Vitamin C contributing to the more severe symptoms of scurvy. More generally, the biochemical role of vitamin C is to act as an antioxidant (a reducing agent) by donating electrons to various enzymatic and non-enzymatic reactions. Doing so converts vitamin C to an oxidized state - either as semidehydroascorbic acid or dehydroascorbic acid. These compounds can be restored to a reduced state by glutathione and NADPH-dependent enzymatic mechanisms. In plants, vitamin C is a substrate for ascorbate peroxidase. This enzyme utilizes ascorbate to neutralize toxic hydrogen peroxide (HO) by converting it to water (HO). Scurvy is a disease resulting from a deficiency
Vitamin A a result of alcohol consumption during pregnancy is the elucidated mechanism for fetal alcohol syndrome and is characterized by teratogenicity closely matching maternal vitamin A deficiency. A 2012 systematic review found no evidence that beta-carotene or vitamin A supplements increase longevity in healthy people or in people with various diseases. A meta-analysis of 43 studies showed that vitamin A supplementation of children under five who are at risk of deficiency reduced mortality by up to 24%. However, a 2016 Cochrane review concluded there was not evidence to recommend blanket Vitamin A supplementation for all infants between one and six months