Not so sweet: Artificial sweetener aspartame linked to anxiety

TALLAHASSEE, Fla. — Aspartame is used as an ingredient in over 5,000 diet foods and beverages. Now, new research from Florida State University reports the artificial sweetener may be linked to a greater anxiety risk, an animal study concludes.

Mice exposed to aspartame exhibited anxious behavior. Notably, the anxious effects of aspartame on tested rodents extended up to two generations from the original males exposed to the sweetener.

“What this study is showing is we need to look back at the environmental factors, because what we see today is not only what’s happening today, but what happened two generations ago and maybe even longer,” says study co-author Pradeep Bhide, the Jim and Betty Ann Rodgers Eminent Scholar Chair of Developmental Neuroscience in the Department of Biomedical Sciences, in a university release.

This work was conducted, in part, thanks to previous research at the Bhide Lab focusing on the transgenerational effects of nicotine on mice. Those earlier projects indicated temporary, or epigenetic, changes in mice sperm cells. In contrast to genetic changes (mutations), epigenetic changes are reversible and don’t change the DNA sequence. Still, they can change how a body reads DNA sequences.

“We were working on the effects of nicotine on the same type of model,” Bhide adds. “The father smokes. What happened to the children?”

How aspartame affects the body

Aspartame was originally approved by the U.S. Food and Drug Administration (FDA) as a sweetener in 1981. Fast forward to today, and close to 5,000 metric tons of aspartame is produced annually. Upon ingestion, aspartame becomes aspartic acid, phenylalanine, and methanol. All three of those substances are known to have potent effects on the central nervous system.

Pradeep Bhide in his lab at Florida State University
Pradeep Bhide, the Jim and Betty Ann Rodgers Eminent Scholar Chair of Developmental Neuroscience in the Department of Biomedical Sciences. (Credit: Florida State University)

This latest research, led by doctoral candidate Sara Jones, entailed providing a group of mice drinking water containing aspartame. The water given to the rodents registered at approximately 15 percent of the FDA-approved maximum daily human intake. That dosage, which is roughly equivalent to six to eight 8-ounce cans of diet soda a day for a human, was provided to the mice for 12 weeks, but the greater study spanned four years.

Starting with directly exposed males, pronounced anxiety-like behaviors were observed in the mice through a variety of maze tests across multiple generations. “It was such a robust anxiety-like trait that I don’t think any of us were anticipating we would see,” Jones explains. “It was completely unexpected. Usually you see subtle changes.” 

When the mice were given diazepam (Valium), a benzodiazepine used to treat anxiety disorder in humans, rodents across all generations stopped acting so anxious.

Moving forward, the research team plans to publish more scientific work focusing on how aspartame may influence memory. Future studies will work to identify the molecular mechanisms facilitating the transmission of aspartame’s observed effect across generations.

The study is published in Proceedings of the National Academy of Sciences.