Immunomodulatory and Antimicrobial Effects of Vitamin C

 1. H2O2 up-regulates Fas expression through the activation of protein tyrosine kinase in ECs.

 2, Various cells express Fas, whereas Fas-L is expressed predominantly in activated T cells.

 3. Vitamin C is an inhibitor of protein tyrosine kinase

 4. Vitamin C suppresses TNF alpha-induced NF kappa B activation by inhibiting I kappa B alpha phosphorylation.

    5.     vitamin C is an inhibitor of tyrosinasse

DHA, the oxidized form of vitamin C, inhibits the activity of IKK汕 and IKK汐 in vitro.

Since intracellular vitamin C inhibited IKK汕(SS/EE)-induced phosphorylation of I百B汐, we examined whether AA would directly inhibit the kinase activity of IKK汕 in a cell-free system. Activated IKK汕 isolated by immunoprecipitation from TNF-汐-treated HeLa cells was immobilized on protein G-agarose beads and then assayed for in vitro kinase activity (). The addition of 1 or 10 mM AA to the kinase reaction mixture had no effect on IKK汕 activity (Fig. (Fig.3A).3A). Under similar assay conditions, 100 mM AA inhibited IKK汕 activity, but this inhibition was abolished when the kinase reaction mixture included dithiothreitol (DTT), suggesting that the inhibitory activity was associated with oxidation of AA (Fig. (Fig.3A).3A). Under nonreducing conditions, AA oxidizes to DHA, which can then be hydrolyzed to oxalic and threonic acid ().

Conversion of AA to DHA by oxidative stress inhibits luciferase activity induced by IKK汕(SS/EE).

To generate intracellular DHA from AA by an oxidative stressor, such as H2O2, we first determined the concentration of H2O2 that had no effect on cell viability or luciferase activity. Cells transfected with IKK汕(SS/EE) and treated with 50 米M H2O2 or not treated with H2O2 showed identical luciferase activity. However, cells loaded with 2.5 mM AA and incubated with 50 米M H2O2 showed an approximately 50% reduction in the luciferase activity (P = 0.004, n = 3, one-tailed t test) (Fig. (Fig.6A).6A). Intracellular AA (2.5 mM) alone had no significant effect (P = 0.5, n = 3, one-tailed t test).

We investigated whether an intracellular generator of ROS, such as dimethoxinaphthoquinine (DMNQ), would also inhibit IKK汕(SS/EE)-dependent luciferase activity in cells preloaded with 2.5 mM vitamin C. The concentration of DMNQ that had no effect on luciferase activity or viability in cells transfected with IKK汕(SS/EE) was found to be 5 米M. Cells loaded with 2.5 mM vitamin C and incubated with 5 米M DMNQ showed significantly reduced luciferase activity (P = 0.003, n = 3, one-tailed t test) (Fig. (Fig.6B).6B). These results indicate that intracellular conversion of AA to DHA inhibits kinase activity of IKK汕(SS/EE), suggesting that DHA functions as a kinase inhibitor in vivo. We propose that in cells loaded with vitamin C and placed under oxidative conditions, AA quenches ROS and transforms into DHA. The DHA generated can leave the cell via facilitative glucose transporters or function as a direct kinase inhibitor as shown here for IKK汐 and IKK汕 (Fig. (Fig.7).7). These processes link oxidative stress to kinase inhibition via the antioxidant, vitamin C.

Schematic representation of the regulation of signaling responses by vitamin C. Vitamin C enters the cell through the glucose transporters as DHA and is rapidly reduced to AA. ROS induces NF-百B signaling responses by activating IKK汕, and AA quenches ROS, inhibiting the activation of IKK汕. Throughout these processes, AA becomes oxidized to DHA, and DHA inhibits IKK汕.

Vitamin C Is a Kinase Inhibitor: Dehydroascorbic Acid Inhibits I百B汐 Kinase 汕

Eur J Microbiol Immunol (Bp). 2019 Oct 3; 9(3): 73每79.

Published online 2019 Aug 16. doi: 10.1556/1886.2019.00016

Immunomodulatory and Antimicrobial Effects of Vitamin C

Soraya Mousavi, Stefan Bereswill, and Markus M. Heimesaat*

Institute of Microbiology, Infectious Diseases and Immunology, Gastrointestinal Microbiology Research Group, Charit谷 - University Medicine Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany


Humans have lost their vitamin C-synthesizing capacities during evolution. Therefore, the uptake of this essential compound from external sources is mandatory in order to prevent vitamin C-deficient conditions resulting in severe morbidities such as scurvy. The potent antioxidant, immunomodulatory, and antiinfectious effects of vitamin C are known since the 1930s. We here (i) review the impact of vitamin C on innate and adaptive immune functions, (ii) provide an overview of its antimicrobial, antibacterial, antiviral, antiparasitic, and antifungal properties, and finally, (iii) discuss vitamin C as an adjunct treatment option for the combat of human infections by bacteria, particularly by emerging multidrug-resistant species.

