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 A deficiency and lymphocytes. Suppression of these result in a lack of immune reaction if pathogens become present in the body and consequently a greater susceptibility to incubation of disease. VAD and infections aggravate each other, so with infection, vitamin A levels are depleted, which in turn reduces intestinal absorption of vitamin A. Very often seen with VAD is protein energy malnutrition, in which the synthesis of retinol binding protein (RBP) is decreased, consequently the uptake of retinol is reduced. This leads to an inability to use any vitamin A present as the RBP is absent, so the retinol cannot be transported