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The immune system protects the host by forming barriers against pathogenic organisms, including bacteria, viruses, fungi, and parasites. But what are the best vitamins for immune system support?
An immune response is achieved by a collection of white blood cell types, such as macrophages, neutrophils, natural killer cells, and B and T lymphocytes. B cells produce antigen-specific antibodies, which are proteins involved in the identification and removal of foreign substances in the body; antibodies are crucial in the creation of vaccines to provide lifelong immune protection.
Immune function is both constant and indispensable but increases in the presence of infection. This heightened activity is associated with a higher metabolic rate, which utilises more energy sources derived from the diet. A defective immune system can arise due to increased age or obesity and can lead to infection, autoimmunity, cancer, and heart disease.
Vitamins and Minerals
There are a number of nutrients found in dietary sources that support the human immune system and lowers the risk of infections. These include vitamins (A, B6, B12, folate, C, D, and E) and trace elements, such as zinc, copper, selenium, and iron. All these micronutrients are recognised by the European Food Safety Authority to be involved in the ‘maintenance of functions of the immune system’. Excluding vitamin C and iron, these nutrients are necessary for antibody production, emphasising the key relationship between nutrition and immunity.
What are the best vitamins for immune system support?
Vitamin A and its metabolites are vital for normal epithelial differentiation and the development and function of immune cells. Known as an anti-inflammation vitamin, vitamin A influences neutrophil maturation and natural killer cell activity. Vitamin A deficiency is linked to abnormal modifications in immune responses, impaired mechanical barrier function and enhanced susceptibility to infection. Vitamin A appears to have a therapeutic effect in the treatment of numerous infectious diseases (including tuberculosis, measles, and acute pneumonia); this highlights the potential use of supplementation to maintain a healthy vitamin A status and thereby prevent and cure severe symptoms of COVID-19. Dietary sources: Milk and cheese, eggs, oily fish, orange fruits (mango, peaches, apricots)
B-group vitamins – specifically B6, B9 (folate) and B12 – regulate immune cells in the intestines involved in the gut barrier function. Vitamin B6 deficiency affects the thymus and spleen and reduces numbers of T lymphocytes in the blood. Vitamin B12 deficiency exacerbates neutrophil function and it has been suggested that supplements of this vitamin would be particularly useful for vegans. A deficiency in folate negatively impacts on cell-mediated immunity, which is the targeting of pathogens by T cells; folic acid supplements are highly recommended to pregnant women to support the metabolism of vitamins and amino acids. Dietary sources: Fish, meat, eggs, yeast extract
Vitamin C is crucial for the maintenance of epithelial integrity and the function of T lymphocytes and natural killer cells. Vitamin C deficiency increases susceptibility to severe respiratory infections including pneumonia; however, supplementation with this vitamin is associated with a significant decrease in the incidence of pneumonia and severity of upper respiratory tract infections, for example, the common cold. Dietary sources: Oranges and orange juice, red and green peppers, strawberries, potatoes
Vitamin D receptors are present in most immune cells, implying that it has essential immunoregulatory properties. Vitamin D improves the integrity of epithelial cells and has a multitude of cellular immune functions. In addition to regular exposure to sunlight, vitamin D can be obtained through the diet and Vitamin D3 tablets. Daily vitamin D supplements have been found to reduce the risk of upper respiratory tract infections, such as pneumonia and influenza. Dietary sources: Oily fish, liver, eggs, fortified foods (spreads and some breakfast cereals)
Vitamin E is a potent antioxidant and is involved in the regulation of neutrophil and natural killer cell activity, in addition to antibody production after vaccination, and enhanced resistance to infections. Vitamin E supplementation seems to have a particular benefit for the elderly, although studies have found varying results on its effectiveness in treating and preventing infectious diseases. Dietary sources: Many vegetable oils, nuts, seeds
Zinc is involved in the maintenance of T and B lymphocyte levels and may have a chief role in antiviral immunity since it inhibits the RNA polymerase enzyme needed by RNA viruses, such as coronaviruses, to replicate. Oral zinc supplements may reduce the duration of a typical common cold and decrease mortality in adults with severe pneumonia. Dietary sources: Shellfish, meat, cheese, some grains and seeds
Copper supports the development of immune cells, such as neutrophils, macrophages, and natural killer cells. Copper has antimicrobial and antiviral properties so supplements of this micronutrient may boost immunity. Dietary sources: Shellfish, nuts, liver, some vegetables
Selenium maintains the function of T and B lymphocytes and reduces the risk of viral infection. It has been demonstrated that selenium supplements have improved immune function in humans, including the elderly population. Dietary sources: Fish, shellfish, meat, brazil nuts
Iron deficiency can result in deterioration of the thymus, thereby reducing T lymphocyte proliferation and increasing susceptibility to infection. Conversely, it is important to prevent excess iron in the diet as it impairs immune function, causes inflammation and may provide favourable conditions for microorganisms to grow. Dietary sources: Meat, liver, beans, dark green leafy vegetables (spinach, kale)
A healthy immune system requires a conscious effort to live a healthy lifestyle; it is important to maintain healthy concentrations of these vitamins and minerals in the body through dietary intake. However, people with deficiencies in certain vitamins can improve their immune system with vitamin supplements that will suit their unique requirements. Consult your doctor before taking vitamin or mineral supplements.
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1. Calder, P.C. (2020). Nutrition, immunity and Covid-19. BMJ Nutrition, Prevention & Health.
2. Huang, Z., et al. (2018). Role of vitamin A in the immune system. Journal of Clinical Medicine, 7(9), p.258.
3. Jayawardena, R., et al. (2020). Enhancing immunity in viral infections, with special emphasis on COVID-19: A review. Diabetes & Metabolic Syndrome: Clinical Research & Reviews, 14, pp.367-82.
4. Adhikari, P.M., et al. (2016). Effect of vitamin B12 and folic acid supplementation on neuropsychiatric symptoms and immune response in HIV-positive patients. Journal of Neurosciences in Rural Practice, 7(03), pp.362-67.
5. Lee, G.Y. and Han, S.N. (2018). The role of vitamin E in immunity. Nutrients, 10(11), p.1614.
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