I like to look for pre-activated forms of B vitamins such as methyl-folate, methyl-cobalamin (B12), Pyridoxal-5-Phosphate form of B6, and Riboflavin-5-phosphate form of vitamin B2
doi: 10.1053/j.gastro.2017.05.056
Brain function Low levels of vitamin B12 have been linked to a decline in brain function
That's often serotonin, not fatigue
May aid in healing of intestinal anastomoses and fistulas, and shows benefits in models of inflammatory bowel disease, Crohns disease, and ulcerative colitis235
A Nature Scientific Reports 2016 study showed GHK-Cu had no cytotoxicity to human keratinocytes at concentrations up to 5,800 M over 72 hours and did NOT induce inflammatory biomarkers (IL-1, IL-8, HSPA1A, FOSL1) unlike other copper compounds, concluding GHK-Cu has a low potential of inducing skin irritation