L-Phenylalanine isn't mentioned.

It's basically an amino-acid that the body uses to make the precursor to the brain chemicals that are supposed to regulate your mood, if you don't have enough good-mood building blocks through your diet you will have issues, this fixes that.

Can be a bit of a sneaking fix, for many it works very fast but for many it takes a bit of time, you just find less reasons to be in a bad mood and more reasons to be in a good mood over time, often without really noticing until you just one day realize that you simply deal with set-backs without it being a big deal and is motivated to do stuff every day, and realize that it isn't a new thing and that it has been the case for a while now.....

Bear in mind it's the L-Phenylalanine that is preferable as it's the natural amino, there is a B-phenylalanine available but the B version is synthetic..