GHK Cu vs NAD+: Which Longevity Peptide Should You Take or Stack? Defy GHK Cu (glycyl L histidyl L lysine) is a naturally occurring copper binding peptide found in human plasma. As levels decline with age, so may its support of the biological processes involved in collagen production, skin GHK Cu Copper Peptide Supplement, Promotes Skin Repair, Reduces Wrinkles CTDE PARIVAR Amazon.com: QUBIT GHK Cu Copper Peptide Supplement for Skin & Hair, Easy to Absorb, Precisely Dosed 90 Vegan Capsules : Health & Household