headline in the New York Times warned, poison in every cup of coffee.50 During the late nineteenth century, the health lifestyle entrepreneur C. W. Post (1854–1914) railed against the American coffee habit, suggesting in ubiquitous advertisements that people switch to his grain-based coffee substitute, Postum, and breakfast cereal, Grape-Nuts, for a more hearty diet. “You can recover from any ordinary disease,” he said, “by discontinuing coffee and poor food, and using Postum Food Coffee.” Post’s attacks on coffee continued: “Coffee frequently produces indigestion and causes functional disturbances of the nervous system,” and “Coffee is an alkaloid poison and a certain disintegrator of brain tissues.”51 While Post made his claims in the absence of any medical authority, a number of doctors joined Post’s cause and warned of the myriad dangers of coffee. Indeed, coffee’s perceived wholesomeness suffered during the first two decades of the twentieth century.

Despite the efforts of health evangelist businessmen such as Post, the prohibition of alcohol in the United States during the 1920s boosted coffee’s place as the national social drink.52 Coffeehouses again proliferated, and home consumption of the beverage increased. By 1923, American demand accounted for half of the world’s coffee.53 During the 1940s, the Allied war effort combated cold and fatigue with coffee, both in the battle zones and on the home front. After the war, coffee maintained its place in homes, restaurants, and offices as a social and economic fuel for the post–World War II age. While mainstream American tastes had grown accustomed to mild-flavored blends of beans and a brewing process that recirculated coffee over spent grounds, some spirited entrepreneurs saw an opportunity to redefine coffee and the coffeehouse.


During the decades following the 1950s, a number of coffee merchants began to specialize in selling select blends of coffee and developing coffeehouses that brewed elite beans into strong, highly flavorful drinks. Alfred Peet (1920–2007), a San Francisco–based coffee importer, established Peet’s Coffee & Tea in Berkeley in 1966.54 A few years later, three Seattle entrepreneurs visited Alfred Peet and trained to select, roast, grind, and brew coffee in his shop. They returned to Seattle and opened their own coffeehouse, Starbucks, in 1971.55 The renewed interest in American coffeehouses combined an emphasis on quality coffee beans and strongly flavored coffee served in an environment conducive to social gathering. Serving much the same role in modern times as the coffeehouses of seventeenth-century Europe, the establishments of the twentieth and twenty-first centuries helped engage people in conversation over stimulating cups. During the 1990s and 2000s, the Starbucks operation grew enormously, generating a worldwide footprint of American coffeehouse culture with more than 20,000 locations.56 Indeed, the explosion of coffeehouses on the American model, including corporate and independent firms, based in the United States or internationally, is in essence a recapitulation of manifested practices of earlier generations and other places, from Mecca and Istanbul to London and Paris.


Much of the success of the premium or specialty coffee shops is attributable to the selection and processing of the beans, which has a key role in the ultimate flavor of the drink. Before 1900, nearly all coffee consisted of the species C. arabica, which grows best in cool tropical highlands that receive steady rain throughout the year.57 The beans contain about 1 to 1.5 percent of the stimulant compound caffeine and generate a highly flavorful brew.58 However, C. arabica yields are sensitive to frost, and the plants are susceptible to the fungal pathogen coffee rust (Hemileia vastatrix).59 C. canephora, a variety brought into cultivation from the Congo in 1898, grows acceptably in a wider geographic range and produces beans with slightly more caffeine than C. arabica and a harsher flavor.60 It is more resilient against fungi than C. arabica and thus is grown widely and used in blending, particularly for cheaper or instant coffees.61

Most coffee berries grow with two seeds (beans), although a fraction of them (perhaps 5 or 10 percent) have a single seed. These rare, single-seeded coffee fruits are known as peaberries and are thought to produce a particularly richly flavored coffee.62 The coffee berries are harvested when their color turns from green to red.63 To remove the seeds from the berries, producers historically used one of two methods. The dry method consists of stripping berries from the trees and allowing them to dry on tarps under the sun. After frequent spreading and turning, while protecting from dew and any other moisture, the fruits shrivel and harden. The dried husks can be removed by pounding on them, yielding the seeds. Today, much of the drying and husk removal is done by machine. The wet method, developed in the West Indies and used throughout Central America, requires harvesting the ripe berries, removing much of the pulp, and allowing any remaining material adhering to the bean to soak and ferment in large tanks of water for up to forty-eight hours. Then, the softened tissues are washed off with running water and the beans dried under the sun or by machine.64 The wet process is thought to impart a more nuanced flavor to the seeds but has also been responsible for a tremendous amount of water pollution: waste coffee pulp was discharged into streams and rivers, ultimately choking these waterways of oxygen as the organic material decomposed. However, recent ecologically conscious practices, such as retaining coffee pulp as natural compost, have improved the quality of water in places such as Guatemala and added value to former waste products.65


FIGURE 10.6   Green coffee beans (top) and green peaberries (bottom).

