The World of Caffeine (60 page)

Everyone knows that scientists investigate the world by systematically testing hypotheses using carefully designed experiments. The results of their studies are presumably replicable and therefore their conclusions represent objective advances in scientific understanding. Unfortunately, in the area of human health, the complexity of the human body and mind and the inability of investigators to conduct potentially dangerous experiments on human beings as part of their research often make it difficult to make reliable judgments. There are three potential weaknesses of medical studies that pose problems for those seeking to understand caffeine’s health effects: biased sample selection, inaccurately measured exposure, and failure to exclude confounding variables. Because these limitations can be seen most clearly in studies of caffeine’s effects on the outcomes of pregnancy, it is valuable to examine in detail some of the methodological problems that bedevil scientists working on these questions. While reading this section, however, the reader should keep in mind that similar or identical problems attend investigations of every area of caffeine and human health discussed in this book.
¹

Studies of the effects of caffeine consumption on reproductive hazards, including the risk of delayed conception, spontaneous abortion, prematurity, low birthweight, and major congenital malformations, multiplied like rabbits throughout the 1980s and 1990s. Although poor design has limited the value of many of them, the larger, more probative studies generally demonstrate no correlation between caffeine use and reproductive hazards of all kinds.
²
Yet, as is true for the results of any epidemiological studies, the value and weight of their conclusions depend on whether the people studied were selected in a way that did not prejudice or distort the outcomes.

Unfortunately, defective sample selection is endemic to studies of caffeine and human reproduction, in part because few researchers into reproductive hazards undertake studies with caffeine or coffee as their primary initial interest. Many even inquire about caffeine use only to divert attention from questions about other risk factors such as cigarettes and alcohol. Such casual treatment of caffeine is possible— and especially distressing—only because caffeine is so much a part of life that it is little noticed and then often only as an afterthought.

It is evident that an accurate assessment of exposure, that is, the amount of caffeine consumed, is fundamental to any evaluation of a link between caffeine consumption and health. In fact, precision in measuring exposure is essential, because a dose-response relationship—that is, the tendency of increasing doses to elicit increasing responses—strongly suggests a causal relationship and cannot be evaluated without it. If a low exposure is correlated with low risk, moderate exposure with moderate risk, and high exposure with high risk, scientists are more inclined to posit a corresponding cause-and-effect connection. In the matter of adverse effects on pregnancy, such a relationship would exist if those pregnant women who consume more caffeine were at a higher risk for adverse effects than pregnant women who consume less, and it would lead us to think that caffeine exposure is the cause for these untoward outcomes.

Laboratory control studies rely on a number of stratagems, such as using decaffeinated coffee to which varying doses of caffeine have been added, to enable the researchers to record the exact amount of caffeine consumed. For epidemiologists, scientists who study the occurrence and causes of diseases in the field, however, it is rarely a simple matter to determine how much caffeine subjects have used. Tea and coffee cups commonly range from four to sixteen ounces.
³
So long as estimates of caffeine consumption are tied to coffee drinking, the wide variability of caffeine content in the beans and of roasting and brewing methods, which reflect regional variations and personal preferences, will limit the ability of epidemiologists to determine the actual levels of caffeine consumption. An additional problem is the unreliability of questionnaire answers, which may underestimate or overestimate intake. For example, in a recent breast cancer study in which records of caffeine consumption were kept and compared with later recollections of that consumption, it was found that the women studied reported an average of 75 mg a day less caffeine than they had actually ingested, while the women serving as controls underreported their
consumption by only 40 mg a day.
⁴
In another study, pregnant controls were more likely to underreport consumption than women who had miscarried.
⁵
In any case, serum concentrations of caffeine’s primary metabolites, such as paraxanthine, do not closely correspond with questionnaire answers about caffeine consumption. Discrepancies may reflect errors in recollection, varying methods of preparation, or differences in metabolic degradation rates. It is evident that, to accurately gauge caffeine exposure, future researchers must utilize not only questionnaires and cup counts, but biomarkers—that is, objective measures of caffeine and its metabolites in the body—as well.

Measuring exposure to the fetus is especially difficult because the amount of caffeine consumed and the speed at which it is metabolized vary throughout pregnancy. For example, because of the nausea associated with the first six months of pregnancy, consumption may be lower than usual during that period. Another confusing factor is that it takes longer for the body to get rid of caffeine’s metabolites near the end of pregnancy.
⁶
Therefore, to avoid the unpleasant feelings associated with elevated blood levels of caffeine’s metabolites, some women appear to reduce their consumption of caffeinated drinks during pregnancy.

A different sort of problem arises when exposure to caffeine is measured but effects of exposure to other drugs that may have been consumed along with it are overlooked. Yet another confounding exposure may arise from neglect of non-dietary sources of caffeine, such as over-the-counter and prescription medicines that people may not realize contain caffeinated and so fail to report.

