These are all things, "diet", "sugar-free", "natural flavoring!"
Why? I'll answer that for you!
Most are 200 –400 times sweeter than sucrose. Brain is fooled in to thinking that an abnormally high amount of glucose has entered the bloodstream.
Pancreas actually secretes insulin in response. When the anticipated glucose is not delivered to the brain, hypoglycemia can result. The brain panics and sends out food craving messages.
Person then finds him/herself eating more foods (again, usually the wrong foods –high sugar/high fat). Any attempt at weight loss is sabotaged. „ Diet sodas therefore do not aid the weight loss effort.
Excess aspartic acid in free form (unbound to proteins) can accumulate in the brain by-passing the BBB. In excess becomes “excitotoxin” (can excite or over stimulate neurons to death).
Excess phenylalanine is dangerous in cases of phenylketonuria (PKU). Phenylalanine also competes with tryptophan for absorption in the brain. This can cause decreased levels of serotonin. (Contributing to depression).