↵1-a The data on which this table is based are taken from the 1995 food balance sheets of the Food and Agriculture Organization of the United Nations (FAO), which allow a very rough estimate of average consumption of foodstuffs in a population. Individual consumption will of course depend on whether a person consumes a certain product at all and, if so, how much. Another uncertainty inherent in food balance sheets is that they do not correct for waste (e.g., losses in processing, coffee brewed but not drunk, etc.). One major advantage of food balance sheets is that data are available for all the countries of the world. Coffee: Caffeine content in coffee beans varies depending on the species. Arabicacoffees contain about 1.1% caffeine and Robustaabout 2.2% dry weight (Gilbert, 1984; Viani, 1993). The amount of caffeine extracted varies with preparation technique used, ranging from 75% in boiled coffee, 80% in espresso, and 85% in percolated coffee, to nearly 100% in filtered coffee (D’Amicis and Viani, 1993). Tastes differ in different countries, and the relative proportions ofRobusta and Arabica (and hence caffeine content) in the coffee blends vary. In Scandinavia, Arabica is used almost exclusively; in Southern Europe and North America, the proportion of Robusta can be 50 to 60% (D’Amicis and Viani, 1993). There is a tendency that preparation techniques with a greater caffeine extraction efficiency are used in countries that consume mainly Arabica coffee (e.g., filtered coffee in Sweden) and techniques with a lower extraction efficiency in countries where more Robusta is consumed (e.g., espresso coffee in Italy). For these calculations the caffeine content is taken as 1.6%, and the extraction efficiency is taken as 95%. Tea: The caffeine content in tea leaves depends on age of leaf (young leaves have about 4% by dry weight, old leaves contain less than half that), amount of fertilization (as fertilization increases caffeine content) season, and treatment after harvest (Graham, 1984b). About half the caffeine in tea leaves can be extracted, but the caffeine content in the beverage itself is strongly dependent on the brewing time (Graham, 1984b; IARC Working Group, 1991). For these calculations the caffeine content of tea is taken as 3% and the extraction efficiency as 50%.Maté: The caffeine content of maté ranges from 0.9 to 2.2% (dry weight) in a fresh leaf (Graham, 1984a). As usually prepared, 50 g of maté yields 1 liter of beverage containing a total of 160 mg of caffeine. The extraction figure used here is 0.3% of the total weight of the maté leaves. Cocoa: The caffeine content varies considerably in beans from different varieties of cacao trees: it is low in some (around 0.2% w/w in dry, defatted beans) but can be quite high in certain experimental clones (as much as 1%) (Shively and Tarka, 1984). For these calculations, the amount of caffeine consumed is assumed to correspond to 0.2% of the total domestic consumption of cocoa products.

↵1-b pers, persons.