Look for trials that measure glutathione inside cells (not just in general circulation), like ContinualG's Glyteine glutathione precursor
doi.org/10.63049/OHM.23.11.1 Opportunistic yeasts on stored apples: A One Health perspective Aye Sultan Karakoyun, Nevzat nal, Banu Metin, Esra Yldrm Servi, Bram Spruijtenburg, Muhammed Alper zarslan, Ramazan Gmral, Aylin Den, Macit Ilkit, Hazal Kandemir, Jacques F
But if you just want the fast answer, most research shows GHK-Cu to be the more broadly studied copper peptide for both hair and skin
BPC-157 is a powerful tool
"BPC 157 and the gut-brain axis: Implications for neuroprotection and mental health." Front Neurosci