Diet Coke may not stay on the “must-have” lists of dieters for long, as shrinking sales continue to impact the soda giant.

Coca-Cola says sales of Diet Coke are still nose-diving as more and more people gravitate toward foods they feel are “fresh.”

Sandy Douglas, president of Coca-Cola North America, said the drink’s declining sales are due to consumers’ move away from diet and frozen products in recent years, with people reaching for options they consider to be fresh or natural.

“It’s a good dietary change, actually, for the country. But the impact on categories, and particularly categories that are appealing to diet-oriented positions, has been pretty negative,” he said.

During the second quarter, Coca-Cola said Wednesday that Diet Coke’s sales volume declined 7 percent. CEO Muhtar Kent said the drink’s challenge has been “very much a U.S.-centric one.”

Douglas said he thinks the trend toward products positioned as natural will endure. But he nevertheless expressed optimism for the future of Diet Coke, which is made with the artificial sweetener aspartame, as the company is starting to see its customer base “stabilize.”

Other beverage industry giants have blamed the decline in traditional diet sodas to concerns tied to the usage and safety of aspartame. These concerns convinced PepsiCo, Inc. it was time to replace the artificial sweetener with sucralose, another form of artificial sweetener.

While Coca-Cola doesn’t yet have plans to follow suit, Douglas said that PepsiCo’s decision could help raise awareness about the safety of diet sweeteners. He also noted that Diet Coke’s popularity has waned since its launch in the 1980s.