I have just been reading the list of ingredients on a bottle of Pepsi. At the end of the list it says that it "contains a source of Phenylalanine" in bolder letters, as though it is a warning.

What is Phenylalanine, and why would the fact that Pepsi "contains a source" of it need to be written in bolder lettering?

Phenylalanine is the precursor to another amino acid called tyrosine. Phenylalanine is used by the brain to produce norepinephrine, a neurotransmitter depleted by stress, caffeine, nicotine, pollution, and some pharmacological and recreational drugs.

Its consumption releases beta phenylethylamine, a neuromodulator associated with mood enhancement and sexual stimulation.

Perhaps this is the reason that its inclusion was mentioned in bold.
Thnx for sharing this discovery of yours ,
Pin~Jinx / anarchist_who's found another reason to boycott Pepsi

Phenylalanine is an amino acid. The amino acids are the building blocks that make up proteins.

There is a disease called PKU (1 in every 10,000 newborns have this disease). People with this disease don't have the enzyme that lets their bodies process phenylalanine. The result is that it builds up in the bloodstream and causes a number of problems, including irreversible mental retardation and premature death. These effects will happen if the disease is not detected within the first few weeks after birth. People with this disease need to be put on low phenylalanine diets, which is quite a challenge because phenylalanine is found in most proteins.

As far as how this affects you ... if you're more than a few weeks old, don't already know you have the disease, and aren't mentally retarded, you don't have the disease and there's no reason for you to worry about it.

Thank you Pin~Jinx and methos5000 for explaining this so well to me. I'm pleased to know that it is safe to continue drinking my Pepsi!