Keywords: vitamin C, ascorbic acid, immunomodulatory properties, anti-microbial synergy, antibacterial effects


In the 1920s, vitamin C was first identified by the prospective Nobel laureate Albert Szent-Györgyi from Szeged University in Hungary, who unraveled the role of this essential vitamin for the treatment and prevention of scurvy resulting from vitamin C deficiency [1每5]. Vitamin C is the generic term for L-threo-hexo-2-enono-1,4-lactone [6], which constitutes a low molecular weight carbohydrate [1, 7]. Chemically, vitamin C is a gluconic acid lactone derived from glucuronic acid and water-soluble ketolactone with 2 ionizable hydroxyl groups with prominent antioxidant properties [1, 6]. In nature, the 2 essential isomeric molecules of vitamin C are found in equal parts, namely the reduced form D-ascorbic acid and the chemically active and oxidized form L-ascorbic acid [8], which are mutually interchangeable [1, 6, 9, 10]. Vitamin C has a strong potential to reduce distinct molecules while being reversibly oxidized to dehydroascorbic acid (DHA), which can be reduced back to vitamin C exhibiting full biological activity [1, 6, 11]. The intracellular transport of vitamin C takes place in every kind of cells as DHA through glucose transporters (GLUT) following a concentration gradient due to the structure similarity to glucose [8, 12] or actively as ascorbic acid via the sodium-dependent vitamin C transporters (SVCT)-1 and -2 [13, 14] in specific organs such as the small intestines, liver, kidneys, adrenal glands, brain, and retina [15]. Inside the cell, DHA is subsequently reduced to ascorbic acid [16]. Due to these characteristics, vitamin C in involved in several vital processes such as energy metabolism and gene transcription, as well as in regulation of hormonal and epigenetic pathways [17].

The natural sources of vitamin C are citrus fruits, kiwi, mango, strawberries, papaya, tomatoes, green leafy vegetables, and broccoli, for instance [1, 7, 10, 18每20]. Interestingly, the vast majority of vertebrates can synthesize vitamin C from glucose, but a few mammals including guinea pigs and humans have lost this ability due to a lack of L-glucono-污-lactone oxidase, which is necessary for the synthesis of vitamin C in vivo [1, 2, 7, 8, 10, 18, 21, 22]. Therefore, humans need to acquire vitamin C from a diet that supplies 100 to 200 mg of vitamin C per day to cover the general human needs [23, 24] and to decrease the risk of vitamin C-deficient conditions resulting in scurvy, which might be fatal if left untreated [7]. In order to prevent scurvy, a low daily dose of 10 mg is needed [25]. Individuals with scurvy exhibit down-regulated immune responses [26] and are hence highly susceptible towards infections [2, 17]. Given that vitamin C is essentially involved in collagen biosynthesis and repair, the lack of ascorbic acid impairs integrity of basement membranes, mucosal epithelia, and connective tissues, which is causative for the devastating periodontal disease observed in scurvy. Furthermore, the vitamin is required for proper wound healing and bone development, both of which linked to the role of ascorbic acid in collagen synthesis. Other biochemical functions of vitamin C include carnitine synthesis, redox-reactions, production of adrenal steroids and catecholamines, metabolism of amino acids and cholesterol, and iron absorption [5, 27, 28]. 

Several studies revealed that vitamin C possesses antimicrobial properties, thus reducing the risk of infections, and have immunomodulatory functions, particularly in high concentrations [8]. However, one needs to take into consideration that inappropriate storage, processing and preparation procedures of food might result in vitamin C degradation [7], further supporting the demand of appropriate dietary supplementation of this essential vitamin in order to reduce the risk of deficiency. Furthermore, given that vitamin C is water-soluble, intoxication upon excess intake is virtually impossible since vitamin C in concentrations exceeding the daily demands will be excreted via the kidneys [29]. Given its anti-infectious and immunomodulatory properties on one side and the lack of unwanted side effects on the other, vitamin C constitutes a promising antibiotic-independent strategy to combat and/or prevent bacterial (including enteropathogenic) infections. Therefore, this review will focus on the immunomodulatory and antimicrobial effects of vitamin C.

Immunomodulatory Properties of Vitamin C

A critical basal concentration of vitamin C is essential for a normal and well-functional host defense mechanism, and pharmacological application of vitamin C is believed to enhance immune function [30]. Several studies revealed that experimentally induced vitamin C deficiency reduces cellular [31每33] and humoral immune responses [33, 34]. Furthermore, the effect of vitamin C on different immune cell populations has been shown in both experimental in vivo models and in humans [35每38]. In clinical studies, vitamin C treatment of healthy subjects promoted and enhanced natural killer cell activities, lymphocyte proliferation, and chemotaxis [30, 39]. Furthermore, high doses of vitamin C not only stimulated murine immune cells, primarily dendritic cells, to more distinct interleukin (IL)-12 secretion [40], but also activated T and B cell functions [34, 41].


In addition, the observations that vitamin C concentrations in immune cells such as leukocytes are 10- to 100-fold higher than those measured in the plasma [6] and the fact that these cells accumulate vitamin C against a concentration gradient further underline the immunological importance of vitamin C [42, 43] and support its role as crucial player in various aspects of immune cell functions, such as immune cell proliferation and differentiation [17, 44每46], besides its anti-inflammatory properties [47, 48]. Moreover, the newly characterized hydroxylase enzymes, which regulate the activity of the hypoxia-inducible factors (HIF), gene transcription, and cell signaling of immune cells, require vitamin C as a cofactor for optimal activity [49每52].


