We all know that vitamin C is good for us, and that citrus is a good food to indulge when we’re ill. But a paper titled Vitamin C and Immune Function reviewed over two hundred fifty scientific papers to demonstrate just that.
There are multiple lines of defense in the human immune system. Vitamin C strengthens and sharpens many of them, from the outer physical skin boundary to the activity of B and T lymphocytes.
The skin is the first line of defense, so its health is of immunological interest. Vitamin C can easily donate electrons, making it a powerful antioxidant and thus protective on the skin. It is also a cofactor in reactions for enzymes that strengthen and stabilize collagen; collagen enables skin elasticity and plenty of it around means any open wounds on the skin can heal faster.
A neutrophil is one of the first responders to a pathogen in the human body, and it rapidly accumulates vitamin C in high concentrations. Within neutrophils – a type of phagocyte – vitamin C has many roles.
The first is in chemotaxis. Neutrophils sense molecules emitted by the pathogen and move towards it, and studies have shown that adequate vitamin C enhances this chemotactic ability. It has been suggested that vitamin C stabilizes microtubules, and microtubule assembly enables cell travel.
Once the neutrophil reaches the pathogen, it engulfs it via phagocytosis. Once swallowed by the neutrophil, the pathogen is destroyed with ROS – reactive oxygen species, another strategy that relies on vitamin C’s oxidative power to work. According to at least one study, decreased ability to ‘phagocytose’ or eat pathogens is associated with increased risk for patient mortality. And what strengthens this phagocytosis and oxidative pathogen slaughter? Vitamin C.
After the neutrophil has completed its search-and-destroy mission, it dies. Caspases are enzymes that mark the cell for death, and they are keen on items inactivated by ROS. In other words, vitamin C’s activation of neutrophils also streamlines apoptosis. Neutrophils that don’t self-destruct undergo necrosis instead, which is essentially cell rot. The insides of neutrophils were toxic to the pathogen it consumed will be toxic as well to human tissue.
B-lymphocytes and T-lymphocytes accumulate vitamin C as well. These cells are your heroes for adaptive immunity, producing antibodies to prevent infection by the same pathogen ever again. It is less well known how exactly vitamin C helps lymphocytes out, but studies do associate vitamin C supplementation with enhanced lymphocyte activity.
Inflammation is your body’s healthy response to an infection, but sustained inflammation will result in negative infects. Thus vitamin C’s anti-inflammatory effects are a final boost to your health as you fight off an infection or infectious disease.
There are many genes involved in the inflammatory response which upregulate production of key proteins and other molecules. Vitamin C can suppress inflammatory molecule production and upregulate anti-inflammatory molecule production. For example, it acts as an antihistamine; histamine is a pro-inflammatory molecule.
Disease & Prevention
One of the ways we can learn about the importance of vitamin C is by studying those who lack it. Scurvy is a disease caused by chronic vitamin C malnutrition; victims of this disease are at a higher risk for chronic infection, have more respiratory infections, have impaired immunity, and take longer to heal open wounds on the skin.
Why are respiratory infections more common with vitamin C deficiencies? Skin is a great barrier for much of the body, but we can breathe in a lot of gunk. Air pollution, air-borne pathogens, tobacco smoke, and other compounds can cause oxidative damage inside the lungs, and we’ve already seen that vitamin C works as a great antioxidant, protecting lung tissue from such exposure.
The most common cause of death in scurvy patients is respiratory infection. Once infected, the immune response demands higher vitamin C needs, making the original deficiency even more acute. Thus, consuming vitamin C can both prevent infection and aid in the recovery process. This is corroborated by studies showing reduced hospital stay for patients given vitamin C supplements.
Always take your vitamins. 🙂 Stay healthy all, and eat well!
This is not medical advice. 🙂 It is an amateur’s attempt to summarize a review paper.