Vitamin C and Immune Function

Vitamin C (ascorbic acid) is a six-carbon lactone which is synthesized from glucose by many animals. Vitamin C is synthesized in the liver in some mammals and in the kidney in birds and reptiles. However, several species - including humans, non-human primates, and guinea pigs - are unable to synthesize vitamin C. 

Vitamin C is an ideal marker for overall health; it is the first nutrient to be depleted in alcoholics, smokers, and obese individuals. 

An Immunostimulant

Vitamin C is crucial for both innate and adaptive immunity. White blood cells, such as neutrophils and monocytes, actively accumulate vitamin C against a concentration gradient, resulting in values that are 50- to 100-fold higher than plasma concentrations. 

Vitamin C supports the production and function of various white blood cells, including lymphocytes and phagocytes. These cells are involved in identifying, attacking, and neutralizing harmful microorganisms such as bacteria and viruses. Vitamin C helps these cells to function more effectively and efficiently, improving the body’s response to infections.

Vitamin C shields immune cells from oxidative stress. It strengthens skin barrier and promotes collagen synthesis and wound healing. It balances cytokine production and reduces excessive inflammation. It enhances antimicrobial activity. It reduces duration/severity of colds, aids in severe infections like pneumonia and sepsis.  

Collagen Synthesis

Vitamin C is essential for collagen synthesis, which is critical for the structural integrity of the skin and mucosal barriers. These barriers are the first line of defense against pathogens. A strong, healthy skin and mucous membranes are better equipped to block pathogens from entering the body.

Iron Absorption

Vitamin C enhances the absorption of non-heme iron from plant-based foods, helping prevent iron deficiency anemia. Iron deficiency anemia impacts the immune system significantly, as iron is essential for the development and function of immune cells.

Wound Healing

Vitamin C aids in the repair of tissues and the healing of wounds due to its role in collagen formation.

Reduction of Inflammation

Vitamin C can help reduce inflammation, which is often a consequence of infections. By modulating the immune system, it may reduce excessive inflammation, preventing it from becoming harmful while still allowing the body to fight infections effectively.

Skin's Immunity

Vitamin C plays a vital role in boosting the skin's immunity, acting as a shield against various environmental and microbial threats. Vitamin C promotes the production of ceramides and lipids, which fortify the skin barrier and reduce the risk of infections and irritants penetrating the skin.  

As a powerful antioxidant, Vitamin C neutralizes free radicals generated by UV rays, pollution, and other stressors. This protection minimizes oxidative stress, which can compromise the skin's natural defenses.  

By stimulating collagen production and supporting tissue repair, vitamin C accelerates the healing of cuts, scrapes, and other skin injuries, reducing the risk of infections.  

Vitamin C supports the activity of Langerhans cells in the skin, which are essential for identifying pathogens and coordinating an immune response. It helps to modulate the immune response, decreasing excessive inflammation caused by irritants or skin conditions like eczema or psoriasis.  

Clues to the role of vitamin C in the skin come from the symptoms of the vitamin C deficiency disease scurvy, which is characterized by bleeding gums, bruising, and impaired wound healing. 

Vitamin C enhances the production of antimicrobial peptides in the skin, which help to fight off bacteria, viruses, and other harmful microbes.

The elevated antioxidant status of the skin following vitamin C supplementation could potentially protect against oxidative stress induced by environmental pollutants. 

Antimicrobial Peptides

Antimicrobial peptides (AMPs) are small proteins that play a crucial role in the body's innate immune defense by neutralizing pathogens such as bacteria, viruses, and fungi. Vitamin C has been found to stimulate the production and activity of certain AMPs, enhancing the immune system's ability to combat infections. 

Vitamin C upregulates the expression of key antimicrobial peptides such as cathelicidins and defensins, which are essential for pathogen neutralization. It supports gene expression pathways involved in the synthesis of AMPs, particularly through its antioxidant and signaling roles.  

Vitamin C enhances the activity of AMPs in epithelial cells, such as those in the skin and respiratory tract, improving the barrier's ability to resist microbial invasion. AMPs stimulated by vitamin C help protect against respiratory pathogens, contributing to defenses in the lungs and sinuses.  

By boosting AMP levels, vitamin C amplifies the innate immune response, helping macrophages and neutrophils eliminate pathogens more effectively. It reduces inflammation caused by infections, allowing AMPs to function more efficiently in a less hostile environment.  

Vitamin C’s promotion of AMP activity is particularly beneficial in wound sites, preventing infection and accelerating recovery.  

A Powerful Antioxidant

Vitamin C is a powerful antioxidant, helping to protect immune cells from oxidative stress and damage caused by free radicals. This protection is essential for maintaining the health and function of immune cells, including white blood cells, which are key to the body’s defense against pathogens. This action helps prevent premature aging and reduces the risk of chronic diseases like cancer, heart disease, and neurodegenerative disorders. It also regenerates other antioxidants like vitamin E, enhancing the body's defense system.

Cancer Prevention

Vitamin C plays a complex role in cancer prevention and treatment, with potential benefits attributed to its antioxidant and pro-oxidant properties. Vitamin C helps protect cells from oxidative damage caused by free radicals, which can lead to cancer. 

Its preventive role includes neutralizing free radicals and reducing oxidative stress that contributes to DNA damage and mutations.

Vitamin C supports the immune system in identifying and destroying cancerous cells and through its anti-Inflammatory effects it decreases chronic inflammation which is a risk factor for cancer development.

Foods High in Vitamin C

Foods rich in vitamin C are guava, kiwi, broccoli, citrus fruits, bell peppers, papayas, strawberries, lemon, and tomatoes. Other good sources include dark leafy greens, cantaloupe, mango, watermelon, cauliflower, cabbage, raspberries, blueberries, and pineapples.