Immune support and Respiratory Illnesses

Immune support and Respiratory Illnesses

Cyrus Kuhzarani R.Phm.

12 Nov 2021

Immune support and Respiratory Illnesses

With the advent of Covid-19 there has been an increased interest in looking at supplementation to help with respiratory illness. 

Vitamin C is critical to the support of the immune system.  It helps to stimulate white blood cells such as neutrophils and has been shown to stimulate the clearance of infection.  Vitamin C also helps to enhance the adaptive immunity by stimulating the proliferation of B cells and T cells and can both prevent and treat respiratory and systemic infections.
Prophylactic prevention of infection requires 100-200 mg/day of Vitamin C to optimize cell and tissue levels.1

One study looked at the effects of Vitamin C given to elderly patients admitted to the hospital with acute respiratory infections such as bronchitis and bronchopneumonia. 
Patients given just 200 mg of Vitamin C showed improvement of major symptoms as compared to the placebo group.2
Some smaller studies have shown that the common cold was found to decrease by 30% in those taking Vitamin C.3

One study looking at Covid-19 treatments provided evidence that oral Vitamin C at a dosing of 2-8 g/day could reduce the incidence of respiratory infection.4 

Another meta-analysis showed a reduced length in ICU patients with respiratory infections and shortened the duration of mechanical ventilation suggesting Vitamin C should be considered for complications of Covid-19.5 

Zinc also appears to be an important modulator in the production of immune cells ensuring the proper action of white blood cells.  A study in those with upper respiratory infections showed that those that supplemented with zinc gluconate, 15 mg/day, experienced more symptom-free episodes of upper respiratory infection than those in the placebo group.6 Another study showed that doses of 75mg/day reduced the duration of symptoms up to 2 days in viral respiratory infections.7 

Zinc has been shown to slow down the work of RNA polymerase (an enzyme that synthesizes viral RNA molecules such as coronaviruses) and suppresses viral spread in the body.8

Zinc decreases the activity of the angiotensin-converting enzyme 2 (ACE2) which is known to be a receptor for SARS-Cov-2.  Zinc produces anti-inflammatory activity by modulating T-cell production and limits cytokine storms in the body.9 Zinc has also been shown to improve muco-ciliary clearance in the lungs and can prevent ventilator-induced lung injury.10

Vitamin D3 has also been studied in relation to respiratory illness.  Vitamin D3 has been found to be capable of inhibiting the pulmonary inflammatory response and enhancing the innate immune response against respiratory pathogens.11

Vitamin D3 has been shown to increase the secretion of an antimicrobial peptide, cathelicidin, which has been found to alter T-cell activation and the host responses against infection.12 One study also showed that 3000-4000 IU of Vitamin D3 reduced acute respiratory infections by 40%.13 During the Covid-19 pandemic Vitamin D3 deficiency has been associated with a higher risk of mortality.14 

N-Acetyl-Cysteine (NAC) is a sulfur-containing precursor of the amino acid L-cysteine and the antioxidant glutathione. 

As an antioxidant itself, NAC protects cells from damage caused by the excessive oxidative stress that results from inflammatory states, chronic disease, prolonged strenuous exercise, pollution exposure and generalized stress. 15,16
NAC does all this with the help of Selenomethionine, by way of replenishing the body’s intracellular antioxidant, glutathione, via the glutathione redox system. 

NAC also has the ability to reduce the viscosity of mucus and stimulates the clearing of mucus from the airways. This makes NAC a valuable component of any respiratory symptom-management program where congestion occurs. 17

Since the pandemic interest in the variety of natural supplementats aiming to treat upper respiratory infection has risen significantly. 
Vitamin C, Vitamin D3, Zinc, NAC and Selenomethionine should be considered as an adjunctive treatment of Covid-19 or any upper respiratory infections.



  1. Carr, Anitra C et al. 2017. “Vitamin C and Immune Function,” Nutrients 9(11) (November), (accessed September 15, 2021).
  2. Hunt, C, 1994. “The Clinical Effects of Vitamin C supplementation in elderly hospitalized patients with acute respiratory infections.” 64. Abstract in International Journal for Vitamin and Nutrition Research.
  3. Hemila, H, 1999. “Vitamin C and acute respiratory infections.” 3. Abstract in The International Journal of Tuberculosis and Lung Disease.
  4. Holford, P, 2020. “Vitamin C – An Adjunctive Therapy for Respiratory Infections, Sepsis, and Covid-19.” 12. Abstract in Nutrients. 12.
  5. Hemila, H, 2021. “Vitamin C and Covid-19.” 2021. 18. Abstract in Frontiers in Medicine. 7.
  6. Verveka, D, 2009. “Use of zinc supplements to reduce upper respiratory infections in United States Air Force Academy cadets.” 15. Abstract in Complementary Therapies in Clinical Practice.
  7. Read, S, 2019. “The Role of Zinc in Antiviral Immunity.” 10. Abstract in Advances in Nutrition.
  8. Skalny, A, 2020. “Zinc and respiratory tract infections: Perspectives for Covid-19.” 46. Abstract in International Journal of Molecular Medicine.
  9. Anatoly, S et al. 2020. “Zinc and respiratory tract infections: Perspectives for Covid-19,” International Journal of Molecular Medicine 46 (1) (April), (accessed September 20, 2021).
  10. Arentz, S et al. 2020. “Zinc for prevention and treatment of SARS-CoV-2 and other acute viral respiratory infections: a rapid review.” Advanced Integrative Medicine 7(4) (December), (accessed September 21, 2021).
  11. Hughes, D et al. 2009. “Vitamin D and respiratory health.” Clinical Experimental Immunology 158 (1) (October), (accessed September 20, 2021).
  12. Hansdottir, S et al. 2011. “Vitamin D effects on lung immunity and respiratory diseases.” 86. Abstract in Vitamins and Hormones.
  13. Peckel, Linda 2016. High-Dose Vitamin D Reduces Acute Respiratory Infection in Elderly. Infectious Disease Advisor, December 11. (accessed September 22, 2021).
  14. Vaghari-Tabari, 2021. “Vitamin D and respiratory viral infections.” 2. Abstract in Critical Reviews in Food Science and Nutrition.
  15. Dekhuijzen PN, van Beurden WJ. The role for N-acetylcysteine in the management of COPD. Int J Chron Obstruct Pulmon Dis. 2006;1(2):99-106.
  16. Dodd S, Dean O, Copolov DL, Malhi GS, Berk M. N-acetylcysteine for antioxidant therapy: pharmacology and clinical utility. Expert Opin Biol Ther. 2008;8(12):1955-1962.
  17. Conrad C, Lymp J, Thompson V, et al. Long-term treatment with oral N-acetylcysteine: affects lung function but not sputum inflammation in cystic fibrosis subjects. A phase II randomized placebo-controlled trial. J Cyst Fibros. 2015;14(2):219-227.

Blog Post Image

The Melatonin-Sleep-Cancer Connection


Blog Post Image

Ramifications of pH Imbalance on Mental Health


Replenish Your Body

See how you can benefit from our unique line of products.

Find a Store

Find our products at your nearest PLV retailer.