The roles of micronutrients in your immune function explained

immune vitamins

Your immunes system has an elaborate army of warriors that defend you against vicious pathogens. There are specialized immune cells, physical and chemical barriers, as well as antibodies that can specifically tackle familiar pathogens. However, when it comes to brand new enemies like the novel coronavirus, COVID-19, even this intricate system can fail.coronavirus

Every stage of the immune response is heavily dependent on the presence of micronutrients, including essential vitamins and trace minerals. “Micronutrient malnutrition” is when there are deficiencies and negative consequences on the body’s ability to combat infections. Unfortunately, micronutrient deficiencies are common worldwide, including industrialized countries. So we recommend that you regularly check in your micronutrient levels with a blood test and add supplements if needed.

Elderly people, children, immunocompromised people are among the high-risk populations amid COVID-19 crisis. They are also the ones that are most susceptible to micronutrient malnutrition and week immune systems. The Harvard Medical School notes that respiratory infections and particularly pneumonia are a leading cause of death in people aged over 65, calling for preventative micronutrient supplementations.

After reviewing the latest reviews of immune-boosting micronutrients published on the prestigious journals Nutrients and Frontiers in Immunology, we recommend adequate consumption of:

  • Essential Vitamins: vitamin A, B6, B9, B12, C, D, E
  • Minerals: Zinc, Iron, Copper, Selenium
  • Probiotics

Vitamins are natural compounds that carry out important biochemical functions in the body. If their concentration is reduced due to insufficient dietary intake, there can be a number of health consequences, especially weakened immunity. Albert Szent-Gyorgyi, the Nobel laureate for Physiology and Medicine, puts it this way: “A vitamin is a substance that makes you ill if you don’t eat it.”1


Vitamin A

Vitamin A is known as an “anti-inflammation vitamin” due to its diverse roles in enhancing immune function.2 It is an integral part of the respiratory tract by promoting mucus secretion, thereby improving barrier function against infectious disease.

In addition, vitamin A is essential for the proliferation, maturation and aggregation of immune cells. Innate immune cells such as macrophages and neutrophils initiate immediate responses to an acute infection by engulfing infected cells. Vitamin A is indispensable for the production of these cells.

After the initial immune response driven by innate immunity, adaptive immune responses mediated by T cells kick in. Vitamin A continues to be an essential player by mediating T cell production, migration and its homeostasis in ongoing immune responses.

Vitamin A deficiency is closely related to infectious disease such as tuberculosis, HIV, measles and acute pneumonia. The World Health Organization (WHO) regards vitamin A deficiency as a serious public health concern for increasing the risks of mortality from infectious diseases.3 Supplementing vitamin A has demonstrated an effective therapeutic effect and is therefore recommended by the WHO.

Vitamin B complex

Vitamin B is not a single vitamin but consists of several different compounds including vitamin B1, B2, B3, B5, B6, B7, B9 and B12. Several members play important roles in boosting immune functions, namely B6, B9 and B12.

Vitamin B6 is indispensable in the differentiation and maturation of white blood cells. Even marginal deficiency has been shown to impair antibody production, and the ability to respond to infectious challenge.4 Moderate supplementation helps to restore immunity and improve the available numbers of T cells. A higher dose of supplementation has been shown to improve immune response in critically ill patients.

Vitamin B9 is also commonly known as folate, an essential supplement for pregnant women. It maintains and enhances natural killer cell activity as well as antibody production.4 Deficiency can lead to an overall impaired immune response. Folate supplementation has been shown to increase innate immunity in elderly people.

Vitamin B12 is involved in fundamental metabolism in every cell of the human body, regulating DNA synthesis and T cell replication. Vitamin B12 deficiency is known to reduce immune response during viral and bacterial infections, partly by suppressing natural killer cell activity.5 Fortunately, supplementation has been shown to restore these adverse effects and are recommended amid coronavirus crisis.4

Vitamin C

Vitamin C is an essential micronutrient that cannot be synthesized or stored by the human body. As a result, daily intake of Vitamin C from your diet or supplementation is critical.

As a cofactor for a battery of gene regulatory enzymes, Vitamin C has multifaceted functions ranging from epithelial barrier protection against pathogens to overcoming oxidative stress.6

vitamin c

Source: Vitamin C and Immune Function, Carr & Maggini, Nutrients

Vitamin C deficiency is known to result in higher susceptibility to infections. In turn, infections further exhaust vitamin C due to enhanced inflammation and metabolic requirements.

A wealth of scientific studies has supported the supplementation with vitamin C to prevent and treat respiratory and systematic infections. In a systematic review of Vitamin C and immune function, the authors concluded that: “Prophylactic prevention of infection requires dietary vitamin C intakes that provide at least adequate, if not saturating plasma levels (i.e., 100–200 mg/day), which optimize cell and tissue levels.” If someone already has an infection, significantly higher doses of Vitamin C will be required to compensate for the increased metabolic demand imposed by the inflammatory response.

Vitamin D

Vitamin D3 is the most physiologically relevant form of vitamin D. It is synthesized in the skin in a process that requires sunlight. Unfortunately, many people are deficient in vitamin D due to inadequate sun exposure and requires supplementation.forest

Vitamin D is best known for calcium and bone homeostasis. However, it also acts on both innate and adaptive immune cells, including macrophages, dendritic cells, T and B lymphocytes.7 In fact, vitamin D was used to treat infections like tuberculosis before the advent of antibiotics.

Deficiency in vitamin D can lead to increased susceptibility to infections. A study of 19,000 subjects with lower vitamin D levels showed a higher likelihood of upper respiratory tract infection.8 Since COVID-19 is also a respiratory infectious disease, it is likely that those with lower vitamin D levels may have an immune disadvantage.

