NEW YORK – For the last several years, sales of zero- and reduced-calorie soft drinks had been the bright spot in soft drink sales — but that wasn’t the case for the 52 weeks ending Nov. 23, the Wall Street Journal reports.

Big name companies like Coca-Cola and PepsiCo banked on zero-calorie sodas to spur sales of soft drinks when American consumers started drinking fewer regular carbonated beverages in the latter years of the 20th century. With more concern over obesity, the strategy worked, with diet soda consumption jumping from 26% to 31% between 1990 and 2010, according to Beverage Marketing Corp.

Recently, the healthful aura of diet soft drinks has been tarnished, with store sales of no- and reduced-calorie soda dropping 6.8% in dollar terms for the 52 weeks ending Nov. 23. Sales of regular soft drinks declined 2.2% during the same time period, according to Nielsen scan data. “We are seeing a fundamental shift in consumer habits and behaviors,” said Indra Nooyi, chairman of PepsiCo.

A Mintel survey in March found that soda has lost its appeal to Millennials, while health concerns over artificial sweeteners found in diet soda, such as acesulfame potassium, aspartame and sucralose have risen. To counter such claims, soft drink companies have launched marketing initiatives defending the sweeteners, such as Coke’s summer print ad campaign that touted more than 200 studies providing aspartame’s safety. Coke and PepsiCo have been studying alternative sweeteners.