Low-dose protocols (0.250.5mg daily) are derived from studies where systemic copper peptide administration at 24 mcg/kg demonstrated follicle-stimulating activity without elevating serum copper above the normal range (70140 mcg/dL)
Wang X-Y, Qu M, Duan R, Shi D, Jin L, Gao J, et al
"Heavy Metals Toxicity and the Environment." EXS , August 2014, "How You Can Avoid Low-Level Arsenic in Rice and Chicken." Cleveland Clinic, February 2018, Always be in the know
A double-blind, placebo-controlled trial in frail elderly people without cognitive impairment found significant improvements in cognition from baseline with NAC, 1800 mg per day for 6 weeks, whilst there were no improvements in the placebo group