The immune system protects us from infections and foreign agents. It is made up of a very complex network of cells and substances which, with different activities, are distributed in all tissues.
Vitamin C, called ascorbic acid, is a water-soluble carbohydrate. It cannot be synthesised by the human body and comes from fruit and vegetables. Its requirements are higher in people over 60, pregnant women and smokers. Athletes need an additional 200 milligrams a day to maintain the proper functioning of the immune system during and after intense exercise.
Action on the immune system
Vitamin C can stimulate the function of neutrophils, a type of white blood cell that repairs injured tissues and fights infection. It also increases the action of interferon, a molecule that blocks viruses from entering cells. Supplements containing vitamin C appear to improve the function of some immune processes. These include the proliferation of T-lymphocytes, the production of cytokines and immunoglobulins, and the effectiveness of natural killer or NK cells. Their effect on the intensity and duration of colds is controversial. However, there is evidence that may support high doses of vitamin C for this purpose. In the work of Gorton and co-workers (1) it was recorded that cold symptoms were reduced by 85 %. As for the effect of vitamin C on COVID-19, this is also a controversial point. However, a study published in the Biorxiv repository (2) in 2021 seems to indicate that this substance inhibits the proteases of the virus, the molecules essential for its replication. Furthermore, in older people, the results of a paper published in Experimental Gerontology (3) support the use of vitamin C supplements of 500 milligrams per day in people over 70 years of age. Immune system function improved significantly to the levels of young adults.
Collagen’s relationship with vitamin C
Vitamin C is involved in the synthesis of collagen, the body’s main structural protein. It is an essential part of connective tissue, which supports organs such as blood vessels, teeth, gums, skin and bones, providing them with strength. It is also involved in the formation of the epithelial barrier, providing a firm bond between the cells that make up the barrier. The relationship between collagen and vitamin C is very close. It functions as a reducing agent, donating electrons to enable eight enzymes to function properly. These are involved in the process of hydroxylation of the amino acids proline and lysine, which are essential in the synthesis of the fibres of this protein.
Role as antioxidant
One of the main functions of vitamin C is antioxidant, since oxidative agents alter the redox balance in tissues. One cause is free radicals or FR; they are very unstable and are generated by external agents such as ultraviolet rays, pollution, ozone and cigarette smoke. The conversion of food to energy and inflammatory processes also produce FR and ROS, or reactive oxygen species. These two types of electrically charged molecules damage DNA, cell membranes, and structural proteins (elastin and collagen), thereby inducing tissue aging. Vitamin C could protect cells, since it intervenes in the processes that cause oxidative damage (4) and neutralizes them by giving up electrons to RLs and ROS. Other possible beneficial effects of vitamin C are the following: it contributes to maintaining normal energy metabolism, the functioning of the nervous system, reduces fatigue and improves iron absorption.
An excellent antioxidant combination
At the beginning of this article, it was mentioned that some minerals can enhance the effect of ascorbic acid. A very effective anti-ox combination is the one obtained with vitamin C together with zinc and selenium. Food supplements in many cases contain vitamin C from natural sources, such as rose hips or the fruit of the wild rose, called Rosa canina.
Zinc and its properties
Foods with zinc are beneficial for health, since this mineral is found in all the cells of our body and is involved in various processes. It is convenient to know what zinc is for, because among other functions it promotes the proper functioning of the immune system. Supplements that contain it prevent colds and relieve symptoms (5) when they occur. This mineral participates in the processes of cell division and differentiation in healing. In turn, it is related to bones, nails and skin, as it activates their growth. Additionally, it maintains cognitive functions, is involved in the metabolism of macronutrients and in protein synthesis.
Selenium and the immune system
Like zinc, this is a trace element that is needed by the body in small amounts. We get selenium from foods like shellfish, meat, eggs, and cereals. Selenium is essential for the adequate response of the immune system, since its deficiency alters the production of immunoglobulins IgM and IgG (6) and hinders the motility of neutrophils. It seems to be essential in thyroid function and in the regulation of redox mechanisms. Likewise, it protects cells from oxidative damage, since it is a cofactor of enzymes that intervene in these processes. The immune system and vitamin C have a link that is enhanced by the presence of selenium and zinc in food supplements. This combination has a synergistic effect that is highly beneficial for a wide range of functions in our body.
- Clay Gorton, DC, Kelly Jarvis, DC. The effectiveness of vitamin C in preventing and relieving the symptoms of virus-induced respiratory infections. Journal of Manipulative and Physiological Terapeutics Volume 22, Issue 8, P530-533,1999.
- Narsingh Malla, S. Pandey. Vitamin C inhibits SARS coronavirus-2 main protease essential for viral replication. BiorXiv, 2021.05.02.442358.
- De la Fuentea, C. Sánchez. Vitamin C and vitamin C plus E improve the immune function in the elderly. Experimental Gerontology, Volume 142, December 2020, 111118.
- Pullar JM, Carr AC. The Roles of Vitamin C in Skin Health. Nutrients. 2017;9(8):866. doi: 10.3390/ nu9080866
- Douglas, R.M. & H. Hemila. 2005. Vitamin C for preventing and treating the common cold. PLOS Medicine 2: e168
- Schomburg L. Selenium, selenoproteins and the thyroid gland: interactions in health and disease. Nat Rev Endocrinol. 2012;8(3):160-171