Diet Pepsi, also known as Pepsi Light in some regions, is a sugar-free alternative to regular Pepsi. For many years, it relied on aspartame as its primary artificial sweetener. However, responding to consumer concerns and evolving preferences, PepsiCo has made significant changes to the formulation of Diet Pepsi, including the introduction of an aspartame-free version. This article explores the history, ingredients, health considerations, and market positioning of Diet Pepsi, with a particular focus on the aspartame-free option.
A Brief History of Diet Pepsi
Diet Pepsi was first test-marketed in 1963 under the name Patio Diet Cola. The following year, it was rebranded as Diet Pepsi and launched nationally, becoming the first diet cola to be distributed on a national scale in the United States. The drink's distribution later expanded overseas. Diet Pepsi competed primarily with The Coca-Cola Company's Tab in the 1960s and 1970s; however, The Coca-Cola Company introduced Diet Coke in 1982, which has since been the principal competing product to Diet Pepsi.
The Role of Aspartame
Aspartame, an artificial sweetener, has been a subject of debate and research for decades. The Food and Drug Administration (FDA) has regulated the use of aspartame since 1974 and approved it as a general-purpose sweetener in 1996. The acceptable daily intake for aspartame established by the FDA is 50 milligrams (mg) per kilogram (kg) of body weight per day. A 12-ounce can of diet soda contains about 200 mg of aspartame, so based on these guidelines, a person weighing about 150 pounds (or 68 kg) could drink around 17 cans of diet soda per day.
However, aspartame is not safe for people with phenylketonuria (PKU), a hereditary disorder that causes phenylalanine to build up in the body. Therefore, people with PKU must strictly limit their phenylalanine intake and should always choose diet drinks without aspartame.
Health Concerns and Controversies Surrounding Aspartame
Researchers and consumers have also worried about a possible link between aspartame and cancer for decades. In July 2023, the World Health Organization (WHO) reclassified aspartame as “possibly carcinogenic to humans” based on limited evidence. Even so, the WHO still advises that 40 mg/kg of body weight is a safe amount of aspartame to consume per day. The FDA disagrees that the limited evidence points to human cancer risk, citing research that found no link between low- and no-calorie sweeteners and beverages and increased cancer risk in humans.
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More recent studies are mixed in their conclusions, too. A data-mining analysis published in 2025 determined that artificial sweeteners, including aspartame, might potentially increase the incidence of kidney cancer, low-grade glioma, breast cancer, and prostate cancer. The study’s researchers “strongly advise the public to reduce their intake of artificial sweeteners to alleviate common health issues such as cardiovascular disease, diabetes, and irritable bowel syndrome.” Yet another study published in 2025 found no association between aspartame consumption and invasive breast cancer risk.
Along with the study of aspartame’s potential cancer risks, more research is needed on other potential health concerns of the sugar substitute. In a review of 29 studies, researchers linked aspartame with neurotoxic effects, such as behavioral concerns, mood disorders, and memory and learning impairments. (It’s important to note that some of the studies occurred in humans, while others took place in animals, so it isn’t entirely clear how those effects would translate to humans.) Older research also associated aspartame with behavioral and cognitive problems - such as headaches, irritable mood, depression, and insomnia.
The Shift to Aspartame-Free Diet Pepsi
Big changes were coming to Diet Pepsi. In response to consumer demand, PepsiCo announced that Diet Pepsi would no longer be made with the artificial sweetener aspartame. According to Seth Kaufman, SVP Pepsi and Flavors Portfolio, PepsiCo North America Beverages, consumers wanted aspartame-free Diet Pepsi, and PepsiCo was delivering. The company recognized that consumer demand was evolving and expressed confidence that cola-lovers would enjoy the crisp, refreshing taste of this new product.
The New Sweetener Blend
PepsiCo replaced aspartame with a different artificial sweetener-a blend of sucralose and acesulfame potassium. This combination provides consumers with the crisp, refreshing zero-calorie cola taste they expect. In other words, PepsiCo is using a sweetener similar to Splenda, which is closer to sugar in origins than aspartame.
This is a radical move for PepsiCo, as it positions Diet Pepsi as an entirely different option compared to other diet colas (most notably Diet Coke). Consumers making a choice between Diet Coke or Diet Pepsi are now making a choice between aspartame or sucralose, giving that choice a much more significant meaning.
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While some consumers have voiced concerns about the safety of sucralose, on the whole, science has given sucralose the green light of consumer safety.
Variations of Diet Pepsi
Additional variations of Diet Pepsi/Pepsi Light have been introduced over the years since the drink's debut, wherein other flavors (such as wild cherry, vanilla, lemon, and lime) have been added to the cola. There is also a variant that has no caffeine: Caffeine-Free Diet Pepsi was the first Diet Pepsi variant and introduced by PepsiCo in 1982. Diet Pepsi Wild Cherry was launched in 1988. Both are still produced today. Though Diet Pepsi is represented worldwide as a low- or no-calorie beverage, the ingredients comprising its makeup vary in some cases by the country of origin.
Packaging and Advertising
When it was first introduced in 1964, Diet Pepsi was packaged in glass bottles and was also made available in can format. The logo used in the packaging and advertisement of Diet Pepsi has changed multiple times since its original iteration. In October 2008, PepsiCo announced it would be redesigning its logo and re-branding many of its products, including Diet Pepsi. The brand's blue and red Pepsi Globe logo became a series of "smiles," with the central white band arcing at different angles depending on the product. The Classic Sweetener Blend variety was distinguished by its use of the 2003-2006 wordmark along with the "smile" logo and a light blue label background in contrast to the modern formulation's silver label. By mid-2017, packages of Classic Sweetener Blend dropped the 2003 wordmark and began using the modernized wordmark instead.
While it was initially advertised alongside Pepsi, Diet Pepsi began to be promoted independently in the late 1960s. The first television advertisement to feature Diet Pepsi as a standalone product was "Girlwatchers," which placed focus on the cosmetic aspects of the beverage. The musical jingle from this ad generated popular culture appeal to the extent that it was eventually recorded and played on the radio, and later became a Top 40 hit.
Since its inception, musicians, professional athletes, actors and actresses have been featured prominently in the promotion of Diet Pepsi. In 1985, immediately following Super Bowl XIX, the game's respective quarterbacks, Joe Montana (of the San Francisco 49ers) and Dan Marino (of the Miami Dolphins), met in a hallway of what appeared to be a football stadium. In the late 1980s, Michael J. Fox appeared in commercials for Diet Pepsi, including a memorable commercial that featured him making a robot clone of himself. During the early 1990s, R&B singer Ray Charles was featured in a series of Diet Pepsi ads featuring the brand's then-current tagline, "You got the right one, baby!" Supermodel Cindy Crawford became a recurring celebrity endorser for the Diet Pepsi brand at this time as well, beginning with a 1991 television ad in which she purchases a can of the drink from a vending machine on a hot summer day.
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Diet Pepsi vs. Pepsi Zero Sugar
Both Diet Pepsi and Pepsi Zero Sugar contain carbonated water, caramel color, aspartame, phosphoric acid, potassium benzoate, caffeine, and citric acid. The ingredients aren’t listed in exactly the same order. For example, aspartame is the third ingredient in Diet Pepsi and the fourth in Pepsi Zero. Diet Pepsi also lists the sweetener acesulfame potassium, which is not in Pepsi Zero.
Diet Pepsi has a silver can, and Pepsi Zero has a black can, which is useful to know if you’re trying to find them on your grocer’s shelves. Both have the round red, white, and blue Pepsi logo.