Aspartame, a common sweetener used in Diet sodas, will be declared a carcinogen by the World Health Organization in mid-July.

The International Institute for Research on Cancer (IARC), a branch of the WHO, will release a new review of aspartame. The agency will classify the sweetener as “possibly carcinogenic to humans,” according to Reuters.

A separate WHO committee that evaluates the safety of food products will release guidelines on how much aspartame is safe to consume.

In a statement to Forbes, American Beverage, which represents Coca-Cola Co. and PepsiCo, maintained that aspartame is safe. It stated that multiple food safety agencies, including the FDA, “continue to find aspartame safe,” and they dismissed IARC as “not a food safety agency.”

-A history of conflicting guidance on aspartame-

In March 1973, American pharmaceutical company G.D. Searle attempted to get aspartame approved by the US Food and Drug Administration (FDA), but the request was denied. Scientists found that the product could cause neurological disorders, and some accused Searle of withholding or falsifying safety testing.

Searle spent millions of dollars on over 100 additional studies on aspartame, including animal testing. At the same time, experts filed objections due to toxicity concerns.

Because of the studies that Searle conducted, aspartame was approved for use in dry foods in July 1974 — despite reports from an independent FDA board that the drug may induce brain tumors.

The Ramazzini Institute, an Italian nonprofit that conducts scientific research to prevent cancer, began studying the effects of aspartame on rats in 1997.

The Ramazzini Institute reported in 2006 and 2007 that aspartame could cause increases in malignant tumors.

Scientists warned of brain lesions, cancer, and reduced learning and memory capabilities since 1977.

A 1997 paper in Headache Journal reported that young women who chewed sugarless gum containing aspartame experienced migraines, and a 2008 study in the European Journal of Clinical Nutrition stated that aspartame could lead to mental disorders, including issues with learning and retaining knowledge and worsened emotional functioning.

Dozens of studies have linked the consumption of aspartame to cancer, cardiovascular disease, Alzheimer’s disease, seizures, strokes, and dementia. They have also found that consumption can result in abrupt changes in mood, headaches, and migraines.

In addition, a 2022 study found that aspartame is linked to anxiety in mice, and the effect remained for as many as two generations.