What are the side effects of diet sugar?

WildStar
I'm about to reduce my sugar usage in my coffe and other drinks and I want to to add ( Artificial Sweeteners / Sugar Substitutes ) or what is know by diet sugar , and I've heard that there is lots of side effects and I need to know if it's really dangerous or not ?
Updates
+1 y
I'm going to mix natural sugar with diet sugar to have the taste and reduce the amount of natural sugar I'm using because I've been using so much sugar lately because of coffe and latte , what do you think of that do any one of you have an idea about that ?
Updates
+1 y
can anyone tell me more about my last update , or what to do ?
What are the side effects of diet sugar?
8 Opinion