Since the pandemic, our awareness, perhaps even fear, of viral and other infections has increased. But we have always existed in a world where we might encounter evolving variants of viral infection, with some of us seemingly more susceptible or even vulnerable than others due to our general health.
It’s the combination of exposure to bacterial, fungal or viral ‘load’ and our own ability to protect and defend ourselves that holds the key to whether we succumb. That’s the job of the immune system, our built-in ‘emergency service’, that deals with infection and helps heal the resulting damage, so we can get back to normal. So, what are the best supplement options to support our immune system to protect and defend us optimally?
How does our immune system protect us?
We’re actually under attack on a daily basis from pathogens that might want to ‘hitch a ride’ on our bodies for their own nefarious ends. Luckily, we have a highly evolved, sophisticated immune system to deal with them. So effective when working properly, we might barely notice it, but for more serious infections, it becomes painfully obvious, because is its very action creates the symptoms.
Often overlooked, a key element of defence is the quality of our barrier tissues – the skin, airways and gut. Here we physically block the infection’s access to the blood and wider body cells. Bodily fluids like mucus attempt to wash pathogens away, stomach acid kills them, and our helpful skin, gut or lung microbiome bacteria fight for supremacy. Many viruses infect via the respiratory tract, because it is an obvious entry point and they have adapted to be transmitted via the airborne route and enter cells via receptors before replicating within. The unpleasant tears, mucus, coughing, sneezing etc. are all part of the process of flushing them away before they get that far. Next up, our innate immune cells can be called into action to kill the infection or clean up the damage. This is the immune system we are born with – powerful and fast acting, but a little unsophisticated. Our adaptive immune system, with its more advanced artillery, including antibodies, might also join in especially for more complex or unusual infections. Immune function isn’t always beneficial either. The inflammatory response is powerful but damaging. If we are continually mobilising inflammation, or if it is severe, it can become self-destructive as can happen in a ‘cytokine storm’. This is the pattern we are now more than familiar with in cases of severe/long COVID.[1] As with many things, good immune function is all about balance.
Why does the immune system sometimes get compromised?
The immune system is highly influenced by nutritional status. If we are depleted in nutrients that support our barrier integrity or immune cell activity, it may be suboptimal. Key nutrients include vitamins A, C, D, zinc, and selenium.[2] Gut status has a huge impact as our immune activity is really driven from the gut. An imbalanced gut microbiome, perhaps due to the ongoing antibiotic use prescribed to tackle infections, reduces the necessary stimulation of the immune system provided by probiotic bacteria.[3] Stress levels also impact.[4] Some of us seem more genetically susceptible to infection, and suffer more from frequent or severe symptoms.[5]
How can we improve our immune system?
We can support our immune system to work better with moderate exercise, good sleep, and reducing stress. If we are infected or under the weather, we should get enough rest to allow the body to do its work. So often, when ill, we plough on but pausing and looking after ourselves in general helps us preserve the energy resource the immune system needs. The more depleted we are, the more susceptible and less likely to recover. We need to support our basic nutrition and gut health. So taking a good multivitamin and probiotic, potentially adding some extra vitamin C and vitamin D all promote the protective barriers and give our innate and adaptive immune systems what they need. If we get an infection, or if we feel especially susceptible (during winter) the above is still important of course. But we can also add in more vitamin A, C, D, and zinc. Introducing specific high dose herbs or nutrients like elderberry or lysine also help us directly fight the infection. Here’s the low-down on some of those key immunity nutrients and more, with the research behind them
Vitamin A
Vitamin A is vital for barrier integrity, helping to form a robust epithelium, improving innate and adaptive immunity, and reducing gut and respiratory infections.[6]
Vitamin C
Vitamin C increases white blood cell activity. [7] Taking it regularly when infected, reduces duration and severity of colds.[8] [9] It also improves respiratory function at levels of 400mg or more.[10] A useful protocol during infection is to ‘load’ with vitamin C taking 1g an hour for several hours (and being cautious not to hit ‘bowel tolerance’). This is best achieved with a vitamin C powder mixed into water.
