The tripeptide has a donor-atom arrangement that binds copper(II) with high affinity under physiological conditions, and once that was appreciated it became clear that most of the reported activity tracked the complex rather than the free ligand
Food wont change natural colour, but the right plate (citrus/vitamin c, tomato/lycopene, carrot, beetroot/beta carotene, papayapineapple enzymes, berries, spinach, avocado, nuts) can support melanin balance, hydration, and antioxidant defense for visible radiance
McNeel RL, Mersmann HJ
You can explore related research at PubMed: Pickart, GHK and tissue remodeling (PMID 9763764)
It is difficult to get reliable amounts of glutathione from diet alone
You recognize that patients, providers, and payers must adapt to changing policies and market dynamics