Aspartame, a commonly used sweetener in zero-sugar products such as diet soda, could have a negative impact on learning and memory, which may be transmitted to offspring, according to a new study. Researchers at Florida State University found that mice consuming aspartame well within the levels officially deemed safe showed signs of cognitive impairment.

In July, the World Health Organization (WHO) said aspartame was safe to consume despite some evidence linking it to a common type of liver cancer. However, some questioned the classification due to lack of strong evidence. The WHO’s recent review, however, didn’t look at the potential effects of aspartame on learning and memory abilities.

Pradeep Bhide, a researcher at the Department of Biomedical Sciences at Florida State University, and his team gave male mice doses of aspartame equivalent to 7% to 15% of the maximum daily consumption advised by the Food and Drug Administration (FDA). They then put the mice through tests to assess their memory and learning skills.

Aspartame is one of six non-nutritive sweeteners approved by the FDA. The others are advantame, neotame, sucralose, saccharin and potassium. The FDA set the acceptable daily use of aspartame at 50 milligrams per kilogram of body weight and has said the six sweeteners are safe if they are used in moderation, with some specific exceptions.

In the study, the mice had to learn to find a “safe” escape box out of 40 choices in a circular space. While the aspartame-free control group found the box quickly, the mice who had been given the sweetener took much longer to complete the task.  The exposed males who bred with females not exposed to aspartame had offspring with similar deficiencies.

Previous studies have shown that aspartame consumption is associated with neurobehavioral changes including anxiety-like behavior, learning and memory deficits. However, it wasn’t known if cognitive deficits such as learning and memory deficits linked with aspartame were heritable — this new study has addressed this question.

“The spatial working memory deficit is apparent by four weeks of aspartame consumption, and persists until 12 weeks at least, the longest duration examined,” the researchers wrote in their study, in the journal Scientific Reports. “The cognitive deficits are transmitted to male and female descendants along the paternal lineage.”

Growing risks

Aspartame is a non-nutritive sweetener, meaning it has no carbohydrates and doesn’t provide the body with energy or calories as sugar does. However, unlike other sweeteners that are excreted from the body unchanged, aspartame is metabolized. Its use is approved in common household sweeteners, carbonated drinks and other food products.

This popular sweetener is broken down in the gastrointestinal tract into phenylalanine, aspartic acid, and methanol, the researchers explained. Phenylalanine crosses the blood-brain barrier and it’s a precursor of neurotransmitters dopamine, epinephrine, and serotonin. These regulate memory, mood, motivation, and motor function.

However, aspartame’s risks go way beyond cognitive skills. Studies have linked its consumption to depression, heart disease, dementia, diabetes, cancer and migraines. Researchers are now also exploring whether artificial sweeteners, including aspartame, can increase feelings of hunger, leading to a higher calorie intake and weight gain.

“Aspartame’s adverse behavioral effects may be more pervasive than currently realized, and aspartame’s safety evaluations should consider potential effects in the directly exposed individuals as well as their descendants,” the researchers wrote.