In the gastrointestinal tract, vitamin C plays an important role as essential micronutrient and antioxidant protecting intestinal cells from inflammatory stimuli [1, 53]. However, in the inflamed mucosa of patients suffering from chronic inflammatory bowel disease (IBD) such as Crohn's disease and ulcerative colitis [54, 55], the mucosal vitamin C concentrations are highly reduced [56]. Furthermore, when applying vitamin C to duodenal explants derived from patients suffering from coeliac disease due to a hypersensitivity reaction to wheat gliadin and similar proteins from rye and barley [57], a decreased secretion of pro-inflammatory mediators in response to gluten could be assessed [58]. In addition, in a small study cohort, intravenous high dose vitamin C application was found to be beneficial as an adjunct treatment option of colorectal cancer [59]. Hence, vitamin C has been shown to exhibit potent immunomodulatory activity in the course of distinct gastrointestinal inflammatory morbidities. In the following paragraph, we will focus on the effect of vitamin C on distinct immune cell populations.


Monocytes and Macrophages

As pivotal components of the innate immune system, monocytes and macrophages are the first line of defense against invading pathogens [60]. The high vitamin C concentrations measured in monocytes [17, 26, 61] underline the regulatory role of this vitamin in monocyte and macrophage functions. In support, an in vitro study revealed that intracellular accumulation of pharmacologic vitamin C concentrations could effectively inhibit apoptotic pathways in human monocytes [16]. Vitamin C may also regulate distinct genes expressed in human macrophages, which are induced by lipopolysaccharide (LPS) via nuclear factor kappa-light-chain-enhancer of activated B cells (NF-百B) activation [62]. Moreover, vitamin C application to monocytes derived from human whole blood diminished secretion of pro-inflammatory cytokines such as IL-6 and tumor necrosis factor (TNF)-汐 [63]. In addition, vitamin C treatment was shown to stimulate and enhance phagocytosis and clearance of macrophages in vitro [17, 33]. Taken together, these findings underline the important role of vitamin C in host defense against pathogens.



The exposure of neutrophils to oxidants inhibits their motility, which is related to oxidation of membrane lipids and affecting cell membrane fluidity [17]. As a potent water-soluble antioxidant, vitamin C can neutralize reactive oxidants and also regenerate cellular and membrane antioxidants such as glutathione and vitamin E (tocopherol) [64]. In order to protect themselves from oxidative damage, neutrophils accumulate millimolar (mM) concentrations of vitamin C [65], resulting in improved cellular motility and migration in response of chemotactic stimuli [66] and, subsequently, in enhanced phagocytosis of microbes and generation of reactive oxygen species (ROS) [17].


In support, oral administration of vitamin C has been shown to enhance neutrophilic functions and to result in increased serum immunoglobulin levels in aging patients [67]. Interestingly, neutrophils isolated from sepsis patients exhibited compromised functional capabilities regarding chemotaxis and the generation of ROS [68, 69]. These phenomena might be associated with decreased vitamin C concentrations in the plasma and leukocytes during infectious diseases and stress conditions [6, 33], which is related to the oxidation of ascorbic acid to DHA, the active form of vitamin C [6, 70].

T Lymphocytes

T lymphocytes as key players in acquired (adaptive) immunity are impacted by vitamin C, as shown by both in vitro [40, 41] and in vivo studies [8]. The development and maturation of murine [37, 71] and human [72] T cells are enhanced in the presence of vitamin C in physiological concentrations, whereas proliferation and viability of T lymphocytes are also affected [37]. In a clinical study with elderly patients who received vitamin C (500 mg/day) versus placebo for one month, an increased T cell proliferation could be assessed in the serum as compared to the placebo group [73]. These results are supported by several in vitro studies with human and murine T cells. In human peripheral lymphocytes, vitamin C application promoted T cell proliferation [72, 74]. In another report, however, a decreased number of human IL-2 producing T cells could be assessed in the presence of vitamin C, whereas TNF-汐 and interferon (IFN)-污 expressing T lymphocytes were not affected [63]. In murine splenic T cell cultures, only high vitamin C levels (0.25每0.5 mM) have been shown to decrease T cell viability and secretion of pro- and anti-inflammatory cytokines such as TNF-汐, IFN-污, and IL-4 by activated T cells, which was not the case following incubation with lower vitamin C concentrations [41]. In support, a recent in vivo study revealed that vitamin C administration during sepsis modified regulatory T cell activity by directly enhancing cell proliferation and by inhibiting the expression of distinct transcription factors, cytokines, and antigens directed against regulatory T cells [75].


Furthermore, T cell activation has been shown to increase expression of SCVT2 [8, 17], which is directly related to a more pronounced cellular uptake of ascorbic acid, further underlining the pivotal role of vitamin C during T cell activation. Given that ROS are formed during T cell activation and act as a second messenger [76每78], it is highly likely that vitamin C affects T cell activation as an antioxidant [8].


B Lymphocytes

B lymphocytes are the main components of adaptive humoral immunity and control the antigen-specific immunoglobulin (Ig) production [37]. Like T cells, B lymphocytes are capable of accumulating vitamin C, whereas in the absence of vitamin C, the viability of B cells derived from murine spleens was shown to be decreased [79], further underlining the essential role of vitamin C in proliferation, viability, and function also of B cells. Interestingly, an in vitro study revealed a slight dose-dependent apoptosis induction in vitamin C-pretreated murine IgM/CD40-activated B cells, whereas lower vitamin C concentrations promoted antioxidant properties in activated B cells and did not affect cell proliferation and expression of distinct surface molecules, such as CD80 and CD86 [34].


Further studies addressed the effect of vitamin C on antibody production by B cells. To investigate if vitamin C might be beneficial for vaccination strategies directed against infectious bursal disease, specific pathogen-free (SPF) chickens received 1 g/mL vitamin C supplementation and showed higher immunoglobulin levels as compared to placebo controls [80, 81]. In support, a clinical trial with healthy male university students revealed that vitamin C supplementation was associated with a significant increase in the serum IgA and IgM concentrations [82]. Thus, these results underline the regulatory effects of vitamin C in B cell proliferation and function.


