Vitamin C has long been recognized for bolstering immune health and helping individuals protect themselves against influenza. Furthermore, its use has been known to lessen duration and severity of respiratory infections like COVID-19.

Vitamin C is a water-soluble vitamin that acts as an antioxidant and neutralizes reactive oxygen species, protecting biomolecules such as proteins and membranes from damage caused by reactive oxygen species. Furthermore, vitamin C plays an integral part in neutrophil apoptosis to clear spent cells away from inflammation sites quickly, helping prevent excessive tissue damage.

1. Boosts Natural Killer Cells

Vitamin C supports natural killer cells’ efforts in fighting pathogens in the body and aids production of interferons – compounds which stimulate white blood cells to attack invaders such as microbes and viruses – thus optimizing immune cells’ defense system and shortening time needed for detection and neutralization of invaders.

Vitamin C also supports the function of phagocytes, white blood cells that surround and digest pathogens and dangerous debris, so as to protect the immune system. This is particularly essential in cases of septic shock which is characterized by catastrophic failure of circulatory, metabolic, and immune systems leading to high hospital mortality rates.

Studies have demonstrated that patients suffering from septic shock have lower plasma vitamin C levels than healthy individuals, with intravenous vitamin C administration shown to boost these levels, helping patients experience improved outcomes (20).

Pathogenic bacteria and viruses produce an enzyme called neuraminidase to avoid being trapped by mucus, one of the body’s natural defense mechanisms. Vitamin C prevents its production, making it easier for phagocytes to capture and destroy any invading organisms.

Vitamin C helps lymphocytes synthesize immunomodulatory compounds more efficiently (21). Furthermore, natural killer (NK) cells rely heavily on vitamin C for proper development and functioning – studies have demonstrated this dependency as low levels of vitamin C result in impaired cytotoxic activity that is vulnerable to hypoxia-induced impairment. At physiological doses of vitamin C levels however, NK cytotoxic activity significantly increases (22).

Vitamin C has been demonstrated to assist with the recovery of innate immunity after haploidentical stem cell transplantation (22). This may be attributed to its ability to enhance dendritic cell maturation – essential for adaptive immune responses.

Vitamin C is an essential water-soluble nutrient essential to human health. It can be obtained through diet, oral supplements and sunlight exposure; particularly oranges, berries and dark leafy greens contain high concentrations of this nutrient. For maximum bioavailability and maximum absorption it’s best when eaten alongside nuts or seeds that provide fat sources; this will bypass gastrointestinal absorption barriers (22).

2. Boosts Antioxidant Defenses

Many people take supplements claiming to boost immunity. Unfortunately, increasing immune function can backfire and cause unwanted side effects. The best way to safeguard against infections is to take preventative steps by regularly washing hands, cooking meat thoroughly and receiving recommended vaccines on time. You can also boost resilience against infection by making sure you receive enough vitamin C intake.

Vitamin C is an antioxidant water-soluble vitamin widely recognized for its protective effects against oxidative stress caused by normal metabolic processes as well as exposure to environmental toxins and pollutants. Vitamin C acts as an efficient scavenger of free radicals as well as being required for various biosynthetic and gene regulatory monooxygenase/dioxygenase enzymes; furthermore it plays a vital role in several hydroxylase reactions which form covalent bonds between endogenous electrophiles present within cell membranes; furthermore it acts as a crucial nutrient for several hydroxylase reactions that form covalent bonds between electrophiles present within cell membranes.

Vitamin C has long been acknowledged to be an effective immunomodulator, helping leukocyte migration to sites of inflammation, increasing neutrophil phagocytosis and ROS generation, while decreasing neutrophil necrosis and NETosis. Furthermore, vitamin C regulates macrophage responses to inflammation by decreasing cytokine production while simultaneously increasing antimicrobial activity.

Vitamin C boosts immune system activity by strengthening its ability to withstand oxidative stress. It does this by scavenging oxygen-derived free radicals and acting as a Michael donor – returning oxidized proteins and lipids back into their non-oxidative forms – as well as rejuvenating hydrophobic compartments with antioxidant forms of coenzyme Q10 to protect cells against free radical damage caused during mitochondrial respiration.

Studies conducted on vitamin C supplements have demonstrated their efficacy for improving ex vivo leukocyte chemotaxis and cell viability as well as decreasing TNF-a and IL-1 levels in those suffering from chronic granulomatous disease (CGD) or Chediak-Higashi syndrome with frequent infections.

