Glycine
The single most abundant amino acid in collagen, making up around a third of its structure.
Substrate reasoning from biochemistry; no human trial has tested free amino acids for skin outcomes.
On the label: Glycine.
What it does for you
Supplies the raw material collagen is built from, so the building blocks are not the limiting step.
Why we use it
Included as substrate alongside the peptides that carry the signal. We are clear that this is a supporting role built on biochemistry rather than on skin trials.
Mechanism
Collagen is roughly one third glycine. The reasoning is that the body's own glycine production may not be generous enough for maximum collagen synthesis, making it worth supplying.