The rise of epidemics in the last 20 years is alarming with the most recent Pandemic resulting in significant mortality and economic loss. A careful review of Vitamin C and other antioxidants provide significant rationale for their use in treatment of common viral infections. Consider that treatment with high-dose vitamin C has been widely utilized by hospital ERs and ICUs to prevent death from SARS-associated pneumonia. [1-16]
Vitamin C is the main systemic extracellular antioxidant, and when given at high doses, either orally (3-10 gm/d) or IV (10-50 gm/d, etc.), can function as an antioxidant to prevent toxicity from ROS and viruses. When oxidized through donating an electron to reduce an ROS, it can be regenerated through a variety of mechanisms, including reducing enzymes and other antioxidants.
Vitamin C can support intracellular antioxidants such as GSH (glutathione) and catalase when the load of ROS is severe. Vitamin C can regenerate GSH when depleted by severe stress. The role of catalase is mainly to reduce hydrogen peroxide and it can function along with SOD and vitamin C to protect cells. However catalase and SOD are large molecules and do not serve the same role as vitamin C (ascorbate) which is a small molecule and can donate electrons to any ROS that it contacts, including oxidized vitamin E and many other molecules that may get damaged by ROS — in either the intracellular or extracellular space. 
Vitamin C also empowers the immune system, promoting chemotaxis, growth, and activity of some immune cells (macrophages, lymphocytes, natural killer cells) allowing the body to more effectively fight an infection. 
Vitamin C has many other roles in which it functions as a specific co-factor for biochemical reactions, for example, in the synthesis of aggrecan and collagen in which it is necessary for the cross linking of long fibers into a 3D matrix, in the absorption of iron, in the metabolism of many essential biochemicals including carnitine and neurotransmitters (e.g. norepinephrine, serotonin). Thus it is essential for recovery from damage caused by viral or bacterial infections, as well as for the normal functioning of the brain and many essential biochemical pathways. 
In addition, when the body is under severe stress, for example, recovering from toxin exposure, surgery, or SARS, the level of vitamin C can be depleted so that it cannot perform its direct or indirect antioxidant functions or its many other specific co-factor roles in biochemical metabolism. This can in turn deplete the other antioxidants, e.g. GSH and vitamin E, which can cause severe oxidative damage inside cells that normally they would prevent.
In high-dose intravenous vitamin C (IVC) therapy, vitamin C is thought to be a pro-oxidant in selective cell types, which allows it to kill specific cell types. This role may function in some types of cancer and also immune hyperinflammation. [18-26]
Overall, vitamin C has a variety of effects (i.e. “pleotropic”) that are not duplicated by intracellular antioxidants. It supports intracellular antioxidants and is necessary as a specific co-factor in many critical biochemical reactions in many organs of the body.
Prevention of viral infections and the various dosing forms
To prevent infection by viruses and bacteria, vitamin C (capsules of ascorbic acid, or crystals of ascorbic acid or sodium ascorbate) dissolved in water or juice has been taken at low and high oral doses (200 mg/d to 10,000 mg/d). The upper limit for an oral dose is defined by the “bowel tolerance” above which the dose is not absorbed in the gut and causes a laxative effect. This dose is set by the body’s need to absorb vitamin C from the gut into the bloodstream. Since the level of vitamin C in the body varies according to the level of oxidative stress, the amount of vitamin C absorbed by the gut also varies.
Typically many individuals can tolerate 1000-3000 mg/day in divided oral doses, which can then maintain a relatively constant level of vitamin C in the bloodstream. Some organs (e.g. liver, brain, eyes, etc) actively transport vitamin C to maintain a higher level than provided by the blood. This state of a relatively high maintained level of vitamin C throughout the body is thought to lower the risk of viral infection by assisting the immune system in detecting and destroying foreign microbes such as viruses that attack the nasopharynx and lungs. In addition, oral doses of vitamin C can directly denature viruses.