Natural Killer Cells

Natural killer (NK) cells are arising from the same lymphoid progenitors as T and B lymphocytes [37] and play important roles in the elimination of pathogens including viruses [83]. Proliferation of human NK cells derived from peripheral blood mononuclear cells could be accelerated by co-incubation with vitamin C resulting in higher cell numbers with accurate functional capacity [84]. Furthermore, the cytotoxic capabilities of NK cells could be blocked via platelet aggregation around migrating tumor cells, whereas in vitro vitamin C application increased the cytotoxic activity of NK cells directed against tumor cells [85]. Patients suffering from 汕-thal-assemia major are known to display compromised cytotoxic activity of NK cells [86], which could be rescued by vitamin C application [87]. In healthy subjects, however, the cytotoxic capacities of NK cells could not be further enhanced by vitamin C stimulation [87]. Future in vivo trials need to further unravel the vitamin C related effects on NK cell functions.


Antimicrobial Properties of Vitamin C

As early as the 1930s, vitamin C has been known for its antimicrobial effects directed against Mycobacterium tuberculosis, the infectious agents of human tuberculosis [88每91]. An in vivo study from 1933 revealed that administration of tuberculosis sputum to vitamin C-deficient guinea pigs led to intestinal tuberculosis, whereas the guinea pigs that had received vitamin C-containing tomato juice did not suffer from the disease [92]. Initially it was hypothesized that the antimicrobial properties of vitamin C were due to its pH lowering effect [93]. Another study, however, could prove potent antimicrobial effects of vitamin C directed against group A hemolytic streptococci, even in a nearly pH-neutral environment [94].


Further studies assessed the antibacterial effects of vitamin C against distinct bacterial (opportunistic) pathogens, in more detail, applying microdilution assays. Vitamin C concentrations of 0.31 mg/mL could effectively inhibit Pseudomonas aeruginosa growth in vitro [95]. In addition, vitamin C application at low concentration (0.15 mg/mL) was shown to inhibit the growth of Staphylococcus aureus [95]. Furthermore, vitamin C could even effectively counteract biofilm formation by methicillin-resistant S. aureus (MRSA), displaying low-level resistance to vitamin C (8 to 16 米g/mL) [96]. Interestingly, pH-neutralized vitamin C had only a minor inhibitory effect on S. aureus growth [97]. Furthermore, low concentration of vitamin C (0.15 mg/mL) was shown to have antibacterial effects directed against Enterococcus faecalis [95]. These results are contrasted by another study revealing that the E. faecalis growth was not affected upon co-incubation with 0.22 mg/mL of vitamin C [98]. Thus, the antibacterial effects of vitamin C might be both, bacterial strain and concentration dependent. In support, vitamin C had only a marginal effect on the growth of Escherichia coli ATTC 11775 strain [97]. In combination with lactic acid, however, vitamin C inhibited replication of E. coli O157:H7 strain when incubated in brain heart infusion broth or in carrot juice [99], whereas another study reported that vitamin C even reduced the sensitivity of E. coli MG1655 to streptomycin [100].


Notably, the co-administration of vitamin C could sufficiently enhance the antibacterial effects of other agents such as epigallocatechin gallate directed even against multidrug-resistant bacterial species such as MRSA [101], which also held true for vitamin C in combination with deferoxamine against Gram-positive cocci, such as S. aureus and S. epidermidis, as well as against Gram-negative bacilli, including E. coli, Klebsiella pneumoniae and Proteus mirabilis [102]. Synergistic antibacterial effects could also be observed upon co-administration of vitamin C and quercetin [97], whereas the combination of vitamin C with natural extracts such as pomegranate rind extracts [103] and white tea [104] resulted in enhanced anti-S. aureus properties of the latter.


In the following paragraph, we will focus on the antimicrobial effect of vitamin C on distinct food-borne Gram-negative bacterial pathogens causing frequent human diseases 每 some leading to prominent morbidity.


Anti-Helicobacter Effects of Vitamin C

In an in vitro study, 10 to 20 mg vitamin C per ml could effectively inhibit Helicobacter pylori growth under microaerobic conditions, whereas in an aerobic milieu, vitamin C even promoted H. pylori survival in concentrations ranging from 2 to 20 mg/mL [105]. These observations might be explained by the antioxidant properties of vitamin C, protecting microaerophilic bacteria against toxic effects of ROS. Following one-week treatment of H. pylori-infected Mongolian gerbils with 10 mg vitamin C daily, gastric pathogen loads could be significantly lowered [106]. In support, several clinical studies reported more effective H. pylori eradication upon vitamin C application to infected humans [107每109]. In addition, oxidative stress, apoptotic responses, and decreased cellular viability that had been induced in an H. pylori-infected human gastric adenocarcinoma cell line could be counteracted by vitamin C application in its L-ascorbic acid-2-glucoside form [110].