Raw coffee beans are known as green beans, although their color can range from green to yellow, white, or tan (figure 10.6). Coffee beans may be blended from different sources to produce a mix of flavors or characteristics deemed desirable for the consumer. The roasting process also can add new flavors to the beans. A lighter roast is generally preferred in the United States, through which the beans are subjected to a temperature of 212 to 218° Celsius until they turn a uniform brown color. During the roasting process, the starches in the coffee bean turn to sugars at about 207°C and caramelize above 212°. At 238°, the caramelized sugars begin to burn. Therefore, the lighter roasts bring out more sweetness in the coffee; a darker roast imparts less mild flavors. A Vienna roast takes place at temperatures around 240°, and the French roast occurs at 250°.66 Once roasted and ground to a fine powder, coffee has a very short shelf life before losing robustness and aroma, which is why most drinkers prefer a fresh grind.



Caffeine Content



Brewed coffee

74–83 mg/5-oz. cup

Decaffeinated coffee

2–3 mg/5-oz. cup


24–30 mg/5-oz. cup


4–5 mg/5-oz. cup

Regular or diet colas

26–58 mg/12-oz. serving

Caffeine-free colas

0 mg



Milk or sweet chocolate

6–20 mg/oz.

Baking chocolate

35–60 mg/oz.



Anacin, regular strength

32 mg/tablet

Excedrin, extra strength

65 mg/tablet



No Doz

100 mg/tablet


200 mg/tablet

Source: Jerrold Meyer and Linda Quenzer, Psychopharmacology: Drugs, the Brain, and Behavior, 3rd ed. (Sunderland, Mass.: Sinauer, 2013).


The stimulating property of coffee derives from its active principle, caffeine. First isolated from coffee in 1819 by the German chemist Friedlieb Runge (1795–1867), caffeine is responsible for many of the behavioral and physiological effects of coffee, tea, and other medicinal plants (figure 10.7).67 Caffeine usually enters the bloodstream within thirty to sixty minutes of oral consumption, beginning through the stomach and continuing through the small intestine.68 In low doses (100 milligrams, for example), caffeine produces subjective effects such as enhancement of alertness and reduction in tension as well as mild euphoria and improved sociability and self-confidence. At higher doses (200 milligrams or more), some people experience tension and anxiety. At very high doses (twelve or more cups of coffee per day; 1.5 grams of caffeine), caffeine causes agitation, tremors, and insomnia. The lethal dose of caffeine is about 10 grams (approximately 100 cups of coffee).69


FIGURE 10.7   Caffeine.

Caffeine likely acts by blocking the receptors for the neurotransmitter-like chemical adenosine, which is normally involved in promoting calm and sleepiness.70 Therefore, as an adenosine antagonist, caffeine hinders the ability of the brain to feel sleepy, resulting in alertness, increased cognitive performance, and anxiety.71 Adenosine inhibits dopamine signaling, and since one type of adenosine receptor is especially concentrated in the striatum, a part of the brain rich in dopaminergic neurons, the blockade of adenosine function by caffeine is thought to stimulate a low level of dopamine signaling in this region, giving a mild sense of well-being without intensely activating the reward center of the limbic system.72

Caffeine consumption results in increased heart rate, blood pressure, and respiration both through antagonism of the adenosine system and through the stimulation of epinephrine release.73 It dilates the coronary arteries but has the opposite effect on blood vessels in the brain, which it constricts, thus in some people relieving headaches. Caffeine is frequently added to over-the-counter analgesics containing aspirin or acetominophen as it enhances their efficacy against pain.74 Caffeine also relaxes the bronchial passages and increases urine output.75


Increase in mental alertness



Slight increase in heart rate

Dilation of coronary arteries

Constriction of cerebral arteries


Increase in urine production

Among heavy users, caffeine consumption during pregnancy is associated with an increased risk of spontaneous abortion and stillbirth. While caffeine is not a teratogen, antagonism of the adenosine system in the developing fetus is suspected of causing harm. However, recent investigations of any relationship between caffeine intake and perinatal outcomes have generated contradictory findings.76 Unfortunately, many of the studies on caffeine and fetal health have been conducted improperly, with biased sample populations and poor controls. Still, many researchers recommend moderating caffeine use during pregnancy as a precaution.77 In light of the concern over potentially damaging effects of caffeine during pregnancy, it is interesting that caffeine and closely related compounds can be employed therapeutically to treat apnea in prematurely born infants.78

Humans develop tolerance to caffeine and can become physically dependent.79 Tolerance manifests as a reduced level of stimulation over time following ingestion of the same amount of caffeine and includes a lower effect of caffeine on tension, anxiety, blood pressure, heart rate, and urine production.80 As a result, some users increase their caffeine use to produce the same physiological outcome. Among regular consumers, cessation of caffeine produces an array of typical withdrawal symptoms, including headache, irritability, fatigue, and poor mood, which usually last no more than a day or two.81

From its origins in eastern Africa to a place in the daily rituals of millions of people worldwide, coffee has melded into human life. Economies are built on its commerce, and workers, artists, and students alike are fueled by its stimulating effects. Few would argue that coffee—charged with its potent constituent, caffeine—is dispensable in the modern age. A beverage that ties together social groups, improves mental activities, and promotes scholarship and discourse is a remarkable type of medicine.