Liposomal Vitamin C
Liposomal vitamin C is absorbed by a different mechanism in the gut. The liposomes containing vitamin C can bind directly to the gut cells to release their content of vitamin C which therefore does not require active transport. Thus the maximum level achievable with oral doses of liposomal vitamin C is higher than for regular vitamin C. However, since the absorption mechanism for liposomal vitamin C differs from the active transport of regular vitamin C, both forms can be taken together to increase the level in the bloodstream (up to 400-600 μM), greater than either oral form alone.
High-dose IV Vitamin C
With severe shock, trauma, or sepsis, ascorbate blood levels typically drop to near zero. To restore the ascorbate level, several grams of vitamin C can be administered.  Some IVC protocols have specified doses of 1000-3000 mg as necessary at intervals throughout the day. Other IVC protocols have specified doses as high as 10-20 grams daily for several days or weeks, and even as high as 50- 100 grams daily, when necessary for several days. [6-21]
In severe lung infections, a “cytokine storm” generates reactive oxygen species (ROS) that can be effectively treated with doses of 30-60 g of vitamin C. At the same time the relatively high level of vitamin C can promote an enhanced chemotaxis of white blood cells (neutrophils, macrophages, lymphocytes, B cells, NK cells).
High-dose oral Vitamin C
When the body is stricken with severe stress, oral vitamin C supplements of 20,000 mg/day or even 50,000-100,000 mg/day, in divided doses, can be surprisingly well tolerated because it becomes depleted by helping to alleviate a critical inflammation, e.g. SARS pneumonia. In this case, the level of vitamin C in the bloodstream will not rise much above 200-300 μmol/L, even though under normal circumstances a much lower oral dose would produce the same blood level. The reason is that the vitamin C is oxidized in the process of attacking the inflammatory agent, e.g. viral infection, so that more vitamin C can be absorbed from the gut than normally possible. In this range of high oral doses, vitamin C is considered to function as an antioxidant.
Supplemental vitamin C, both oral and IV is an excellent and relatively simple and inexpensive treatment for both uninfected individuals at home, and critically-ill individuals in the hospital. It has been proven to be effective in treating many different viral and bacterial infections, including SARS pneumonia. With early and high dosing at regular intervals, vitamin C can effectively fight against sepsis, hyper-inflammation, and high virus titer to allow patients to recover quickly. Combined with an overall integrative approach to health management, vitamin C, vitamin D, zinc, and other essential vitamins and minerals can effectively prevent and recover from common infections.
References for Vitamin C
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- Frieden T (2020) Former CDC Chief Dr. Tom Frieden: Coronavirus infection risk may be reduced by Vitamin D. https://www.foxnews.com/opinion/former-cdc-chief-tom-frieden- coronavirus-risk-may-be-reduced-with-vitamin-d.
- Cheng R. (2020) Can early and large dose vitamin C be used in the treatment and prevention of COVID-19? Medicine Drug Discov. In Press, Journal Pre- proof. https://www.sciencedirect.com/science/article/pii/S2590098620300154.
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- Cheng R (2020) NY Hospitals’ use of Vit C is applaudable, but the dosage is too small. https://www.youtube.com/watch?v=NBbbncTR-3k.
- Cheng R (2020) Shanghai Expert Consensus on COVID-19 Treatment, March 21, 2020. Shanghai Expert Group on Clinical Treatment of New Coronavirus Disease. Chinese Journal of Infectious Diseases, 2020, 38: Pre-published online. DOI: 10.3760 / cma.j.issn.1000-6680.2020.0016 http://www.drwlc.com/blog/2020/03/21/shanghai-expert- consensus-on-covid-19-treatment.
- Cheng R (2020) Hospital treatment of serious and critical COVID-19 infection with high-dose Vitamin C. Posted on March 18, 2020 by Dr. Cheng. http://www.drwlc.com/blog/2020/03/18/hospital-treatment-of-serious-and-critical- covid-19-infection-with-high-dose-vitamin-c.
- Lichtenstein K (2020) Can Vitamin C Prevent and Treat Coronavirus? MedicineNet on 03/09/2020. https://www.medicinenet.com/script/main/art.asp?articlekey=228745.
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