We have already noted ways in which hidden variables can baffle attempts to understand the relationship between the use of caffeine and any given health outcome. Epidemiologists call such variables “confounders” that, according to one researcher, “plague the literature” about the link between caffeine and problems in human reproduction. An example is the confounding variable of maternal age. Coffee consumption tends to increase with age throughout the childbearing years and, at the same time, the risk of many reproductive hazards also increases with age past 25 or 30.
⁷

People who drink coffee differ in significant ways—over and beyond their use of coffee—from those who do not, and those who drink a great deal of coffee differ from those who drink less. Comparisons of health effects are particularly problematic between members of these groups and people who do not use caffeine with respect to any health-related variable.
⁸
An example of material confusion results from the fact that people who drink little or no coffee tend to use less tobacco and alcohol than those who are heavy coffee drinkers. This kind of insidious confounder can easily engender false claims of a causal connection between coffee or caffeine and health problems.
⁹

1
. Henry Watts, ed.,
Dictionary of Chemistry,
vol. I, p. 707.

2
. John Evelyn,
Works,
note, p. 11.

3
. Sir Richard Steele,
Tatler,
April 12, 1709.

1
. Johann Wolfgang von Goethe,
Versuch die Metamorphose der Pflanzen zu erklären (Attempts to Illustrate the Metamorphosis of
Plants).
In this book Goethe takes his place as a pioneer in the theory of evolution.

2
. As P.Walden, in his essay “Goethe and Chemistry,” states, “At Weimar the time had come for Goethe to reexamine his chemical knowledge and concepts, to transfer them into the realm of practice and reality, simultaneously, however, to give them a more solid theoretical foundation” (George Urdang,
Goethe and Pharmacy,
p. 15).

3
. Fielding H.Garrison,
History of Medicine,
p. 262.

4
. The singular distinction of Goethe’s fame is that the paradigm of the widely celebrated writer began with him. Before Goethe, the authors of important books had enjoyed respect, but they had never become personal heroes to a large public. Although their works were honored, the authors themselves were uninteresting to the popular imagination. But from the time his early novel
The Sorrows of
Young Werther
instigated suicides among teenagers across Europe, people everywhere became what we would today call Goethe’s “fans.”

5
. Wolfgang von Goethe,
The Sorrows of Young Werther,
p. ix.

6
. Berthold Anft, “Friedlieb Ferdinand Runge,” p. 574.

7
. It is the use of “sleepy substance” as an explanatory mechanism for morphine that Molière makes fun of in the
Imaginary Invalid
and that Nietzsche cites as typifying the silliness of the empiricists’ arbitrary reifications.

8
. We regret our inability to determine the first names of some of the scientists mentioned in our book.

1
. Dr. William Adams, professor at the University of Kentucky and author of
Nubia,
told us in an interview in 1997, “There is absolutely no evidence, textual or archaelogical, of any use of coffee in Nubia or Abyssinia before modern times.”

2
. For example, we have no accounts from the Crusaders (c. 1100–1300) that mention encounters with coffee.

3
. Reverend Doctor J.Lewis Krapf,
Travels, Researches and Missionary Labours During Eighteen Years Residence in Eastern Africa,
p. 47.

4
. James Bruce,
Travels to Discover the Source of the Nile.

5
. Perhaps, in addition to knowledge of the plant, the prerequisite for the spread of coffee is the discovery of the methods of roasting and infusing the bean. People seem to have entertained a limited inclination to chew the fruit, even when it had been kneaded with lard or butter, and, although swilling heavily reboiled raw coffee and swallowing the grounds gained a little more acceptance, roasting and infusion were the watershed inventions that transformed coffee from a rank medicinal powder or murky sedimented syrup into a beverage coveted for its flavor as well as its stimulating effects. Yet, in the end, even this answer does not completely resolve the mystery, because the flesh of the coffee berry is fragrant and good tasting and fully charged with caffeine. In fact, its apparent appeal adds a puzzle: Why did the use of the bean spread, despite the dislike expressed by so many for its taste, while the eating of the pleasant fruit remained a localized curiosity?

6
. William Ukers,
All about Coffee,
p. 8, quoting from Dufour’s translation.

7
. Lenn E. Goodman,
Avicenna,
p. 36.

8
. Ulla Heise,
Coffee and Coffee-Houses,
p. 11, quoting Liber canonis, Tractatus secundus, 1608, chapter 90.

9
. Ukers,
All about Coffee,
p. 8.

