I've been researching what's in my food lately, and it seems that most additives in foods are unsafe?

Artificial sweeteners and preservatives seem to be the biggest culprits. Some thickeners have bad side effects like guar gum, not in everyone it seems, but they're there none the less. I'm wondering how the FDA can approve of all of these additives? I know they do many studies to find if they are "safe" but I feel like there are so many angles and other variables to take into account that they don't, such as outside studies. I can't believe how much negative information is around the artificial sweetener aspartame (in nearly every diet beverage around) but it is still considered safe by the FDA.