Vitamin C And Its Role In Immunity
L-Ascorbic Acid, As It’s Called, Isn’t Just For Winter
Vitamin C is another “star” of the immune system that many people think they know in detail: Simply take it in the winter to prevent and shorten colds.
The reality is much more complex.
As part of our series on immunity, this article explores the role Vitamin C plays in building the body’s defensive system.
A water-soluble vitamin, C is also known as L-ascorbic acid. The body can’t make this essential nutrient — it must be ingested. It is naturally present in some foods and can be added to other foods, and can also be taken as a supplement.
A diet that provides 100-200 mg of vitamin C per day should be adequate for most healthy people. Fruits and vegetables are an important source of vitamin C: A medium orange alone provides about 70 mg of the nutrient. Despite these fairly low requirements and the ubiquity of vitamin C added to foods, C deficiency is more common, as noted in various research, than we think. Earlier research, including from the U.S. Centers for Disease Control and Prevention, has indicated vitamin C to be one of the leading nutrient deficiencies in the United States. More recently, the U.S. government’s National Library of Medicine, for instance, notes the prevalence of vitamin C deficiency varies around the world, as low as about 7% in the U.S. and as high as nearly 74% in north India. Additionally, as a water-soluble vitamin, C is difficult to store. The cells that require vitamin C have mechanisms to concentrate vitamin C to the needed levels, much higher than those found in the blood.
Leading causes of vitamin C deficiency include:
- Age, is often related to diet, especially in people who are institutionalized.
- Obesity is sometimes linked to the food choices made that can lead to obesity, and with the degree of chronic inflammation and therefore consumption of vitamin C.
- Other diseases associated with chronic oxidative stress and inflammation, can also rapidly and continually deplete vitamin C stores.
- Tobacco smoke exposure, both primary and secondhand, and environmental pollution, both of which can use up vitamin C.
Vitamin C has an enormous number of functions in the immune system and in other bodily processes. Adequate amounts of C are essential in forming a particular type of chemical bond that enhances collagen synthesis and stabilization. This helps our skin maintain its all-important barrier function (and keeps it looking younger). Vitamin C enhances the proliferation and migration of fibroblasts (cells that contribute to the formation of connective tissues), which play a crucial role in repairing processes. These cells make collagen and are essential for wound healing. The antioxidant properties of vitamin C allow it to scavenge reactive oxygen species (ROS), which can damage a variety of cells, membranes, and DNA.
Phagocytes (cells that “eat’ or consume other cells and debris) are very important in the immune response. Vitamin C enhances their mobility (these cells must move to where they are needed). Vitamin C also helps phagocytes, after they have consumed cells or debris, die in a controlled fashion called apoptosis. The other type of cell death is necrotic (occurring when little blood flows to the tissue), which is uncontrolled and leads to increased inflammation. Vitamin C also aids in the differentiation and production of B and T cells, which are the foundations of the immune response. Inflammatory mediators such as cytokines and histamine are strongly influenced by vitamin C to regulate response either up or down. Finally, vitamin C also regenerates glutathione and vitamin E, both important antioxidants.
So, vitamin C isn’t just for winter anymore!
To learn more, the following articles provide a deep dive into the actions and importance of this immune powerhouse:
“Vitamin C and Immune Function”:
https://www.mdpi.com/2072-6643/9/11/1211/htm#B14-nutrients-09-01211
“Vitamin C: The Known and the Unknown and Goldilocks”:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4959991/
“The Long History of Vitamin C: From Prevention of the Common Cold to Potential Aid in the Treatment of COVID-19”:
https://www.frontiersin.org/articles/10.3389/fimmu.2020.574029/full
