In the face of declining sales of both full-calorie and diet soft drinks—many of which are made with the low-calorie sweetener aspartame—Coca-Cola took the offensive with a line of ads defending sweeteners.

Sales of soft drinks in the US have fallen across the board in the past year, but declines have been particularly pronounced in the diet category. Volume sales for Coke fell 1 percent compared to 3 percent for Diet Coke; Pepsi sales fell 3.4 percent compared to 6.2 percent for Diet Pepsi.

Coke’s campaign is an attempt to refocus a national conversation around soft drinks that has turned increasingly to their role in fueling climbing obesity rates. An initial phase in January 2013 outlined the company’s efforts to fight obesity while pointing to its many diet drink options in a video commercial titled “Coming Together.”

The new print ads appeared in USA Today in the Atlanta area, the Atlanta Journal-Constitution and the Chicago Tribune. Under the headline, “Quality Products You Can Always Feel Good About,” they tout third-party studies on the safety of low- and no-calorie sweeteners.

Despite FDA’s assertion aspartame is safe for use in foods as a sweetener and the American Cancer Society’s admission most studies have failed to link aspartame consumption to increased risk of cancer, the public remains wary. Declining sales of diet sodas suggest Americans are worried about more than obesity when making their choice in the soft drink aisle.

“Even if [aspartame is] 100 percent safe to use, it’s still problematic from a nutrition standpoint,” Andy Bellatti, a registered dietician, told the Christian Science Monitor. Bellati notes ingredients such as aspartame simply keep individuals sucking down the sweets instead of reaching for a more wholesome option.

Karen Congro, a nutritionist and director of the Wellness for Life Club at the Brooklyn Hospital Center, questions the research. “Despite claims from Coke and other companies about the safety of aspartame, we still don’t know its long-term effects,” Congro told USA Today. “Relying on artificial sweeteners probably causes cravings for sweets and sugar, which can contribute to obesity and poor eating habits.”

Recognizing the various concerns over artificial sweeteners, Coke and Pepsi are both working on new products featuring low-calorie, natural sweeteners. Around the end of June, Coke launched a 64-calorie, stevia-sweetened product called “Coca-Cola Life” in Argentina. Analysts say the product is well-equipped to compete in Argentina’s burgeoning health and wellness market, and could steal market share from vitamin- or antioxidant-enriched flavored waters.

Will Coke’s campaign pay off? Watch trends in diet soda sales going forward to find out.

Click here to download a PDF of Coke's print ad