Vitamin D
Vitamin D supports a balanced immune response, both improving antiviral and antibacterial response, but also modulating excess inflammation by reducing proinflammatory cytokines. Deficiency is linked to increased susceptibility to COVID, and respiratory infections.[11] [12] We can probably all benefit from at least 2000iu a day, potentially more in winter, especially if deficient.
Zinc
Zinc is central to immune function, supporting the health of the barrier membranes and increasing immune cell replication, including natural killer cells, enhancing B and T cell function. [13] Supplementing zinc increases immunity in children[14] and the elderly.[15]
Elderberry
Elderberry – nature’s natural antiviral blunts the ‘spike proteins’ viruses use to enter our cells and start to replicate. It shortens duration and reduces severity of cold and flu. The polyphenols also act as antioxidants, helping protect cells and modulate cytokine activity (TNF-α, IFN-γ and IL-2) inflammation so it improves immunity with no risk of overstimulation.[16] [17]
Lysine
Lysine – inhibits viral replication, aids antibody production and tissue repair.[18]
Beta Glucans
Beta Glucans stimulate immunity and can reduce symptomatic common cold infections by 25 %.[19]
Thyme
Thyme supports lung health through a blend of anti-inflammatory, antimicrobial, and expectorant effects, helping to reduce mucus, clear airways and enhance respiratory function. [20]
NAC
N-Acetyl Cysteine can thin and clear mucus and may support a range of chronic respiratory conditions such as COPD, asthma, fibrosis, acute lung injury, ARDS, and COVID.[21]
Medicinal mushrooms
Cordyceps mushroom enhances overall lung health, while also reducing inflammation.[22] [23]<//sup> The triterpenes in Reishi mushroom reduces inflammation and promotes natural killer cell activity and IFN-γ, combatting viral infections such as flu. [24]
Probiotics
Probiotics can help promote balance in gut, skin and lung microbiomes. Certain probiotics, especially L rhamnosus GG, have proved effective at improving immune function to prevent and reduce symptoms and duration of respiratory infections.[25]
Summary
The immune system is our best friend, especially during winter months, when infection tends to increase. It often works effectively in the background to protect us, but also uses a lot of physical resource, so can become depleted. There’s much we can do to help and feeding it the right nutrients and looking after ourselves in general to allow rest and recovery, can make a big difference in our quest for optimum ‘self-defence’.
For further information on specific lung support, read: Seeking inspiration – Looking after the lungs.
References
[1] Ghaffarpour, S. et al. (2025). Cytokine profiles dynamics in COVID-19 patients: a longitudinal analysis of disease severity and outcomes. Scientific reports, 15(1), 14209.
[2] Morales, F., Montserrat-de la Paz, S., Leon, M. J., & Rivero-Pino, F. (2023). Effects of Malnutrition on the Immune System and Infection and the Role of Nutritional Strategies Regarding Improvements in Children’s Health Status: A Literature Review. Nutrients, 16(1), 1. https://doi.org/10.3390/nu16010001
[3] Mazziotta, C., Tognon, M., Martini, F., Torreggiani, E., & Rotondo, J. C. (2023). Probiotics Mechanism of Action on Immune Cells and Beneficial Effects on Human Health. Cells, 12(1), 184. https://doi.org/10.3390/cells12010184
[4] Segerstrom, SC. & Miller, GE. (2004) Psychological stress and the human immune system: a meta-analytic study of 30 years of inquiry. Psychol Bull. 130 (4): 601-630.
[5] Conti, F. et al. (2025) Unravelling the Genetic Predisposition on Respiratory Infections: From Single Nucleotide Polymorphisms to Inborn Errors of Immunity, Interdisciplinary Perspectives on Infectious Diseases. 1081820, 19
[6] Huang, Z et al. (2018). Role of Vitamin A in the Immune System. Journal of clinical medicine, 7(9), 258.
[7] Hu, B. et al. (2025) Dietary Vitamin C Intake Affects Lung Function Through White Blood Cell. Food Science & Nutrition. 13(5):e70299-e70299.
