What’s the Difference Between Diet Soda and Zero-Sugar Soda?

If you’re a regular in the soda aisle at the grocery store, you may have noticed an uptick in zero-sugar sodas in recent years. From Coca-Cola to Pepsi, Dr. Pepper, and Mountain Dew, most of the classic soda brands have branched out to provide this seemingly healthier option.

Traditional diet versions, like Diet Coke, are still kicking around. But other soft drinks—like Diet Canada Dry, Diet Crush, and Diet A&W Cream Soda—have all been phased out and replaced in recent years by zero-sugar alternatives, which are reportedly not quite the same. 

These replacements aren’t surprising when you take recent soda sales into account. Even though it's been around since 2005, its manufacturer called Coke Zero “a bet for the future” due to its incredible growth in sales—5 percent in 2023, more than twice the growth of the brand’s portfolio in the same year. Other zero-sugar alternatives are becoming popular, too. So, what’s the story behind the drink’s massive success? Discover the origins of these soft drink types, plus key differences and more below.

1. The Origins of Diet Sodas
2. Artificial Sweeteners in Diet Sodas and Zero-Sugar Sodas
3. The Rise of Zero-Sugar Soda

The Origins of Diet Sodas

The first diet soda hit markets in 1952, and the industry has taken wild turns since. No-Cal, invented by Hyman Kirsch (a noted pioneer in the world of sugar-free soft drinks), replaced sugar with cyclamate, an artificial sweetener. The soda was initially intended for consumers with diabetes and cardiovascular issues. However, once No-Cal was on the shelves, it became clear that dieters were its primary demographic.

Diet-Rite Cola, which was released by the Royal Cola Company in 1958, was created to help people with diabetes and others who needed to limit their sugar intake. Instead of sugar, this soda was made with cyclamate and saccharin for added sweetness. By 1960, it was the fourth most popular soft drink, behind Coca-Cola, Pepsi, and 7-Up.

At this point, major soda brands felt that they needed to catch up and corner their own share of the market. This led to the creation of drinks like TaB by the Coca-Cola Company, which was the top diet soda in the 1960s and 1970s. In 1963, Pepsi released Patio (renamed Diet Pepsi a year later) to immediate popularity and celebrity endorsements (fans of Mad Men might even remember it). However, Diet Coke wasn’t released until 1982, largely due to concerns about associating the word diet with the iconic Coke trademark. (The drink became a smashing success.)

Artificial Sweeteners in Diet Sodas and Zero-Sugar Sodas

The sweetener used in most diet sodas today, including Diet Coke and Diet Pepsi, is aspartame, which was classified as “possibly carcinogenic” by the World Health Organization’s International Agency for Research on Cancer (IARC) in 2023. But that category is broad, including substances as varied as gasoline exhaust and aloe vera. In fact, experts say it’s unlikely that the amount of aspartame in diet sodas would cause any health problems, so long as drinks are consumed in moderation. Having a Diet Coke every day with lunch shouldn’t make you overly concerned about your aspartame intake (though daily consumption might lead to other health issues).

The soda industry has faced significant hurdles over the years, though, thanks to the artificial sweeteners used in diet formulas. The Delaney Clause of the 1958 Food Additives Amendment requires the FDA to ban all food additives that found to be carcinogenic. As scientific knowledge has evolved over time, some artificial sweeteners have been deemed carcinogenic, like cyclamate. This meant that various reformulations of classic diet sodas were necessary, especially as some consumers rejected the different flavor profiles of various alternative sweeteners. 

The Rise of Zero-Sugar Soda

Zero-sugar sodas really only began making waves in the 2000s. Compared to diet sodas, these soft drinks were heavily marketed to Millennials (and later, Gen Z) but weren’t advertised in quite the same way as sugar-free sodas were to Boomers or Gen X in previous decades. These drinks were positioned as ideal for consumers invested in their health who were seeking low-calorie, no-sugar alternatives to their favorite soft drinks.

The most significant differences between Coke Zero and Diet Coke are in the taste and ingredients. They both contain aspartame, but Coke Zero also uses the sweetener acesulfame potassium and has less caffeine. Comparatively, Diet Coke more closely resembles the original Coca-Cola formula. 

For consumers, the most obvious difference for Coke Zero might be right on the label—an aversion to the word diet. Taste of Home reports Greg Lyons, chief marketing officer of PepsiCo North America, has said, “No Gen Z wants to be on a diet these days. Younger people just don’t like the word diet.”

The word—which, for some, is off-putting—doesn’t seem to resonate with younger audiences, especially those who embrace more of a body-positive message. But in reality, there doesn’t tend to be much difference health-wise between traditional diet sodas and their zero-sugar counterparts.

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