PepsiCo said Friday it was bowing to customer demand and doing away with the controversial sweetener aspartame in its diet line of cola drinks in the US. Starting in August, Diet Pepsi, Caffeine Free Diet Pepsi and Wild Cherry Diet Pepsi will be sweetened with a mixture of sucralose and acesulfame potassium, the company said. The blend replaces aspartame, an artificial sweetener approved by the US Food and Drug Administration but which has been plagued by criticism for years that it poses health risks.