A 2021 systematic review of 16 randomized controlled trials and 6,276 participants (Markun and colleagues, Effects of Vitamin B12 Supplementation on Cognitive Function, Depressive Symptoms, and Fatigue, Nutrients, 2021) found that B12 supplementation does not reliably reduce fatigue in people who are not deficient
However, there may be a link between vitamin B12 and weight loss in people with a B12 deficiency
This depends on several things
On chromosome 1, we observed a significant number of associated variants near the TMCO1 gene, which has been implicated in various disorders, including POAG, craniofacial dysmorphism, skeletal anomalies, and impaired intellectual development syndrome 25
Comprehensive medical assessment before initiating treatment remains essential, as clinical trial populations never fully represent the diversity of health conditions encountered in practice