DelanceyPlace.com-“Today’s selection– from The Most Delicious Poison by Noah Whiteman. The surprising—and dangerous—properties of caffeine”:
“Caffeine and the human mind seem like a match made in heaven. But even though billions of people imbibe caffeinated beverages each day, caffeine first evolved in the absence of humans. The two main species cultivated for coffee beans, Coffea arabica (the source of arabica beans) and C. canephora (the source of robusta beans), are both native to the highlands of Ethiopia but are now grown all over the world in similar climates.
“As a PhD student, I used to buy coffee beans from a St. Louis roaster called Kaldi’s Coffee. It was there that I learned about Kaldi, the apocryphal ancient goat herder mentioned in a 1671 treatise on coffee by the Maronite chronicler and professor Antoine Faustus Nairon. He wrote of a ‘certain camel herder or, as others say, of goats’ from ‘Arabia Felix,’ who had complained to the monks that he had been awoken at night by his goats, which seemed to be ‘jumping.’
“Nairon explained that the prior of the monastery decided to find out why. When he investigated, he found the goats eating the berries of the coffee plant. A potion he made from the boiled beans gave him insomnia, and so he then ordered the rest of the monks to drink it to help them stay awake during the night watch and evening prayers.
“We don’t know for sure when coffee was first cultivated by humans. However, it was widely used in the Arabian Peninsula in antiquity, coming to Yemen through the Yemenite Sufi community around the fourteenth century BCE. But coffee didn’t make it to Europe until the early 1600s. The Dutch began cultivating it in glasshouses in Amsterdam by 1616 and then in plantations in the East Indies. Thereafter came cultivation by the French, Spanish, and British in their own colonies.
“The root of the word coffee is traced to the Arabic qahwah, which may have originally referred to a kind of wine but has the root qahiya, which means ‘to have no appetite.’ So the dark, red-wine-like color of coffee coupled with its appetite-suppressing effect are embodied in its name.
“We didn’t breed plants to produce caffeine, although we’ve helped create different modern cultivars from their wild relatives through artificial selection. These and all other caffeine-producing plants were making caffeine tens of millions of years before any humans were walking the earth.
“On October 7, 1984, a breakthrough was announced in the New York Times” ‘Caffeine Is Natural Insecticide, Scientist Says.’ As the headline suggests, biologistJames Nathanson had just demonstrated that caffeine is indeed a potent natural insecticide. Nathanson discovered this by incorporating powdered tea leaves and coffee beans into artificial caterpillar food, which he then gave to newly hatched tobacco hornworm caterpillars, which don’t feed on plants containing caffeine in the wild. The hornworm adult is also called a hawk moth.
“What Nathanson found shocked the world (although, by now, probably not you): ‘At concentrations from 0.3 to 10 percent (by weight) for coffee and from 0.1 to 3 percent for tea, there was a dose-dependent inhibition of feeding associated with hyperactivity, tremors, and stunted growth. At concentrations greater than 10 percent for coffee or 3 percent for tea larvae were killed within 24 hours.’
“Further experimentation revealed that the level of caffeine naturally found in undried tea leaves (0.68 to 2.1 percent) or undried coffee beans (0.8 to 1.8 percent) was sufficient to kill all of the caterpillars. Nathanson found the same insecticidal effects of caffeine on mosquitoes, beetles, butterflies, and true bugs, including at concentrations found in nature.
“His most telling experiments involved spraying a mixture of caffeine on tomato leaves, the typical host plant for hornworms. Tomatoes don’t produce caffeine, so these experiments were designed to mimic what the sudden evolution of caffeine might do to an herbivore that found itself eating a caffeine-producing plant. As the concentration of caffeine went up, there was a concomitant reduction in the amount of leaf chewed by the caterpillars. In other words, the caffeine protected the plant from attack by the hornworms.
“A similar effect was found in 2002, when scientists in Hawaii accidentally discovered that a caffeine solution being tested as a toxicant to control the coqui, an invasive frog introduced from the Caribbean, also killed most of the large slugs found in their field plots. The researchers followed up by spraying or dipping vegetables in solutions containing caffeine concentrations of 1 to 2 percent, the same levels found in coffee beans, and offering them to the mollusks. Most of the snails and slugs died. And at far lower concentrations (0.01 percent), caffeine deterred them from feeding.
“Although caffeine mimics the insecticidal effects of coffee or tea when sprayed artificially on plants that don’t make it, this surface application is quite artificial. After all, the caffeine is made naturally inside coffee and tea plants’ cells. Another way to sort it out would be to endow a plant species that does not normally synthesize caffeine in its cells with the ability to make it and see how resistant its leaves become.
“Biologists did just that by genetically engineering caffeine production in tobacco plants, which don’t normally make caffeine. The researchers spliced three caffeine-producing genes from the coffee plant genome into the tobacco plant’s genome in the laboratory.
“These transgenic tobacco plants produced levels of caffeine similar to those found in coffee plants. Leaves from tobacco plants carrying coffee plant caffeine genes and control leaves without these genes were fed to tobacco cutworm caterpillars. The leaves producing caffeine were 99.98 percent less susceptible to herbivory than were the control leaves.
“In naturally occurring caffeine-bearing plants like citrus, coffee, and tea, genes encoding the enzymes used to make caffeine evolved from existing genes that had performed a different function. Although we cannot board a time machine to determine why caffeine first evolved in any plant, the only known function of caffeine in plants is as direct or indirect defense against natural enemies. This role seems obvious, thanks to Nathanson’s experiments. But caffeine might have first evolved as a molecule the plant used to signal the presence of stressors, just as salicylic acid serves as a hormone that signals the presence of attackers, rather than as a defensive strategy. Under this model, only later did caffeine become co-opted by plants as a toxin, just as willows took the ubiquitous plant-signaling hormone salicylic acid and turned it into a toxin by making much more of it.
“Not surprisingly, some specialist herbivores of coffee plants have evolved the capacity to resist the toxic effects of caffeine. The most troublesome is the coffee berry borer, a small beetle that tunnels into the fruit and lays eggs in the beans. The larvae of this beetle consume the bean from within, rendering it unusable for coffee bean production. The beetle is native to the same African regions that gave rise to the two Coffea species now cultivated in the worldwide tropics.
“The coffee berry borer has found coffee plants wherever they are, even in Hawaii, costing producers at least $500 million per year in damaged plants globally. Coffee is second only to petroleum in value as a global commodity, valued at $83 billion per year, and the borer is a major threat. The beetle itself cannot tolerate the insecticidal caffeine in its food. To get around it, the insect relies on enzymes produced by the bacteria living in its gut—its microbiome—which detoxify the caffeine.
“When these beetles were treated with antibiotics that killed the bacteria and given their normal diet of coffee beans, they perished just as any other insect fed this diet would. The amount of caffeine consumed by one of these beetles in a meal is equivalent to the amount you’d find in five hundred cups of coffee, ten times the level that killed twenty-one-year-old Lachlan Foote in the early morning hours on New Year’s Day in 2018.
“Foote’s tragic death in Australia was caused by an accidental caffeine overdose. He’d added one teaspoon of pure caffeine powder to a protein shake. After saying good night to his parents, he was found by his father in the bathroom, where he had died. It is not clear where he obtained the caffeine, but there was no warning label found on the bag he had used to store it.
“Foote consumed at least five thousand milligrams of caffeine, equivalent to fifty cups of coffee. The FDA’s recommended daily allowance for adults is four hundred milligrams. In the wake of his death, the family successfully pushed the Australian government to ban food additives with caffeine concentrations above 5 percent and liquids with levels above 1 percent. A ban went into effect less than a year later.”