Consumers are wary of soda that contain aspartame as its artificial sweeteners. This fear of the effect of aspartame on their health was the main driver in changes in soda market share.

Latest figure from Beverage Digest, a trade publication, said that Pepsi has dislodged Diet Coke from the 2^nd top spot as Pepsi registered an 8.8 percent market share, while Diet Coke's share dipped to 8.5 percent, reports Adage.com.

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The figures are for 2014. Even if Pepsi regained the number two spot, Pepsi as well as Coke had lower volumes last year. Pepsi's volume dropped 1.8 percent, while Diet Coke's volume dipped 6.6 percent.

In effect, these developments meant that Pepsi regained the top 2 spot it held until 2010 when Diet Coke grabbed the second place in terms of volume.

Overall, Brand Coke which includes both the regular Coke and Diet Coke, still was the dominant brand with a 17.6 percent market share.

Besides the impact of consumer choice to shy away from products with aspartame, some analysts believe Pepsi' marketing approach may have influenced the shift. In particular, they point to the "Refresh Project" campaign of Pepsi that focused on community-building projects.

However, Pepsi recently reversed gears again and returned to star-studded advertisements and sponsorship of halftime shows in Super Bowl.

John Sicher, editor and publisher of Beverage Digest, says that in his opinion, aspartame is safe, but "there certainly is a subset of consumer who have had a withdrawal of enthusiasm about aspartame," which affects Diet Coke and other major diet soda brands.

Diet Pepsi reduced volume by 5.2 percent and Diet Dr. Pepper's volume dipped 7.9 percent. In contrast, the Fanta brand, a non-diet soda also owned by Coke, enjoyed a 5 percent boost in volume.

TagsCoke, Pepsi, soda drinks, aspartame