Studies on the safety of the natural sugar substitute stevia are somewhat conflicting. Of three of the latest studies, two confirmed at least some damage within the hippocampus of the brain (a major memory area), while one found no problems. In fact, the last study showed that stevia enhanced brain repair.

A study out of Egypt found mild alterations in some cells in the hippocampus and some minor inflammatory changes.

A study conducted in 2016 using mice exposed to stevia found that compared to aspartame and sucralose, stevia caused the greatest damage to the animals’ hippocampi. The authors of that paper noted that stevia extract contains high levels of iron, manganese, and cobalt, all of which are neurotoxic metals.

The third study out of Armenia and completed in 2017 found no damage to the brain, and in fact found protection by its ability to stimulate special protective molecules in the brain. In this study, stevia stabilized neuron membranes and acted as a powerful antioxidant, both good things.

Other studies found stevia to be glucose-reducing, anti-inflammatory, antihypertensive, as well as reducing insulin resistance, and having immunity-modulating effects. Human studies have found no harmful effects, but these studies are somewhat limited.

Overall, I would say stevia is probably safe as long as it is not used in excess. But as far as I’m concerned, monk fruit is the best natural sweetener.