Anti-Salmonella Effects of Vitamin C

It was reported that vitamin C did not exhibit significant antibacterial activity against Salmonella enterica in cantaloupe puree [111]. In contrast, vitamin C exhibited antibacterial effects against Salmonella Enteritidis in an in vitro study using a broiler-digestive model including the crop compartment, the proventriculus, and the intestine [112]. Interestingly, in the crop compartment, vitamin C alone could even more effectively inhibit Salmonella growth inhibition, as compared to a combination with curcumin and boric acid, whereas conversely, in the proventriculus and intestine, only the combination of vitamin C, curcumin and boric acid exhibited significant antibacterial activity against S. Enteritidis [112]. Furthermore, a recent study revealed that the antibacterial effect of vitamin C against S. enterica subsp. enterica serovar Typhi and Vibrio fluvialis could be enhanced when applied in a combination with linalool and copper [113]. The effect of this triple combination on bacterial morphology was demonstrated by scanning electron microscopy using V. fluvialis, which showed severe membrane damage, whereas no toxicity could be assessed in human embryonic kidney (HEK293) cells at synergistic concentrations (16.3 米M, 8 mM, and 1.298 mM vitamin C) [113].


Anti-Campylobacter Effects of Vitamin C

Supported by several in vitro studies in the 1980s, vitamin C in a combination with linalool and copper was shown to exhibit synergistic activities against Campylobacter jejuni [113]. Fletcher et al. demonstrated the inhibitory effect of vitamin C (0.5 mg/mL) on C. jejuni growth in vitro, mainly caused by vitamin C oxidation products such as L-dehydroascorbic acid or L-diketogulonic acid [114]. Interestingly, vitamin C in concentrations below 1 mM even stimulated C. jejuni growth, whereas 5 mM of vitamin C killed the bacterial cells [115]. This bactericidal effects of vitamin C was further confirmed on C. jejuni-contaminated turkey meat, given that C. jejuni death rates increased in vitamin C treated samples (5 mmol/kg) [116]. To date studies addressing potential anti-C. jejuni effects of vitamin C in vivo are missing, however.

Anti-Viral, Anti-Parasitic and Anti-Fungal Effects of Vitamin C

The antimicrobial properties of vitamin C are not restricted to bacterial cells. Several studies reported that vitamin C, especially in form of DHA, inhibited the replication of herpes simplex virus type 1, poliovirus type 1 [117], and influenza virus type A [117, 118]. Moreover, vitamin C effectively inactivated the rabies virus in vitro [119]. Also, anti-parasitic effects of vitamin C could be demonstrated. A previous in vivo study revealed reduced parasite counts in Trypanosoma cruzi [120] and Plasmodium yoelii 17XL [22]-infected mice, when treated with vitamin C as compared to placebo control animals, which might also be due to the immunomodulatory properties of vitamin C. In support, another study demonstrated that high doses of vitamin C application (i.e., 8.56 mg/kg body weight) can dampen malarial parasitaemia in infected mice, but surprisingly, the co-administration of vitamin C and the anti-malaria drug artemether [121] reduced parasitic clearance in Plasmodium berghei malaria infected mice as compared to artemether application alone [122]. In addition, anti-fungal effects of vitamin C have also been reported. One study showed vitamin C-associated inhibition of Hsp90-mediated morphogenesis in Candida albicans, whereas in another study, vitamin C exhibited low-level fungistatic activities against C. albicans [95]. Thus, vitamin C possesses potent antimicrobial properties reducing pathogenicity of bacteria, viruses, parasites, and fungi.


Summary and Conclusions

For a few vertebrate species including humans having lost their capacities to synthesize vitamin C themselves during evolution, the uptake of this essential compound from external sources is mandatory in order to prevent from vitamin deficient conditions resulting in severe morbidities such as scurvy. However, vitamin C supplementation is well tolerated and safe, given a virtual absent risk of intoxication upon uncompromised renal function. The biological role of vitamin C is related to its reversibly oxidized form and is involved in a multitude of both enzymatic and non-enzymatic processes. Additionally, vitamin C is a powerful antioxidant compound directed against free radicals and ROS. Leukocytes including lymphocytes can actively accumulate vitamin C against a concentration gradient, which underlines not only vitamin C dependent functional but also developmental immune cell features. In fact, vitamin C has a pivotal impact on both innate and adaptive immune responses. Vitamin C is also involved in bacterial metabolism. It is known that several bacteria can ferment vitamin C, whereas the presence of this vitamin exposes others to oxidative stress, which may result in bacterial growth inhibition. The potent antibacterial effects of vitamin C are, at least in part, due to its low pH and thus milieu-modifying properties. Notably, vitamin C is able to inhibit the growth of S. aureus and streptococci even under neutral pH conditions. Potent growth-inhibitory effects against multi-drug resistant (MDR) bacteria such as MRSA and proven synergistic effects with natural or synthetic antibiotic compounds open novel avenues for the combat of infections with emerging MDR bacterial species. However, both in vitro and in vivo (experimental and clinical) studies are needed to better understand the molecular mechanism of antimicrobial synergies. This applies not only to bacterial, but also to viral, parasitic, and fungal infections.



List of Abbreviations:


CFU: colony-forming units


DHA: dehydroascorbic acid


GLUT: glucose transporter


HIF: hypoxia-inducible factors


IBD: inflammatory bowel disease


IFN: interferon


Ig: immunoglobulin


IL: interleukin


LPS: lipopolysaccharide


MDR: multi-drug resistant


MRSA: methicillin-resistant Staphylococcus aureus


NF-百B; nuclear factor kappa-light-chain-enhancer of activated B cells


NK cell: natural killer cell


ROS: reactive oxygen species


SPF: specific pathogen-free


SVCT: sodium-dependent vitamin C transporter


TNF: tumor necrosis factor

Immunomodulatory and Antimicrobial Effects of Vitamin C

Biochemistry, November, 2002

Vitamin C suppresses TNF alpha-induced NF-kappa B activation by inhibiting I Kappa B alpha phosphorylation

Extracellular stimuli signal for activation of the transcription factor NFkappaB, leading to gene expression regulating processes involved in immune responses, inflammation, and cell survival. Tumor necrosis factor-alpha (TNFalpha) activates NFkappaB via a well-defined kinase pathways involving NFkappaB-inducing kinase (NIK), which activates downstream multisubunit IkappaB kinases (IKK). IKK in turn phosphorylates IkappaB, the central regulator of NFkappaB function.