Vitamin E

Vitamin E is a potent antioxidant that can protect cells from damages caused by oxidation. Notably, immune cells usually contain higher levels of vitamin E due to higher demand. There is a clear link between vitamin E deficiency and impaired immune function. Growing evidence also suggests that the current dietary guideline for vitamin E is inadequate.9

Supplementation has been shown to enhance proliferation of white blood cells, improve antibody levels and natural killer cell activity.10 A systematic review of scientific evidence supports the immunostimulatory effects of vitamin E in resisting infections such as pneumonia.


Zinc is an essential trace mineral that is required for both innate and adaptive immune functions. An estimate of 30% of the world’s population has zinc deficiency. These individuals are likely to have reduced white blood cell proliferation, antibody response, natural killer cell and macrophage cell activity.9

Multiple studies have shown that supplementation with zinc can effectively reverses these impairments. It can reduce respiratory tract infections and mortality from infectious diseases. Several high-quality clinical trails have shown that zinc supplementation can protect children and the elderly population from common colds and pneumonia.


Copper accumulates in macrophages, the cells that engulf infectious agents. Copper also has antimicrobial properties that help destroy a range of invading microorganisms.4 In addition, copper can catalyze the formation of reactive oxygen species that are toxic to pathogens.

People who are deficient in copper have abnormally low neutrophil levels and reduced ability to engulf pathogens. Moderate supplementation can effective restore its function, but excessive supplementation can also be detrimental.


Iron has many critical functions in the body, including oxygen transport and fighting pathogens. For example, neutrophils require iron to generate reactive oxygen species for killing pathogens.4 T lymphocyte proliferation and cytokine production also require iron.

Iron deficiency supresses immune responses, leading to a reduced resistance to respiratory tract infection in children. Iron supplementation can effectively improve microbial killing and clearing of the infection.

vege iron


Similar to copper and iron, selenium is also important for the proliferation of immunes cells, antibody production, and overall immunity.4 Its deficiency disrupts a number of cellular processes required for maximal immune response and increases the risk of respiratory tract infections in children. Supplementation has been shown to improve immune cell counts and enhance the immune response to viruses.


Probiotics are live microorganisms that improve gut flora and subsequently other body functions such as better immunity. The most known genera of probiotic supplements included Lactobacillus and Bifidobacterium.

Apart from improving the physical gut barrier function, probiotics can also induce anti-inflammatory cytokines, promote T and B cell functions.9 These benefits can enhance resistance against respiratory and gastrointestinal infections.

gut health


In summary, micronutrients need to be maintained at optimal levels for acute establishment as well as maintenance of immune responses. If you can, get a blood test and see if you are deficient in any micronutrient. Eat a well-balanced diet with plenty of fruits and vegetables, and supplement with immune-supportive micronutrients if needed.

Apart from these supplements, a good lifestyle is also essential. Make sure that you also:

  • Clean your hands
  • Get enough sleep
  • Manage your stress
  • Work out regularly


Online consultations available with accredited practising dietitian

To improve your immune functions, it is critical that you continue healthy habits including drinking plenty of water, good nutrition, sleep, and exercise.

We are here to provide knowledge on nutrition during this special period of time via online consultations. Please don’t hesitate to reach out for help! We are in it together.

lifestyle coronavirus

You can meet our plant-based, vegan dietitian Raymond here.


1            Mora, J. R., Iwata, M. & von Andrian, U. H. Vitamin effects on the immune system: vitamins A and D take centre stage. Nat Rev Immunol 8, 685-698, doi:10.1038/nri2378 (2008).

2            Huang, Z., Liu, Y., Qi, G., Brand, D. & Zheng, S. G. Role of Vitamin A in the Immune System. J Clin Med 7, doi:10.3390/jcm7090258 (2018).

3            Muhammad Farhan Aslam, S. M., Sidra Aslam, Jazib Ali Irfan. Vitamins: Key Role Players in Boosting Up Immune Response-A Mini Review. Vitamins & Minerals 6, doi:10.4172/2376-1318.1000153 (2017).

4            Gombart, A. F., Pierre, A. & Maggini, S. A Review of Micronutrients and the Immune System-Working in Harmony to Reduce the Risk of Infection. Nutrients 12, doi:10.3390/nu12010236 (2020).

5            Tamura, J. et al. Immunomodulation by vitamin B12: augmentation of CD8+ T lymphocytes and natural killer (NK) cell activity in vitamin B12-deficient patients by methyl-B12 treatment. Clin Exp Immunol 116, 28-32, doi:10.1046/j.1365-2249.1999.00870.x (1999).

6            Carr, A. C. & Maggini, S. Vitamin C and Immune Function. Nutrients 9, doi:10.3390/nu9111211 (2017).

7            Aranow, C. Vitamin D and the immune system. J Investig Med 59, 881-886, doi:10.2310/JIM.0b013e31821b8755 (2011).

8            Ginde, A. A., Mansbach, J. M. & Camargo, C. A., Jr. Association between serum 25-hydroxyvitamin D level and upper respiratory tract infection in the Third National Health and Nutrition Examination Survey. Arch Intern Med 169, 384-390, doi:10.1001/archinternmed.2008.560 (2009).

9            Wu, D., Lewis, E. D., Pae, M. & Meydani, S. N. Nutritional Modulation of Immune Function: Analysis of Evidence, Mechanisms, and Clinical Relevance. Front Immunol 9, 3160, doi:10.3389/fimmu.2018.03160 (2018).

10          Lee, G. Y. & Han, S. N. The Role of Vitamin E in Immunity. Nutrients 10, doi:10.3390/nu10111614 (2018).