The move comes amid a decline in sales, and as other companies are finding success with natural ways of sweetening sodas.
The new ads defend aspartame, citing scientific evidence that the artificial sweetener used in many diet sodas is safe.
Many nutrition experts agree.
"Many of the studies do in fact show aspartame is safe," says Dr. David Heber of the UCLA Center for Human Nutrition.
Studies done in animals decades ago suggested a cancer link, but even the American Cancer Society finds no credible evidence of that in humans.
The real problem with artificial sweeteners is that they're not likely to help people lose weight. Experts say diet sodas trick the body into thinking it's had something sweet.
"Your brain is activated but there are no calories there. So now you're hungry for that sugar. If you're now presented with a high fat high sweet treat, be it a brownie or a piece of cheesecake, you're gonna really gobble that down," Dr. Heber explains.
The ads come amid declining sales for all of the major soda makers.
On the flip side, consumers are turning to naturally sweetened Zevia, a zero-calorie soda that gets its sweetness from the stevia plant.
The company just reported record-breaking sales.
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