We found that intracellular vitamin C inhibits TNFalpha-induced activation of NFkappaB in human cell lines (HeLa, monocytic U937, myeloid leukemia HL-60, and breast MCF7) and primary endothelial cells (HUVEC) in a dose-dependent manner.

Vitamin C is an important antioxidant, and most cells accumulate ascorbic acid (AA) intracellularly by transporting the oxidized form of the vitamin, dehydroascorbic acid (DHA). Because ascorbic acid is a strong pro-oxidant in the presence of transition metals in vitro, we loaded cells with vitamin C by incubating them with DHA. Vitamin C-loaded cells showed significantly decreased TNFalpha-induced nuclear translocation of NFkappaB, NFkappaB-dependent reporter transcription, and IkappaBalpha phosphorylation.

Our data point to a mechanism of vitamin C suppression of NFkappaB activation by inhibiting TNFalpha-induced activation of NIK and IKKbeta kinases independent of p38 MAP kinase. These results suggest that intracellular vitamin C can influence inflammatory, neoplastic, and apoptotic processes via inhibition of NFkappaB activation.

Vitamin C suppresses TNF alpha-induced NF-kappa B activation by inhibiting I Kappa B alpha phosphorylation | Request PDF

More doctors need to read this: Studies show a link between vitamin C levels and inflammatory markers

This study took a look at more than 3,000 men who were between 60 and 79 years of age that hadn*t been diagnosed with diabetes, stroke, or heart attack. They were questioned on the foods they ate concerning their vitamin C intake and then their blood samples were checked for inflammatory market C-reactive protein (C-RP), plasma levels of vitamin C, and additional markers of inflammation.

Researchers discovered that those who took in more vitamin C and had higher plasma levels of the vitamin ended up with lower levels of inflammation markers like C-reactive protein (CRP).  In fact, the men who were in the highest one-fourth of participants for vitamin C levels had an incredible 44% lower risk of elevated CRP than men in the lowest fourth.

Warning : What chronic inflammation can do to your health
Although inflammation is a body process designed to help the body heal itself, chronic inflammation brings with it great risk of certain health problems. Previous studies in the past have shown that blood indicators of inflammation 每 such as homocysteine, fibrinogen, and C-reactive protein 每 can be predictive of heart disease and heart attack.

CRP is a critical inflammatory marketer indicated a higher risk for abnormal arterial clotting and the destabilization of plaque within the arteries
. Either of these issues can result in an acute heart attack, and additional studies have shown that people with high levels of CRP are three times more likely to die from having a heart attack.

High levels of chronic inflammation seem to also indicate a higher risk of developing cancer, and actually plays a part in tumor development. Research uncovered that the amount of inflammation in your body can predict the risk of developing, and surviving, various types of cancer.

Although the best way to fight inflammation with vitamin C*s antioxidant powers is to get it from the foods you eat, a supplement can help you ensure you*re getting enough of this essential vitamin. Just remember, the ※recommended daily allowance§ of vitamin C is only 90mg for men and 75mg for women.

But, as many integrative healthcare providers will tell you: the sicker you are, the more vitamin C you need.

Vitamin C at Higher Levels Can Defeat Inflammation | NaturalHealth365

Coronavirus and Vitamin C
Is vitamin C going to prevent you becoming infected with the deadly Coronavirus? Is vitamin C a potential cure for the Coronavirus? Vitamin C (also known as ascorbic acid) has been known as one of the most potent immune system boosters in the world, but can it really help you fight this new Coronavirus?

Let*s see some analysis, scientific research and evidence below, and let*s find out how you can maximise the use of Vitamin C and other supplements to protect yourself from the virus.

Coronavirus and vitamin C 每 when 2 titans of the molecular world clash

What do we know about Coronavirus and Vitamin C?
There are a few facts that we know so far about the Coronavirus and Vitamin C:

The Coronavirus is an enveloped non-segmented positive-sense RNA virus belonging to the family Coronaviridae [Ref]
It spreads through air droplets exhaled by an infected person, or animal [Ref]
It*s highly contagious 每 just being in a room with an infected person can get you infected [Ref]
It can develop into pneumonia, called ※Novel coronavirus-infected pneumonia§ (NCIP) the fatality rate of those who get pneumonia is 4.3% [Ref]
The severe and deadly cases were reported mostly on elderly people or people with weak immune system [Ref]
The total fatality rate in China is about 2.1% 每 which means, that from every 100 infected people, about 2 will die [Ref]
As a pathogen, it has similar characteristics as the HIV 每 scientists even started trials of treatment with HIV drugs [Ref]
There is no treatment for Coronavirus [Ref], the only way you can get healed is to have a strong immune system.
Vitamin C
It is an extremely potent antioxidant and immune system booster [Ref]
Humans are one of the few mammals that are unable to produce vitamin C with their bodies [Ref]
It is a non-toxic substance, even in extreme mega-doses [Ref]
High dosage of vitamin C proved extremely effective in the treatment of the seasonal flu (that kills about 60,000 people every year in the US alone) [Ref]
High dosage of vitamin C was successfully used in treating even viral pneumonia [Ref]
Vitamin C, in combination with some antibiotics, can kill cancer cells [Ref], [Ref], [Ref]
Vitamin C reduces the growth and advancement of the Human Immunodeficiency Virus (HIV) [Ref]
Other extremely good articles about Vitamin C:
Treating Illness With Vitamin C
Vitamin C 每 The Overlooked Miracle Drug
Vitamin C: More Than What Meets The Eye
Vitamin C, Linus Pauling was right all along
Can vitamin C help you with Coronavirus?
There is absolutely no doubt about this! Looking at the real, scientific and well documented evidence above, we can clearly say that Vitamin C is more than what meets the eye, as stated by Carole S. Ramke in one of the links above.