[8] Hemilä, H. & Chalker, E. (2013). Vitamin C for preventing and treating the common cold. The Cochrane database of systematic reviews, 2013(1), CD000980.
[9] Carr, A. C., & Maggini, S. (2017). Vitamin C and Immune Function. Nutrients, 9(11), 1211.
[10] Lei, T. et al. (2022) Efficacy of Vitamin C Supplementation on Chronic Obstructive Pulmonary Disease (COPD): A Systematic Review and Meta-Analysis. International Journal of Chronic Obstructive Pulmonary Disease. Volume 17:2201-2216.
[11] Gayan‐Ramirez, G & Janssens, W. (2021) Vitamin D actions: The lung is a major target for vitamin D, FGF23 and klotho. JBMR Plus.
[12] Gaudet, M. et al. (2022) Recent advances in vitamin D implications in chronic respiratory diseases. Respiratory Research. 23(1).
[13] Wessels, I., Maywald, M., & Rink, L. (2017). Zinc as a Gatekeeper of Immune Function. Nutrients, 9(12), 1286. https://doi.org/10.3390/nu9121286
[14] Cunningham-Rundles, S. et al. (2005). Mechanisms of nutrient modulation of the immune response. The Journal of allergy and clinical immunology, 115(6), 1119–1129. https://doi.org/10.1016/j.jaci.2005.04.036
[15] Mocchegiani, E., Muzzioli, M., & Giacconi, R. (2000). Zinc and immunoresistance to infection in aging: new biological tools. Trends in pharmacological sciences, 21(6), 205–208.
[16] Hawkins, J. et al. (2019). Black elderberry (Sambucus nigra) supplementation effectively treats upper respiratory symptoms: A meta-analysis of randomized, controlled clinical trials. Complementary therapies in medicine, 42, 361–365.
[17] Zakay-Rones, Z. et al. (2004). Randomized study of the efficacy and safety of oral elderberry extract in the treatment of influenza A and B virus infections. The Journal of international medical research, 32(2), 132–140.
[18] Pedrazini, M. C., da Silva, M. H., & Groppo, F. C. (2022). L-lysine: Its antagonism with L-arginine in controlling viral infection. Narrative literature review. British journal of clinical pharmacology, 88(11), 4708–4723.
[19] Auinger, A. et al (2013). Yeast (1,3)-(1,6)-beta-glucan helps to maintain the body’s defence against pathogens: a double-blind, randomized, placebo-controlled, multicentric study in healthy subjects. European journal of nutrition, 52(8), 1913–1918.
[20] Oliviero, M et al. (2016) Evaluations of thyme extract effects in human normal bronchial and tracheal epithelial cell lines and in human lung cancer cell line. Chemico-Biological Interactions. 2016;256:125-133.
[21] Mokra D, Mokry J, Barosova R, Hanusrichterova J. Advances in the Use of N-Acetylcysteine in Chronic Respiratory Diseases. Antioxidants. 2023;12(9):1713.
[22] Yu, X. et al. 2019) Effectiveness and Safety of Oral Cordyceps sinensis on Stable COPD of GOLD Stages 2–3: Systematic Review and Meta-Analysis. Evidence-Based Complementary and Alternative Medicine. 2019:1-12.
[23] MU, Wie. et al. (2013) Cordyceps Sinensis for Chronic Obstructive Pulmonary Diseases: A Systematic Review. Chinese Journal of Evidence-Based Medicine, 2013, 13(11): 1373-1381.
[24] Plosca, MP. et al. (2025) Ganoderma lucidum—From Ancient Remedies to Modern Applications: Chemistry, Benefits, and Safety. Antioxidants. 14(5):513.
[25] Zuhair, M. N. et al. (2025). Role of Lacticaseibacillus rhamnosus GG in the Management of Respiratory Diseases: A Systematic Review and Meta-Analysis. Preventive nutrition and food science, 30(3), 222–229.
All of our blogs are written by our team of expert Nutritional Therapists. If you have questions regarding the topics that have been raised, or any other health matters, please do contact them using the details below:
nutrition@cytoplan.co.uk
01684 310099
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Last updated on 10th December 2025 by cytoffice