10
. William Gohlman,
The Life of Ibn Sina,
p. 36. Also see Goodman,
Avicenna,
p. 45, n. 13. The value of this resource, afterward destroyed by Suni zealots opposed to the Sultan’s Shiite sympathies, should not be underestimated. In later life, Avicenna recalls rooms full of books dedicated to each subject, ancient or modern, where he saw “books whose titles are unknown to many, and which I never saw before or since.”

11
. That a leading thinker such as Avicenna should have mentioned the coffee bean and described some of its properties only deepens the mystery of the absence of any further references for several hundred years.

12
. Ukers,
All about Coffee,
p. 8, quoting Leonhard Rauwolf,
Aigentliche beschreibung der Raisis so er vor diser zeit gegen auffgang inn
die morgenlaender vilbracht,
Lauingen, 1582–83.

13
. Giovanni Battista Montanus (1488–1551), Italian physician and classicist, tells us in his
Commentary
that Avicenna wrote the
Canon
“because he saw that neither the Greeks nor the Arabs had any book that would teach the art of medicine as an integrated subject.” See Nancy Siraisi,
Avicenna in Renaissance Italy,
p. 20. See also, Goodman,
Avicenna,
p. 47, n. 38.

14
. Anonymous editor,
Canon of Medicine,
“Introduction,” no page, found in the library of the University of Pennsylvania.

15
. Francis Ross Carpenter, in
The Classic of Tea,
p. 35, referencing Reinaud,
Relations des Voyage fait par les Arabes et les Persans
dans l’Inde et…la Chine,
I, 1845, p. 40.

16
.
The Odyssey,
translated by Samuel Butler, Book IV, lines 219–34. Pæeon was a celebrated physician, mentioned also by Virgil and Ovid, with a truly upscale practice. He treated the wounds which the gods received during the Trojan War. On his account, physicians were sometimes called
Poeeonii
and medicinal herbs
Poeeonoe herboe.

17
. Robert Fitzgerald aptly translates the phrase as “an anodyne.”

18
. Heinrich Eduard Jacob,
Coffee: The Epic of a Commodity,
p. 74, quoting Simon André Tissot,
Von der Gesundheit de Gelehrten,
Leipzig, 1769.

19
. Sir Henry Blount,
A Voyage into the Levant,
pp. 20–21.

20
. See John DeMers,
The Community Kitchen’s Complete Guide to Gourmet Coffee.

21
. Jacob,
Epic of a Commodity,
p. 44.

22
. The Arab legends of the first encounter with coffee, invariably set in Ethiopia or the Yemen, are often stocked with the full range of fabulous Oriental devices that are the mark of Islamic legends. One of these, an entry in the Omar cycle, is, in particular, worth our attention, and so begins
The Tale of Amorous Acolyte: A Giant Ghost, Swirling Water, a Beautiful Princess, and the Coffee Tree
In the year 656 A.H. the mollah Schadheli, making his holy pilgrimage to Mecca in the company of Omar, his disciple, came as far as the wilderness of Ousab, to the Emerald Mountain. At once, he knew he would go no further.
“It is the will of Allah, blessed be his Name, that this very night I should die on this mountain,” he told Omar. “When I am gone, a veiled personage will appear to you. Take care to obey his commands!” So saying, Schadheli entered the cave, lay upon a spread of cloth, and waited.
True to his word, as a religious man of honor, Schadheli died that night. Soon after, Omar, leaving the side of the body to refresh himself with the night air, was startled by a flash of light which, when his bedazzled eyes could again see, had left behind a giant spectre draped in a white veil. Summoning his courage, Omar demanded that the figure reveal his name. The phantom said nothing, but when he removed the veil, Omar recognized his late master, grown to height of thirty feet.
The giant visage stamped his foot on the rocky ground, splitting it, and a fountain of pure water burst from within the earth.
“Fill your bowl with water from this fountain,” the spirit told Omar, his ghostly form already fading against the black desert sky and the jewel-like stars. Then, just before vanishing, he added, “Carry the bowl towards Mocha while the water yet swirls!”
Omar turned southward and set out toward the famous port. After journeying for three days and nights without food or sleep, holding the bowl before him and glancing continually to see if the water still turned within, suddenly he noticed it had stopped moving. When he looked up he saw that he had arrived in Mocha, where he soon discovered the people were suffering greatly from a terrible plague. Omar’s prayers cured all who came before him. His reputation for healing spread quickly among the wise, reaching the ear of the vizier, a clever counselor to the Sultan. The Sultan, a trusting man, had a beautiful daughter whom he loved above all things and who lay as if dead within her chambers. He heeded his advisor by sending for the holy physician. Omar cured the girl and, entranced by her loveliness, made love to her as soon as she awoke.
With forbearance compelled by his gratitude for the city’s rescue, and with the encouragement of his vizier, to whom Omar had given an amatory talisman (which made him irresistible in love), the Sultan spared Omar’s life but exiled him back to the wilds of Ousab, where, as before, the holy man was left with only herbs for food and a cave for shelter.
Wearying of solitude and the barren waste, Omar cried out to his dead master, “Why have you sent me on this circular and ill-fated journey?” As if in response, a small green bird alighted in a nearby tree. When Omar came near, he saw the tree was covered with green leaves, small white flowers, and bright red fruit. He filled a basket with the berries, and later that night, when preparing to boil his dinner of herbs, he thought to break open the fruit and toss the seeds into the pot in their stead. The result, to his amazement and delight, was the aromatic and fortifying beverage we know today as coffee.
Others say that Omar’s master gave him a small wooden ball which rolled of its own as if alive, instructing him to scrabble after until it stopped moving. The ball led him to a village where he effected cures by dispensing the boiled red berries of a stand of wild coffee trees growing nearby.

