Coca-Cola and Pepsi decided to change the recipes for their drinks to avoid putting a cancer warning label on the bottle, to comply with California laws.
The new recipe for caramel coloring in the drinks has less 4-methylimidazole – a chemical which California has added to its list of carcinogens.
The change to the recipe has already been introduced in California.
Coca-Cola and PepsiCo say rolling out the new recipe across the US makes the drinks more efficient to manufacture.
“While we believe that there is no public health risk that justifies any such change, we did ask our caramel suppliers to take this step so that our products would not be subject to the requirement of a scientifically unfounded warning,” Coca-Cola representative Diana Garza-Ciarlante told the AP.
The chemical has been linked to cancer in mice and rats, according to one study, but there is no evidence that it poses a health risk to humans, said the American Beverage Association, which represents the wider industry.
The US Food and Drug Administration claims a person would need to drink more than 1,000 cans of Coke or Pepsi a day to take in the same dose of the chemical that was given to the animals in the lab test.
Coca-Cola and PepsiCo account for nearly 90% of the fizzy drink market, according to industry tracker Beverage Digest.