Caffeine occurs naturally in the seeds, leaves, or fruits of more than sixty-three plant species throughout the world. The primary sources available in the United States, however, are coffee, tea, cacao (cocoa), and kola (cola) plants. These are grown and produced in tropical locations and shipped all over the world. Two other plants, maté and guarana, are primarily grown and consumed in South America as yerba maté and guarana bars and drinks (soda drinks or brewed hot drinks).

Table 9.1 lists the four major sources of caffeine, the parts of the plants that are consumed, and the locations in which the plants are grown. Of the three species of coffee, coffea arabica L. accounts for about three-quarters of all coffee consumption. Spices and other substances, such as vanilla and chocolate, can be added to make flavored coffees.

The three major tea types (green, oolong, and black) all come from the same species of plant; differences in flavor and color are a result of how the tea leaves are processed. For green tea, the leaves are steamed and dried. For oolong tea, the steamed leaves are partly fermented before they are dried. And for black tea, the steamed leaves are completely fermented before they are dried. As with coffee, spices and other flavorings can also be added to vary the taste of tea.

There are many products on the market today that are called "teas" even though they do not contain tea leaves. Virtually any beverage prepared by steeping substances in hot or boiling water is popularly called a tea. Herbal teas do not contain tea leaves or caffeine.

Not all plants contain equal concentrations of caffeine. Different methods of processing and brewing can also affect the amount of caffeine per cup or glass of a beverage. When calculating the amount of caffeine per cup or glass, a person must keep in mind the size of the cup or glass, and whether he or she dilutes coffee or tea with another substance, such as milk.

Of caffeinated drinks, coffee contains the highest concentration of caffeine. (See Table 9.2.) The way it is prepared, however, can change the amount of caffeine it contains. In general, coffee made in a drip-style coffee maker is highest in caffeine content. A six-ounce cup of coffee made by the drip method contains between 110-150 milligrams (mg) of caffeine; percolated coffee contains 64-124 mg of caffeine; and instant coffee contains 40-108 mg. Tea has significantly less caffeine than coffee, but the longer it is allowed to steep, the higher the caffeine concentration. A one-minute brew for a six-ounce cup of tea contains between thirty-five and forty-six mg of caffeine; a three-minute brew contains twenty to forty-six mg of caffeine. A hot cocoa mix typically contains six mg of caffeine. Both cocoa and cola drinks generally have lower levels of caffeine ounce per ounce than tea and coffee. However, cocoa contains large amounts of theobromine, a chemical related to caffeine that has the same stimulating effect.

Consumers should be aware that many popular over-the-counter (OTC, or nonprescription) medications contain caffeine. Caffeine is used in some OTC and prescription pain relievers because some studies have shown that caffeine increases their effectiveness. Caffeine is also a major ingredient in most preparations to help individuals stay awake and in OTC weight-control products.

TABLE 9.1
Where caffeine comes from
SOURCE: Created by Information Plus Staff for Thomson Gale from various data sources

TABLE 9.2
Comparison of caffeine amounts in beverages and other sources
SOURCE: Created by Information Plus Staff for Thomson Gale from various data sources