Diet Coke artificial sweeteners 'under pressure' A Coca-Cola executive says the soda brand is 'under a bit of pressure' because of concern over its ingredients Overall sales of diet sodas are falling at a faster rate than regular sodas Diet Coke, the second-most popular soft drink in the country, may be losing some of its pop. During a conference call with analysts Tuesday, a Coca-Cola executive noted that the soda brand was 'under a bit of pressure' because of people's concerns over its ingredients, alluding to the growing wariness of artificial sweeteners in recent years. Steve Cahillane, who heads Coca-Cola's North American and Latin American business, noted that the issue wasn't specific to Diet Coke, but that many diet foods and drinks in the U.S. are facing the same concerns. Losing its appeal? Diet Coke, the second-most popular soft drink in the country, is 'under pressure' due to people's concerns over its 'unnatural' ingredients 'We believe very strongly in the future of Diet Coke,' Mr Cahillane nevertheless stressed, noting that the drink was still the number two soda in the U.S, after knocking Pepsi from that perch in 2010. The company still sells twice as much regular Coke as Diet Coke. Mr Cahillane also noted that the company is investing in boosting Diet Coke's performance, pointing to recent promotions with singer Taylor Swift as an example. Soda has been under fire from health advocates for several years now, and Americans have been cutting back on sugary fizz for some time. But in a somewhat newer development, diet sodas are falling at a faster rate than regular sodas, according to Beverage Digest, an industry tracker. Last year, for example, sales volume for Coke fell one per cent, while Diet Coke fell three per cent. Pepsi fell 3.4per cent, while Diet Pepsi fell 6.2per cent. Those figures aren't going unnoticed in Coca-Cola's Atlanta headquarters. This summer, the company launched its first ad addressing the safety of aspartame to ease concerns people might have. It has also distributed fact sheets on the topic to its bottlers and retailers who sell Coke products. Aware of the shift: Coca-Cola is now working on producing sodas made with natural, low-calorie sweeteners The Food and Drug Administration says aspartame may be safely used in foods as a sweetener, and the American Cancer Society has said that most studies using people have found that aspartame is not linked to an increased risk of cancer. Still, the broader trend in the U.S. has been toward foods and drinks people feel are natural or organic. And Coca-Cola is clearly aware of the shift; the company is working on producing sodas made with natural, low-calorie sweeteners. It also launched a version of its namesake drink sweetened with stevia in Argentina this summer. Stevia comes from a plant of the same name. Meanwhile, Coca-Cola said that sales volume for regular, full-calorie Coke rose two per cent in North America in its latest quarterly results reported on Tuesday. Coke Zero, which is made with artificial sweeteners and targeted more toward men, rose five percent. The company didn't break out Diet Coke's performance, but overall soda volume for the region was flat.