Vitamin CVitamin C, also known as L-ascorbic acid, is the primary water-soluble antioxidant in plasma and tissues. It is a potent reducing agent, meaning that it readily donates electrons to recipient molecules. Related to this oxidation-reduction (redox) potential, two essential functions of vitamin C are as an antioxidant and as an enzyme cofactor.

Vitamin C protects important molecules in the body, such as proteins, lipids, carbohydrates, and nucleic acids (DNA and RNA), from damage by free radicals and reactive oxygen species (ROS), generated during normal metabolism, by active immune cells, and through exposure to toxins and pollutants. Vitamin C also participates in redox recycling of other important antioxidants; for example, it regenerates vitamin E from its oxidized form.

Most animal species require relatively large amounts of vitamin C on a daily basis and have the ability to synthesize vitamin C endogenously, but that’s not true for humans. Anthropoid primates such as apes and humans, as well as guinea pigs, and some species of bats and birds have lost the ability to endogenously synthesize L-ascorbic acid, so it is an essential dietary component for these species and must be regularly obtained from the diet (1, 2). Vitamin C is naturally present in many fresh fruits and vegetables, but diminished by heat and cooking.

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Vitamin C

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by Emerson Ecologics

Vitamin C has a number of key metabolic roles in activating other vitamins and cofactors as well as in the synthesis of neurotransmitters. (3) Additionally, it plays a vital role in immune system function. It supports cardiovascular health, cognitive function and bone health including mitigating the risk of developing degenerative joint problems (4). Vitamin C also enhances the absorption of iron.With regard to immune function, vitamin C has key roles in generating ROS – Reactive Oxygen Species used to kill invading microbes. It is an important antioxidant function specifically in the regeneration of glutathione, the key intracellular antioxidant. Vitamin C has been shown to both decrease the risk of getting certain infections and also improve immune system function in fighting infections. (5-9).

USESVitamin C deficiency leads to scurvy, which is rarely seen today; however, vitamin C supplementation remains indicated to prevent deficiency in persons at risk due to poor dietary intake. Additionally, it may be recommended in combination with various iron supplements to improve the body’s absorption of iron in the treatment of anemia. It may also be recommended for wound healing due to its critical role in collagen synthesis. There has been long standing interest and use of vitamin C for various immune conditions due to its antioxidant activity. Intravenous vitamin C is used in the clinical setting for various medical conditions including acute infectious illness.

USUAL DOSE / ADMINISTRATIONRDA replacement doses of Vitamin C are 65-95 mg per day. Doses up to 2,000 mg per day are frequently given for antioxidant support. Much higher doses up to 10,000+ mg per day are occasionally used in the setting of acute infections. Vitamin C is most commonly given orally and available in tablet,capsule and powder forms.

Liposomal dosing systems are also gaining popularity. There is little scientific evidence that any one form is better absorbed or more effective than another. Vitamin C is used intravenously in the clinical setting for various protocols.One hundred percent absorption efficiency is observed when ingesting vitamin C at doses up to 200 mg at a time. Higher doses (>500 mg) result in fractionally less vitamin C being absorbed as the dose increases. Once plasma vitamin C concentrations reach saturation, additional vitamin C is largely excreted in the urine. Notably, intravenous administration of vitamin C bypasses absorptive control in the intestine such that very high concentrations of vitamin C can be achieved in the plasma; within a few hours, renal excretion restores vitamin C to baseline plasma concentrations.

ACTIVE INGREDIENTS/ BIOCHEMISTRY:Vitamin C as the purified compound ascorbic acid is a charged molecule. It may also be given in its protonated form- ascorbate. As its name would indicate it is a weak organic acid in the nonprotonated form.(10)

MECHANISMS OF ACTION:Vitamin C has a variety of different roles in the body from regulating and enhancing immune function to participating in collagen synthesis. In its roles in redox metabolism, vitamin C is reversibly oxidized to dehydroascorbic acid. It’s ability to help in the regeneration of glutathione to the reduced form is key as an antioxidant, especially in the intracellular milieu throughout the body.In collagen synthesis vitamin C acts as a cofactor in the generation of 4-hydroxyproline and also serves in this role in the synthesis of other proteins.In regard to immune function the oxidation-reduction properties provide potent chemical weapons for white blood cells and other immune cells to use in the defense of the body against invading organisms of many types.

Vitamin C

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CONTRAINDICATIONS / SIDE EFFECTS:There are no absolute contraindications to the use of Vitamin C since it is an essential nutrient Excessive vitamin C should generally be avoided in cases of iron overload because it increases iron absorption. Supplemental vitamin C increases urinary oxalate concentrations, but whether an increase in urinary oxalate elevates the risk for kidney stones is not yet known and therefore moderation is recommended in those with elevated risk for kidney stones.The most commonly observed side effect of high dosing is GI upset/intolerance and diarrhea. This can occur with moderate doses of even 500 mg in some people, but most people tolerate vitamin C without trouble. If digestive irritation occurs with a single bolus dose, the dose can be divided to improve tolerance. Irritative urinary symptoms, headache, and insomnia along with other less frequent side effects have been observed. Some studies suggest that low dose Vitamin C long term protects against cataracts but that higher doses of 1,000 mg per day or more may increase the risk.

REFERENCES1. Drouin G, Godin J-R, Pagé B. The genetics of

vitamin C loss in vertebrates. Curr Genomics. 2011;12(5):371-378.

2. Chambial S, Dwivedi S, Shukla KK, John PJ, Sharma P. Vitamin C in disease prevention and cure: an overview. Indian J Clin Biochem. 2013;28(4):314-328.

3. Li H, Zeng C, Wei J, et al. Associations between dietary antioxidants intake and radiographic knee osteoarthritis. Clin Rheumatol. 2016;35(6):1585-1592.

4. Gorton HC, Jarvis K. The effectiveness of vitamin C in preventing and relieving the symptoms of virus-induced respiratory infections. J Manipulative Physiol Ther. 1999;22(8):530-533.

5. Combs GF. The Vitamins. 3rd ed. Academic Press; 2007.

6. Hemilä H. Vitamin C and infections. Nutrients. 2017;9(4):339.

7. Boretti A, Banik BK. Intravenous vitamin C for reduction of cytokines storm in acute respiratory distress syndrome. PharmaNutrition. 2020;12(100190):100190.

8. Rml CB, M B, Pe M. The antiviral properties of vitamin C. Expert Rev Anti Infect Ther. 2020;Feb;18(2):99-101.

9. Mousavi S, Bereswill S, Heimesaat MM. Immunomodulatory and antimicrobial effects of vitamin C. Eur J Microbiol Immunol (Bp). 2019;9(3):73-79.

10. Figueroa-Méndez R, Rivas-Arancibia S. Vitamin C in health and disease: Its role in the metabolism of cells and redox state in the brain. Front Physiol. 2015;6:397.

Disclaimer: Emerson Ecologics does not distribute any products to treat or prevent diseases related to the various forms of influenza or coronavirus. The scientific articles provided are for informational and research purposes only and are not a substitute for your professional judgment. We expressly deny that the information being provided is intended to assist in the cure, diagnosis, prevention, or treatment of influenza or coronavirus-related diseases, including but not limited to COVID-19, MERS, or SARS. You should always exercise your professional judgment when reviewing scientific literature.