Five Peptides Every Endurance Athlete Should Understand Frontiers Exploring the beneficial effects of GHK Cu on an experimental model of colitis and the underlying mechanisms GHK Cu as a multifunctional copper peptide: synthesis routes, process engineering and emerging applications Systems Microbiology and Biomanufacturing Springer Nature Link 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 vs NAD+: Which Longevity Peptide Should You Take or Stack? By age 30, your skin produces about 25% less collagen. By 40, that number can reach 40%. This decline affects more than just how your skin looks. It changes how it heals,