https://pubmed.ncbi.nlm.nih.gov/28938797/ https://academic.oup.com/nutritionreviews/article/75/9/718/4101228

The existing animal studies and the limited human studies suggest that aspartame and its metabolites, whether consumed in quantities significantly higher than the recommended safe dosage or within recommended safe levels, may disrupt the oxidant/antioxidant balance, induce oxidative stress, and damage cell membrane integrity, potentially affecting a variety of cells and tissues and causing a deregulation of cellular function, ultimately leading to systemic inflammation.

There is controversy regarding how aspartame was passed as "safe" last century - essentially lobbying.

The lobbying pressure pro-aspartame is significant, due to the enormous sums - profit - involved.

CONCLUSION

Current scientific knowledge about the safety of aspartame, as reviewed here, is based mostly on animal studies. These studies suggest that aspartame, even at recommended safe dosages, might not be safe. Several of these studies (in vitro as well as in vivo) that investigated both higher and safe dosages indicate that aspartame or its metabolites cause an oxidant/antioxidant imbalance, induce oxidative stress, and damage membrane integrity (lipid, protein, and nucleic acid), possibly affecting most cells and tissues. Aspartame is directly involved in the development of oxidative stress, which is a hallmark of systemic inflammation (Figure 3). Several animal studies have also reported a deleterious effect of aspartame exposure on body weight, adiposity, and/or glucose tolerance and insulin levels. These are summarized in a 2016 review by Fowler.125 Thus, there is a need for additional detailed human studies and comprehensive characterizations of the physiological processes affected by aspartame. This is of particular importance, as diabetic and other individuals with gut dysbiosis may already be at increased risk of systemic inflammation because of the inflammatory nature of their conditions. Data reviewed in this paper suggest that aspartame use could not only exacerbate existing systemic inflammation but also cause inflammation if healthy individuals ingest it on a regular basis.

This is not even looking at the other issues with aspartame, including possible weight gain, exacerabtion of mental health issues:

According to some studies, aspartame and other artificial sweeteners can lead to weight gain instead of weight loss 12. Aspartame has been linked to increased appetite, diabetes, metabolic derangement and obesity-related diseases 2.

One study showed that aspartame causes greater weight gain than a diet with the same calorie intake but no aspartame 1. Another study found that even acceptable daily intakes of aspartame might make you hungrier and lead to weight gain 3.

. However, some research suggests an association between aspartame intake and metabolic damage to the central nervous system (CNS), such as changes in enzyme and neurotransmitter activities 2. Aspartame acts as a chemical stressor by elevating plasma cortisol levels and causing the production of excess free radicals. High cortisol levels and excess free radicals may increase the brain’s vulnerability to oxidative stress which may have adverse effects on neurobehavioral health 3.

There is also some evidence that high-aspartame consumption may lead to weaker spatial orientation, irritability, depression, and other neurobehavioral conditions 14. However, these studies are limited in scope and further research is needed to determine the long-term effects of aspartame on human health.