The University of Minnesota is among the few institutions in the world to be looking specifically at the effects caffeine has on children. In a lab at the university, 10 monkeys are currently recovering from their $37-a-week Kool-Aid habit that contained the caffeine equivalent of an 8- to 10-year-old drinking two cans of pop a day.
To approximate this, controlled amounts of caffeine were added to the tropical punch-flavored drink that was given to the monkeys, in addition to food and water.
When on caffeine, the monkeys "worked" hard for food -- measured by how often they pressed a lever that dispenses food pellets.
But when deprived of caffeine, they experienced withdrawal symptoms. Researchers know this because the monkeys' behavior changed markedly. Some became so listless they wouldn't even feed themselves -- they went from pressing a lever as many as 100 times per pellet of food to not at all.
"But if we hand-feed them, they will eat, which shows they are hungry," says researcher Marilyn E. Carroll, an associate professor of psychiatry in charge of the experiment. "What appears to have happened is that in withdrawal, they're experiencing a motivational deficit -- they've lost their motivation to work for food."
In particular, Ms. Carroll's study is designed to look at the effects of caffeine withdrawal on learning and performance in both young and old monkeys and then in human children.
Says Ms. Carroll: "It's surprising to realize that caffeine in childrenreally hasn't been studied a lot, especially when you consider that a 40-pound child gets four times the dose an average adult gets from a can of pop -- and children do drink a lot of pop. In pop machines and some fast-food places, it's hard to get a drink that isn't caffeinated, which is more evidence for the way our culture is sort of biasing our kids toward drinking caffeinated drinks."
Caffeine is a naturally occurring chemical compound found in more than 60 plant species.
While it may function in plants as a form of protection from predators, discouraging consumption by the bitter taste it imparts, people in all cultures have used it as a stimulant for thousands of years. Most preparations in health-food stores that claim to have energizing effects are related to caffeine.
"There aren't any other legal stimulants to the central nervous system. It is usually caffeine that is being sold, but perhaps in an unfamiliar form," says Dr. Verro Tyler, an expert in the use of natural herbs, who teaches at Purdue University's department of pharmacology.
Among the major sources of caffeine are:
* Seeds of Coffea arabic and related species, used to make coffee.
* Leaves of Thea sinensis, used for tea.
* Seeds of Theobromo cacoa, used to make cocoa and chocolate.
* Leaves of the South American plant Ilex paraguariensis, used to make a hot beverage called mate.
* Seeds of a South American plant in the genus Paullinia, which, when crushed, produce the beverage guarana.
* Kola nuts from the tree Cola acuminata, for the production of cola beverages.
Most adult Americans consume about 200 milligrams a day of caffeine through coffee, tea, soft drinks or over-the-counter medical preparations. Here are some common sources of caffeine and average caffeine content -- which can vary by brand and method of preparation -- from the U.S. Food and Drug Administration:
* Coffee, per 5-ounce cup: an average of 115 milligrams for coffee brewed by the drip method; 65 milligrams for instant coffee.
* Tea, per 5 ounce cup: an average of 40 milligrams for tea brewed from American brands; 60 milligrams from imported brands; 70 milligrams for a 12-ounce glass of iced tea.
* Cocoa, per 5 ounce cup: 4 milligrams.
* Chocolate milk, per 8 ounce cup: 5 milligrams.
* Milk chocolate, per 1 ounce: 6 milligrams.
* Dark chocolate, per 1 ounce: 20 milligrams.
* No-Doz: 100 milligrams.
* Cold-allergy remedies: Triaminicin, 30 milligrams; Dristan A-F TTC Decongestant, 16 milligrams.
* Pain relievers: Excedrin, 65 milligrams; Anacin Maximum Strength, 32 milligrams.
* Weight control: Dexatrim Extra Strength: 200 milligrams.