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Okabayashi, T

Damage to the lining of the stomach and small intestine results in symptoms that range from relatively minor heartburn, nausea, and abdominal pain (affecting 15-40% of NSAID users) to the life-threatening ulceration, perforation, and bleeding (affecting 1-2% of chronic NSAID users) (Vonkeman 2010)

Psychiatry 145 PonzettoC.BardelliA.ZhenZ.MainaF.dalla ZoncaP.GiordanoS.et al (1994)

The most well-studied form is GHK-Cu (glycyl-L-histidyl-L-lysine copper), a naturally occurring tripeptide first identified in human plasma in 1973 by biochemist Loren Pickart

Specifically, look for transparency about peptide purity testing methods, which should be clearly stated on the suppliers website or product label