Unlike fat-soluble vitamins (A, D, E, K), B12 doesnt accumulate to toxic levels from dietary or supplement intake in most circumstances
This barrier usually stops large molecules from entering the brain to protect it
Cell Metab 3(3):153165 Calanna S, Christensen M, Holst JJ, Laferrere B, Gluud LL, Vilsboll T et al (2013) Secretion of glucagon-like peptide-1 in patients with type 2 diabetes mellitus: systematic review and meta-analyses of clinical studies
You don't have to figure this out through trial and error
Simple Benefits You Can Understand: Supports antioxidant protection
Effects of maternal nutrition and one-carbon metabolite supplementation on fetal jejunal morphology and hexose transporter expression in beef cattle