Vitamin C

Vitamin C, also known as ascorbic acid, is a water-soluble vitamin found particularly in citrus fruits and green vegetables. It is essential for collagen, catecholamine, and carnitine biosynthesis.

One of its roles is as an antioxidant, that is, it helps to protect cells from damage by oxidative stress and also improves mitochondrial function. Another role is as a cofactor for several enzymes. After absorption, Vitamin C is present throughout the whole body.

Large cross-sectional population studies confirm that vitamin C deficiency is common in humans, affecting 5%–10% of adults in the industrialized world. Moreover, significant associations between poor vitamin C status and increased morbidity and mortality have consistently been observed. However, the absorption, distribution and elimination kinetics of vitamin C in vivo are highly complex, due to dose-dependent non-linearity, and the specific regulatory mechanisms are not fully understood. In addition, the optimal daily intake as well as the typical total body pool of vitamin C during health and disease remain unknown. There are also discrepancies in global vitamin C recommendations, and the various national authorities recommend the minimum amount of vitamin C, however, this is likely not meeting the health needs of various subpopulations. For example, smokers and people with obesity have higher requirements than the general population, and national authorities should reassess their dietary recommendations.



Biology
Vitamin C is found in the whole body, even skin tissue. High levels of vitamin C are found in the eyes, pituitary, adrenal gland, pancreas, liver, spleen and brain. Vitamin C is also found in relative high levels in the bone marrow, muscles and skin. Bone marrow is probably also involved in the vitamin C homeostasis process.

The adrenal gland can inject vitamin C into the blood.

Too much sun exposure may deplete the Vitamin C stores in the skin tissue.

In human disease
Vitamin C is important in mast cell activation disorder for its role in the breakdown of histamine and as a mast cell stabilizer. Vitamin C is also a co-factor in collagen synthesis, making it a potentially important nutrient in Ehlers-Danlos syndrome and other connective tissue disorders. Deficiency of vitamin C may contribute to osteoporosis.

Vitamin C deficiency leads to altered function of procollagen-proline dioxygenase and lysyl hydroxylase enzymes. Each are essential for collagen synthesis and require Vitamin C as a cofactor.

Mast cell activation disorder
Numerous studies have found Vitamin C to be inversely correlated with histamine and that the administration of Vitamin C reduces blood histamine levels. It does this potentially through several mechanisms: by inhibiting mast cell production; by increasing diamine oxidase (an enzyme that breaks down histamine); by inhibiting mast cell degranulation and the release of histamine in the first place (i.e., as a mast cell stabilizer), and by inhibiting histidine decarboxylase (the enzyme that forms histamine).



Ehlers-Danlos Syndrome
A case study found improved wound healing in a patient with vascular Ehlers-Danlos Syndrome who was given high-dose (4g/day) oral vitamin C supplementation for two years. A case study of two patients with Kyphoscoliotic EDS received high-dose Vitamin C (5g/day). After one year, they had reduced bleeding time and improve wound healing, and muscle strength.

Supplementation
Several studies indicates the recovery from Vitamin C depletion will require several months of treatment.

Notable studies

 * 2014, Mitochondrial dysfunction and chronic disease: treatment with natural supplements (Full text)

Learn more

 * Linus Pauling Institute Micronutrient Information Center - Vitamin C