do doctors prescribe ghk cu GHK-CU – Research Peptide GHK-Cu vs NAD+: Which Longevity

The DPYD enzyme keeps the proper balance of the nucleotides in the cells

A number of factors, including age, diet, and underlying medical conditions, can impact your body's capacity to metabolize and absorb B12

Blinks JR, Prendergast FG, Allen DG (1976) Photoproteins as biological calcium indicators

That reasoning is legitimate as a hypothesis, but it is worth flagging early that the body makes less of it with age is not by itself evidence that adding it back least of all by injection produces a cosmetic benefit

But even for colored peptides, a change from the original color is a warning sign

Public Health Nutrition