The specific function of a vitamin in your body directly affects how a deficiency manifests
B12 (cobalamin) is a single nutrient essential for red blood cell formation, nerve function, and DNA synthesis, whilst B complex provides all eight B vitamins working together to support metabolism and energy production
Retrieved from American Cancer Society
Hackett T-L, Warner SM, Stefanowicz D, Shaheen F, Pechkovsky DV, Murray L, Argentieri R, Kicic A, Stick SM, Bai TR, Knight D: Induction of epithelial-mesenchymal transition in primary airway epithelial cells from patients with asthma by transforming growth factor-beta1
Fatigue that sleep doesn't fix is one of the most common signs of low B12, and one of the most overlooked
United States US4687200A, Ichiro Shirai, "Multi-Directional Switch", published 1987-08-18