23
. Ralph S. Hattox,
Coffee and Coffeehouses,
p. 15.

24
.
Ibid.,
p. 14.

25
.
Ibid.,
p. 74.

26
. The time of caffeine’s early proliferation was a turbulent one in the Yemen. The Pashas of San’a, who ruled the tiny domain, were appointed by either the sultan of Constantinople or the Ottoman Pasha in Cairo, depending on which of them had the upper hand that particular year. Until 1547, control of the Yemeni port city of Aden was contested between the Ottomans and the Portuguese, who had established bases on the Abyssinian side of the Red Sea. Although the Ottomans briefly succeeded in closing off trade from the area, within decades spices, especially pepper, were again reaching Egypt by way of the Yemen and the ports of the Hijaz. The imams, or local chiefs, enriched by trade and encouraged by ambitious Europeans, successfully contested Ottoman authority in San’a, so the spice traffic flourished again. This traffic was decisively and permanently rediverted only when the Dutch and English developed the Cape route to the East in the seventeenth century. Fortunately for the Yemen’s economic health, by that time coffee was already replacing spices as its most important item of trade. See Kamal S.Salibi,
A History of Arabia,
p. 150.

27
. Hattox,
Coffee and Coffeehouses,
p. 61.

28
. The
Bacchoe
is a play which, as William Arrowsmith comments in his introduction to his translation, is dimly reminiscent of the unsettling invasion of Hellas by the cult of Dionysus, an occurrence with obvious parallels to the advent of the coffeehouse culture in Islam.

29
. One interesting detail of the testimony was a physician’s assertion that Bengiazlah, a famous contemporary of Avicenna, had taught that, according to humoral theory, coffee must be regarded as “hot and dry,” not as unwholesomely “cold and dry,” as Beg’s witnesses claimed. Even at this early time, however, uncertainty prevailed about the meaning of the reference, and coffee’s opponents answered that Bengiazlah had not been speaking of coffee at all, but of a drink also known as “kahwe” but made from a different plant.

30
. Hattox,
Coffee and Coffeehouses,
p. 77.

31
. Such references are scattered throughout
Reis’ in die Morgenländer (Rauwolf’s Travels),
published at Frankfurt and Lauingen in 1582–83.

32
. Joseph Walsh,
Coffee: Its History, Classification, and Description,
p. 7.

33
.
Ibid.,
p. 6.

34
. Robert Nicol,
A Treatise on Coffee: its properties and the best mode of keeping and preparing it,
pp. 11–12.

35
. Maguelonne Toussaint-Samat,
History of Food,
p. 581.

36
. Walsh,
Coffee: Its History,
p. 7.

37
. Hattox,
Coffee and Coffeehouses,
p. 106, quoting Jaziri.

38
.
Ibid.,
p. 111, quoting Jaziri.

39
.
Ibid.,
p. 110, quoting Celibi.

40
. Ukers,
All about Coffee,
p. 30, quoting Jean La Roque,
Voyage de L’Arabie Heureuse,
Paris, 1716.

41
. Between 600 B.C. and A.D. 1900 the population of the Yemen remained almost constant at about 2.5 million. It was called, together with Oman,
Arabia Felix,
or “Fortunate Arabia” by the classical geographer Ptolemy. The Yemen’s moderate climate contrasts with that of the barren interior of the Arabian peninsula, which Ptolemy called
Arabia Deserta,
or “Desert Arabia,” and that of the Hijaz, which he called
Arabia Petroea,
or “Stony Arabia.” Although only 10 percent of the total area of the peninsula, the Yemen has consistently sustained about 50 percent of Arabia’s population since the introduction of agriculture in the third millennium B.C.
These circumstances have both isolated the Yemen and helped define its identity, making it a kind of oasis of activity, surrounded by the ocean on one side and desert on the other, relatively remote from the major capitals of the world.