Complex sentence: The safety of aspartame has been studied extensively since its discovery with research that includes animal studies, clinical and epidemiological research, and postmarketing surveillance, with aspartame being one of the most rigorously tested food ingredients to date.
Split into simpler sentences: The safety of aspartame has been studied extensively since its discovery with research that includes animal studies, clinical and epidemiological research, and postmarketing surveillance. Aspartame is one of the most rigorously tested food ingredients to date.