Diet Pepsi is a no-calorie carbonated cola soft drink produced by PepsiCo, introduced in 1964 as a variant of Pepsi with no sugar. First test marketed in 1963 under the name Patio Diet Cola, it was re-branded as Diet Pepsi the following year, becoming the first diet cola to be distributed on a national scale in the United States.
In the 1960s and 1970s its competition consisted of Tab, produced by The Coca-Cola Company, and Diet Rite cola, produced by RC Cola. Diet Coke was introduced in 1982 and quickly became the primary competing diet cola to Diet Pepsi.
While the U.S. represents the largest single market for Diet Pepsi, it was launched in the U.K. in 1983 and has since become available on a global scale. The beverage composition, flavor variations and packaging varies based on the country of production. In some countries it is sold under the name Pepsi Light.
In the United States, Diet Pepsi is marketed as having zero calories, as FDA guidelines categorize products with fewer than five calories per serving to be labeled as containing “zero calories”.
Though it is represented worldwide as a low- or no-calorie beverage, the ingredients comprising its makeup vary in some cases by the country of origin. In the US, its ingredients are recorded as “carbonated water, caramel color, aspartame, phosphoric acid, potassium benzoate (preserves freshness), caffeine, citric acid, natural flavor; phenylketonurics: contains phenylalanine”. In Canada, the ingredient listing reads: “carbonated water, caramel color, phosphoric acid, aspartame (124 mg/355 ml, contains phenylalanine), sodium benzoate, caffeine, flavor, acesulfame potassium (32 mg/355ml), citric acid, dimethylpolysiloxane”. Comparatively in the UK, Diet Pepsi is listed as consisting of “carbonated water, colour (caramel E150d), flavorings (including caffeine), phosphoric acid, sweeteners (aspartame, acesulfame K), acidity regulator (sodium citrate), preservative (sodium benzoate), citric acid, contains a source of phenylalanine”.