The World of Caffeine (42 page)

Caffeine, a chemical sometimes called “theine,” “guaranine,” or “matein,” according to whether tea, guarana, or maté, rather than coffee, is regarded as its eponymous natural source, occurs in the nuts, berries, beans, seeds, pods, hulls, leaves, and barks of several dozen varieties of plants. Every year, more than 120,000 tons of caffeine are consumed worldwide, enough to spike 260 cups of coffee or tea per person per year, or about five cups a week for every man, woman, and child on earth. A little over half of this tonnage comes from coffee beans and a little less than half of it comes from tea leaves. The remaining tiny fraction comes mostly from cacao pods, and also from maté leaves, cola nuts, and a small residue from all other sources.
¹
(Because very little caffeine is synthesized in laboratories, we examine the provenance of caffeine exclusively in terms of its vegetable sources.)

Caffeine supplies people with a physical and mental boost. But why did plants evolve the ability to produce it? The answer is that caffeine provides plants with protection by killing harmful bacteria and fungi and causing sterility in certain destruc tive insects. Because, over the passage of years, caffeine permeates the surrounding soil, it may also inhibit the growth of weeds that might otherwise have choked the plants. Caffeine’s potent antibiotic, antifungal, pest-killing powers may explain why
Coffea robusta,
which produces a larger amount of the drug, is much hardier than its more delicate cousin,
Coffea arabica
.

Adapted from Spiller, p. 187.

However, in using caffeine as a biochemical weapon, plants are indeed “hoisted by their own petard,” because the very drug that helps them destroy their enemies ultimately kills them as well. Nature’s intricacy is again instanced in the mechanisms that caffeine-containing plants use in a doomed attempt to limit damage to themselves from caffeine’s poisonous effects. For example, coffee seedlings produce and store caffeine away from the site of cell division, which are very sensitive to toxins. Nevertheless, caffeine eventually devastates the plants that produced it, for as caffeine-bearing bushes or trees age and the soil around them becomes increasingly rich in caffeine absorbed from the accumulation of fallen leaves and berries, it eventually attains a level toxic not only to microbial enemies but to the plant itself as well. It is partially because of this toxicity that coffee plantations tend to degenerate after ten to twenty-five years. In a sense, these plants lose their lives as a result of steadily producing the drug that humanity loves best.

One of the first scientists to explore the theory that caffeine production evolved to protect plants from insects was Dr. James Nathanson, a neurologist at Harvard Medical School. In an article published in 1984 in
Science
magazine, Nathanson proposed that caffeine and related compounds could be used as the basis for a new class of insecticides.
²
His tests with powdered tea and coffee, as well as with chemically pure caffeine and other methylxanthines, found that these compounds interfered with the behavior and growth of many insects and insect larvae. Mosquito larvae drowned when they became so confused that they could not swim to the surface to breathe. Concentrated caffeine killed adult insects in hours or days after exposure. Caffeine also demonstrated a considerable synergistic killing power when combined with other natural insecticides, sometimes increasing the effectiveness of known agents by a factor of ten.

The neurotoxicity of caffeine as a natural chemical defense mechanism for plants against insects explains the discombobulation of the spiders enlisted for a recent NASA study of the ways exposure to various chemicals alters the ways they spin their webs.
³
Some scientists think that spider web testing can replace some much more expensive toxicity testing in humans or higher animals. The theory is that the changes in the spider webs are a function of the degree of toxicity of the chemical administered prior to spinning. The more deformed a web becomes, the more toxic the chemical is supposed to have been. Because of the web’s structural similarities to crystal lattices, the degree of web deformation can be quantified with statistical crystallography techniques. Using an image data-analysis program, the NASA scientists analyzed the images of webs spun by spiders who were sober and intoxicated on various substances in terms of “numbers of cells and average areas, perimeters, and radii of cells.”
⁴

The results are fairly clear and, if they can be generalized in any way to human beings, are not very encouraging for caffeine aficionados. In a “Talk of the Town” feature, a
New Yorker
columnist says that although they may not realize it, “scientists at NASA labs…have identified the chemical agent responsible for human error,” by which he means caffeine:

It should be remembered that if a range of doses has not been studied, comparisons as between different drugs are virtually meaningless. And, of course, in comparing the effects of caffeine with those of other chemicals, both the
New Yorker
and NASA seem to be forgetting that caffeine acts as a natural chemical defense mechanism for plants against insects, a fact that may go a long way in explaining the perplexity of the poor spider.
⁶

Drawing of spider webs spun under the influence of various psychoactive drugs. The web spun by
Araneus diadematus,
the common house spider, is altered when the spider is exposed to chemicals. When juxtaposed with the drawing of a normal web, four drawings of spider webs spun by spiders exposed to marijuana, benzedrine, chloral hydrate, and caffeine demonstrate varying degrees of malformation. The results are obvious, even without the use of a sophisticated graphic analyzer. Compared with the webs spun normally or under the influence of marijuana, benzedrine, or chloral hydrate, the one spun after the administration of caffeine is clearly the most deformed. Each of the other webs exhibits an evident “hub and spokes” pattern, presumably the most fundamental aspect of the web paradigm. The caffeine web has lost any trace of this design and is almost completely disrupted.

Despite caffeine’s neurotoxic effects on some harmful insects, one species of beneficial bugs seem to enjoy the caffeine rush, at least if we are to believe the account of John Klapac, an East Coast beekeeper who feeds his little buzzers with the dregs from 55-gallon commercial containers of soft drink syrup. Klapac explains, “The bees love it—they get hyper from all the caffeine.” Evidently his bees don’t have access to enough nectar to last through the winter, and the sugary syrup, which they transform into a honeylike substance, is a perfect nutritional supplement. “Strawberry syrup makes a red product with strawberry flavor,” he adds, “and cola syrup produces an almost black substance with a cola-like taste.”

Coffee is a tropical glossy-leafed evergreen shrub or bush belonging to the genus
Coffea
of the Rubiacæe, or madder, family that is the source of several powerful pharmaceutical agents in addition to caffeine, including ipecac and quinine. Most of the twenty-five-odd species of the coffee plant grow wild in the tropics of the eastern hemisphere. The branches of every species bear small, creamy white flowers with a sweet fragrance like jasmine blossoms. Although
Coffea
is divided botanically into four groups, the coffee we drink comes from plants that all belong to one of these groups,
Eucoffea
. Some wild members of the other three groups are used by African natives as decorative vegetation and others as stimulants, but their fruit is generally inedible, and they have no currency in commerce.

Engraving from Dufour,
Traitez Nouveaux.
This engraving shows a branch from the coffee tree, a cylindrical instrument for roasting coffee, and a few roasted coffee beans themselves. (The Library Company of Philadelphia)

The earliest known and cultivated species is
Coffea arabica,
“the coffee shrub of Arabia,” indigenous to the Ethiopian massif. Now grown mostly in Latin America, it accounts for 75 percent of all coffee consumption worldwide. The other commercially important species,
Coffea canephora,
the main variety of which is
robusta,
supposed to have originated in Uganda and the Congo, is widely cultivated in Africa and Madagascar. Both species are also cultivated in Asia.

Comparison of the Methylxanthine Content of Arabica and Robusta Coffee Beans