Vitamin C

Forms

L-Ascorbic Acid, Mineral Ascorbate (buffered) such as Sodium Ascorbate, Magnesium Ascorbate etc.

Functions

Potent Reducing Agent (Antioxidant)

Prevents molecules in the body (such as Proteins, Fats, Carbohydrates and DNA / RNA) from damage from Free Radicals and Reactive Oxygen Species. Participates in redox recycling of other important antioxidants E.G. Vitamin E. Assists in the synthesis of Collagen, Carnitine, and Catecholamine. Involved in the metabolism of Cholesterol to Bile Acids. Enhances intestinal absorption of non heme iron. Potentially involved in gene expression regulation (See ref below).

Absorption, Storage & Transport:

Plasma vitamin C concentration is tightly controlled by three primary mechanisms: intestinal absorption, tissue transport, and renal reabsorption

Leukocyte (white blood cell) vitamin C is thought to closely reflect tissue stores Recent research demonstrated that human skeletal muscle, a major body pool for vitamin C, is highly labile and more responsive to vitamin C intake than neutrophils or mononuclear cells. According to this leukocyte vitamin C concentration does not accurately reflect skeletal muscle ascorbic acid, and may underestimate muscle tissue ascorbic acid uptake.

Vitamin C is transported through plasma by the sodium-dependent vitamin C transporters 1 & 2 (SVCT1/2) and the glucose transporter isoform 2 (GLUT2).

Conversion

Humans do not possess the enzyme (L-gulonolactone oxidase) required to synthesize Vitamin C making it an essential nutrient for humans.

Cell Receptor:

SVCT1, SVCT2, GLUT

Normal Plasma Level

Normal (homeostatic level) 60 to 80 μmol/L

Plasma concentrations of ascorbic acid ≥50 μmol/L are sufficient to saturate muscle tissue vitamin C. Sub-optimal – plasma levels <50 μmol/L Marginally deficient – plasma levels <28 μmol/L Severely deficient – plasma levels <11 μmol/L Reference Range is approximately 35 – 177 μmol/L.

Sources

Red Pepper, Kiwis, Strawberries, Orange, Brocolli, Grapefruit.

RDA Dose

Adult Male 90mg/day

Adult Female 70mg/day

Supplemental Range: 300mg – 1000mg per day orally, up to 10000mg per day intravenously.

Tolerable upper intake: Tolerable upper intake level (UL) – 2000mg per day.

Toxicity

Risk of kidney stone formation with long term supplementation. Oxylate is a metabolism of Vitamin C.

Deficiency Signs and Symptoms

Severe deficiency:

Scurvy – subcutaneous bleeding, poor wound closure, and bruising easily, hair and tooth loss, bone problems, joint pain and swelling. These symptoms are caused by the weakening of blood vessels, connective tissue, and bone, which all contain collagen. Fatigue results from diminished levels of carnitine, which is needed to derive energy from fat, or from decreased synthesis of the catecholamine norepinephrine. 10mg/day Vitamin C will prevent scurvy. More general deficiency signs: Easy bruising Swollen gums Bleeding gums Slow wound healing Gingivitis (inflammation of the gums) Dry and splitting hair Dry red spots on the skin Rough, dry, scaly skin Nosebleeds Weakened immune system Digestive disorders like leaky gut and autoimmune disease Possible weight gain because of slowed metabolism Swollen and painful joints

Toxicity Signs and Symptoms Toxicity is debatable. Main symptom is gut discomfort and diarrhoea when consuming more than is required.

Therapuetic Uses:

CVD – improves vasodilatation in patients with CHD, CHF, Angina, T2DM, High Cholesterol, High Blood Pressure. Improved vasoldilation occurs at dose of 500mg/day.

Cancer – still under investigation. Diabetes – Common Cold Asthma Lead Toxicity

Nutrient Interactions:

Drug Interactions: OCP and Aspirin lowers plasma and leukocyte Vitamin C concentration.

Vitamin C supplements may interact with Warfarin and other blood thinners. Individuals on anticoagulants should limit their vitamin C intake to 1 gram/day and have their prothrombin time monitored by the clinician following their anticoagulant therapy High dose vitamin C can interfere with certain lab tests. (e.g., serum bilirubin, serum creatinine, and the guaiac assay for occult blood

http://lpi.oregonstate.edu/mic/vitamins/vitamin-c

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2851117/

5 Ways to Increase Vitamin C Levels

http://vitaminc.foundation/forum/viewtopic.php?t=10660

https://www.ncbi.nlm.nih.gov/pubmed/17541511