Vitamin C is essential in absorbing iron from plant-based foods like beans and spinach, acting as an “ally” that enhances absorption rates while helping prevent symptoms associated with insufficient consumption (i.e. scurvy).

3. Strengthens the Immune System

The immune system of humans is an intricate network of organs, tissues, cells, proteins and antibodies which work to defend against various threats such as bacteria, viruses, fungi parasites and cancer cells. It serves as our main defense against infections; both its adaptive and innate components rely heavily on vitamin C for effective functioning.

Vitamin C plays a variety of immunomodulatory functions for both innate and adaptive immune cells, including increasing production of antiviral cytokines, decreasing proinflammatory leukocyte-derived cytokines production, supporting phagocytosis/host cell killing by phagocytes, as well as augmenting differentiation and proliferation in B and T lymphocytes due to gene regulatory effects.

Vitamin C intake has been found to enhance leukocyte function and decrease the risk of infection, especially among those with poor diets such as older adults. Its effect can be particularly dramatic.

Example of Sepsis Vitamin C Administration In an experimental model of sepsis, intravenous vitamin C administration reduced neutrophil secretions of pro-inflammatory cytokines and improved their migration ability, via attenuating oxidant generation via its gene regulatory effects, as well as decreasing several cellular signaling pathways, particularly that of pro-inflammatory transcription factor NFkB (23).

Studies conducted post-vitamin C administration indicate that improvements in neutrophil migration may be attributable to both oxidant scavenging and regeneration of important antioxidants like glutathione and vitamin E, as well as reduced polyunsaturated fatty acid oxidation in plasma membranes that leads to increased fluidity.

Vitamin C serves multiple roles within the immune system in addition to antioxidant activity, including as a cofactor for biosynthetic and gene regulatory enzymes. It scavenges free radicals in the blood and can regenerate water-soluble antioxidant coenzyme Q10. Vitamin C may also prevent pro-inflammatory cytokines such as IL-6 and TNFa from activating by quelling their biosynthesis intermediates as well as by directly inhibiting several kinases involved in its signaling pathways such as p38 mitogen-activated protein kinase’s signaling pathway.

4. Strengthens the Immune System Against Infections

Vitamin C possesses many pleiotropic benefits that come from its ability to donate electrons and serve as a cofactor for various biosynthetic and gene regulatory monooxygenase and dioxygenase enzymes that play key roles in biosynthesis and gene regulation, contributing to its immune-modulating capabilities.

Providing cells with the appropriate balance between oxidant and antioxidant defenses is integral to immunity against inflammation and cell death, but certain environmental and health conditions can alter this delicate equilibrium, leading to excess oxidant production that decreases antioxidant defenses and increases susceptibility to infections [204]. Air pollution contains numerous oxidants that damage respiratory tract lining fluid, potentially impairing immunity while increasing susceptibility [205].

Vitamin C plays a vital role in adaptive immunity as well. As well as stimulating its innate functions, vitamin C acts as an powerful water-soluble antioxidant to scavenge free radicals while replenishing important cellular and membrane antioxidants like glutathione and vitamin E. Furthermore, it accumulates in leukocytes such as neutrophils to boost their chemotaxis, phagocytosis, reactive oxygen species production that kill microorganisms, as well as their apoptosis which allows their clearance by macrophages from sites of inflammation to prevent further tissue damage.

Vitamin C plays an essential role in T- and B-lymphocyte proliferation, antibody production and resistance against various cell death stimuli. Furthermore, vitamin C modulates cytokine responses thereby attenuating excessive inflammation, hyperactivation of immune cells and increasing antiviral cytokines while simultaneously preventing cytokine-dependent autoimmune reactions.

Studies have demonstrated that high-dose intravenous vitamin C significantly reduces mortality in sepsis patients, an potentially life-threatening condition caused by failures of their circulatory, metabolic and immune systems to respond effectively to infection. The beneficial effects of vitamin C likely stem from its ability to attenuate oxidative stress while increasing phagocytosis, antibody production and natural killer cell activity while simultaneously inhibiting pro-inflammatory cytokine production in this population. Furthermore, vitamin C administration has been associated with improved recovery from ARDS which is one major cause of death among critically ill COVID-19 patients.