Vitamin C C deficiency. Beyond that, a role for vitamin C as prevention or treatment for various diseases is disputed, with reviews reporting conflicting results. A 2012 Cochrane review reported no effect of vitamin C supplementation on overall mortality. It is on the World Health Organization's List of Essential Medicines as one of the most effective and safe medicines needed in a health system. The disease scurvy is caused by vitamin C deficiency and can be prevented and treated with vitamin C-containing foods or dietary supplements. It takes at least a month of little to no vitamin C before symptoms occur. Early
Vitamin B12 deficiency anemia specifically, from Imerslund-Grasbeck Syndrome (IGS), a vitamin B12-deficiency caused by mutations in cubilin the cobalamin receptor. The treatment of PA varies by country and area. Opinions vary over the efficacy of administration (parenteral/oral), the amount and time interval of the doses, or the forms of vitamin B (e.g. cyanocobalamin/hydroxocobalamin). More comprehensive studies are still needed in order to validate the feasibility of a particular therapeutic method for PA in clinical practices. A permanent cure for PA is lacking, although repletion of B should be expected to result in cessation of anemia-related symptoms, a halt in neurological deterioration, and in cases