It is a super-substance that dramatically increases and enhances the functions of the human cell, and especially those associated with the functioning of the human immune system. It is a turbocharger for immune system, and then some.

As we have seen in the scientific research above (yes, I must emphasise ※scientific research§ many times just to remind the skeptics), this vitamin taken in extreme dosages (about 20-40 times the daily recommended dose) is capable of fighting deadly viruses such as HIV, viral pneumonia, and it can even help killing cancer cells when combined with certain antibiotics.

These are facts, backed by strong scientific evidence and research. Black on white!

What we have also learnt above, is that vitamin C is absolutely safe to take, even in mega-dosages 每 one of the worst side-effects that a healthy person can have is a slight laxative effect 每 a slight diarrhoea.

From here onwards, it is very simple to do the maths.

Coronavirus: your only chance is to have a strong immune system.
Vitamin C: Ultra-efficient immune system booster.
It cannot be anymore simpler than this. It*s as simple as 5 每 2 = 3. Sorry, but I have to say: only the dumb would argue with the above.

By boosting up your immune system with vitamin C, you are reducing the risk of being infected with the coronavirus, and if you are infected, you are reducing the risk of having severe conditions from the virus.

Mega-dosing Vitamin C is a very effective way to protect yourself from the Coronavirus, and to speed-up the recovery, if infected. As a strong immune system is the only effective way to protect yourself from the virus as of today, there is no other option available than to have an extremely strong immune system. This can be achieved by taking high doses of vitamin C, as studies and research has shown.

How much vitamin C should I take to fight the Coronavirus?

The dosage of vitamin C is the key factor in your efforts to combat the Coronavirus, or to avoid being infected. This will have to be a super-dose!

As opposed to the daily recommended daily intake value of just 90 milligrams per day [Ref] (yes, that*s just 0.09 grams), many studies and experts suggest that we need at least 500 milligrams per day just for our body to function normally, under no stress conditions [Ref].

However, we are fighting the novel Coronavirus here.

The daily dosage of vitamin C should start at 2 grams (yes, that*s 2000 milligrams, more than 20 times the daily recommended value), and increased to 3-4 grams (3000-4000 milligrams) a day within 3 days of starting the supplementation. A typical multivitamin tablet contains somewhere around 65-100 milligrams, but we*ll obviously need more than that.

The strongest vitamin C tablets that we could find as being widely available are the 1500 milligram ones (1.5 grams), and you can buy them online with a simple Google search, or from bodybuilding supplement stores.

Start the supplementation with one and a half tablet daily, for 2 days, then you can increase to 2 tablets/day, which will give your system 3000 milligrams of vitamin C, to ward off the Coronavirus.

If you want to go to the extreme, you can take 3 or 4 tablets per day, giving you up to 6 grams of vitamin C per day. As mentioned above, and as seen in the studies and medical papers referenced, vitamin C is not dangerous and not toxic even in high doses. Whatever your body can*t use, will be eliminated through urine.

Research has shown that the body can absorb around 2000-3000 milligrams (2-3 grams) per day, of vitamin C, and this absorption rate can depend on each individual, and this limit is due to the way the digestive system works.

There is a way to take in way more vitamin C in your body, way more than 2-3 grams, by bypassing your digestive system.

Intravenous vitamin C and Coronavirus
As mentioned in the paragraph above, there is a certain limit on how much vitamin C your body can absorb each day, and this limit is due to the fact that the vitamin needs to go through your digestive system, then get absorbed into your blood through your intestines.

This way, only about 2-3 grams of vitamin C can be absorbed by your body, into your bloodstream.

In order to get the best out of the vitamin C supplementation, and especially if you are in a zone of high risk of contamination with the Coronavirus, you might want to go to the extreme, and bypass your digestive system, to make sure you can get 10-20 grams of vitamin C into your system, to maximise the potentiality of this super substance.

You can get high doses of vitamin C directly into your bloodstream, by intravenous vitamin C administration. This is simply vitamin C on drips, in one of your arm*s veins.

Unfortunately this is more complicated than just buying the tablets online, and need to be done in a controlled and medical environment.

We have found that in the UK, for example, there are some health centres providing this service, but it costs up-to £225 per administration (yes, that would be £225 per day if you want to take in 25 grams a day):

In the US, it can be even more expensive, or more difficult to get this service, as seen in this forum discussion:

Another alternative would be to find a nurse, or if you have a friend who is a nurse, and then buy the vitamin C yourself, from places such as (disclaimer: NOT affiliated with the links below):

What are the risks of high vitamin C dosage

Endless studies have shown that vitamin C is safe even in incredibly high megadoses. On the website, there is a study cited where they have concluded that doses as high as 1.5g/kg were safe on healthy humans [Ref].

This means, that a person who weights 75kg, is able to safely take doses of up-to 112 grams of vitamin C (yes, that*s 112,000 milligrams, in contrast with the 90 milligrams of daily recommended value) 每 this can only be achieved intravenously, as it*s impossible to take this in via the digestive system.

Endless studies have shown that vitamin C is absolutely non-toxic, even at extreme doses, and in the worst case scenario, you will have develop mild side effects such as diarrhoea or mild nausea [Ref].

Is vitamin C an actual cure for Coronavirus?
Vitamin C is not a direct cure for the novel coronavirus. All it does, is it boosts up your immune system to extreme levels, so that it (the immune system) can fight the coronavirus, minimise the symptoms, and speed up recovery.

Unfortunately the strong immune system is the only option that we have currently, and we have to do whatever it takes to keep it in great shape. Vitamin C seems to be one of the best substances that can do this, without having any risk or major side effect.

But are there any other substances that you can use to make sure your immune system is in good shape?

What other supplements can I use to fight or protect myself from the Coronavirus?
As our main goal is to boost the immune system, apart from vitamin C, we have some other extremely potent supplements that we can use, that will ensure that our body and immune system is ready to fight the Coronavirus.

And all is backed by scientific evidence, research, and studies. Let*s see a list of other supplements that you can use to fight the Coronavirus, most of them are also used by elite athletes around the world to keep their bodies strong and to help with recovery after intensive workouts, ordered by priority and effectiveness:

One of the well researched and well known amino-acids that plays an important role in the body*s immune system. [Ref] [Ref]
This is a non-essential amino-acid, or more accurately, a conditionally essential amino acid 每 under non-stress conditions it*s considered non-essential, which means your body can produce it by combining other amino-acids, however#
# if the individual is exposed to stress conditions, such as viruses, bacteria, or intense physical activities, it becomes an essential amino-acid, as the body won*t be able to produce it in large quantities enough [Ref]
L-Arginine [Ref]
Bovine colostrum [Ref]
Ultra-strength multi-vitamins and minerals [Ref]
MSM [Ref]
BCAA [Ref]
What else can I do to prevent or fight the Coronavirus?
Once you have taken the vitamin C and other supplements from above to increase your immune system and get it ready for the Coronavirus, there some other important things that you can do to keep a healthy body and a strong immune system. Let*s enumerate a few ones below:

Sleep well, and enough
The body recovers the most while you*re asleep 每 this is when your immune system can work at it*s full potential, so make sure you*ll get enough rest, between 7 and 8 hours a day [Ref] [Ref] [Ref] [Ref]
Make sure that not only you sleep enough hours, but also, at the right time. The body produces it*s most important hormones between 10 p.m. and 01:00 a.m., so make sure that you are already asleep during this period
Eat healthy and nutritious food
Exercise regularly, and intensively, even it it*s just for 20 minutes a day
Be positive, and avoid arguments and negative emotions [Ref]

The bottom line

Coronavirus can potentially be stopped and beaten with a healthy and strong immune system, just like most of other similar diseases.

This new virus seems to be more unapologetic with people who have their immune system weakened, or people that have underlying health conditions.

The best thing that we can do to fight off the coronavirus is to maximise the resources available to create a strong and responsive immune system 每 and one of the most potent supplements to achieve this is definitely vitamin C.

Stay healthy, and stay safe.

Coronavirus and Vitamin C - Ovulation Calculator

Int Immunopharmacol. 2019 May;70:387-395. doi: 10.1016/j.intimp.2019.02.031. Epub 2019 Mar 8.
Different doses of vitamin C supplementation enhances the Th1 immune response to early Plasmodium yoelii 17XL infection in BALB/c mice.

Qin X1, Liu J2, Du Y3, Li Y4, Zheng L4, Chen G5, Cao Y6.
Author information

Vitamin C (ascorbate) is maintained at high levels in most immune cells and can affect many aspects of the immune response. Here, we evaluated the effect of vitamin C supplementation on the immune response to Plasmodium yoelii 17XL (P. yoelii 17XL) infection in BALB/c mice. Two orally administered doses (25 mg/kg/day and 250 mg/kg/day) of vitamin C significantly reduced levels of parasitemia during the early stages of P. yoelii 17XL infection. The numbers of activated Th1 cells and macrophages in the groups receiving vitamin C supplementation were both higher than those in the untreated group. Meanwhile, vitamin C administration reduced the levels of tumor necrosis factor 汐 secreted by splenocytes. Vitamin C also regulated the protective anti-malarial immune response by increasing the number of plasmacytoid dendritic cells, as well as the expression of dendritic cell maturation markers, such as major histocompatibility complex class II and cluster of differentiation 86. In conclusion, the doses of vitamin C (25 mg/kg/day, 250 mg/kg/day) during the early stages of malaria infection may better enhance host protective immunity, but have no dose dependence.

Copyright © 2019. Published by Elsevier B.V.

Effects on immune response; Plasmodium yoelii 17XL; Vitamin C

PMID: 30852294 DOI: 10.1016/j.intimp.2019.02.031
[Indexed for MEDLINE]

Different doses of vitamin C supplementation enhances the Th1 immune response to early Plasmodium yoelii 17XL infection in BALB/c mice. - PubMed - NCBI