Author: Amna Paracha, PharmD Candidate, Class of 2021 University of Maryland Eastern Shore School of Pharmacy and Health Professions

As COVID-19 continues to spread, many people are interested in boosting their immunity against the virus. The Center for Disease Control (CDC) stresses that dietary supplements are not meant to treat or prevent COVID-19 however can affect out immune system’s ability to fight infections and reduce inflammation.1 Further, lifestyle modifications can be taken to strengthen our internal defense system.

According to Harvard Health, the first step to strengthen the immune system is to engage in a healthy lifestyle.2 Eating a diet filled with fruits and vegetables, limiting the amount of alcohol consumption, and quitting smoking are the first steps to take. Chronic stress is associated with elevated cortisol levels which can cause immune dysregulation that varies in severity.3 Psychological stress can be minimized through meditation which has been shown to reduce anxiety, lower blood pressure, and lower heart rate.4 Ensuring a sufficient night of sleep reduces stress and influences the immune system in a positive manner. A 2020 systemic review looked at results of the Wisconsin Upper Respiratory Symptom Survey which showed exercise reduced the severity of acute respiratory infection and the number of days patients experienced symptoms however no significant changes in laboratory parameters and quality of life symptoms were seen.5 Regularly engaging in moderate intensity exercise should be encouraged to help maintain normal function of the immune system.

Many products on the shelves of our preferred grocery store will claim to support or increase immunity. However scientifically, there is limited evidence of these claims and the Food and Drug Administration (FDA) has issued a warning against the use of such products.6 The CDC states the best source is of vitamins and minerals is through food as most dietary supplements come with unwanted side effects and may have interactions with certain medications and health conditions.1

Below we will discuss supplements that are associated with immune boosting properties.

  • Vitamin D is an important immune strengthening nutrient that can potentially reduce the risks of colds and the flu. Previous research has shown individuals with lower Vitamin D levels are more prone to bacterial and viral infections however clinical trials are needed to define the relationship between Vitamin D and COVID-19 severity and mortality.7
  • Vitamin C has a role in helping the immune system protect the body from viral and bacterial disease. Research has shown that regular supplementation of Vitamin C decreases the length of a common cold but does not reduce the risk of contracting a cold.8 Studies assessing the relationship between Vitamin C and COVID-19 are currently underway.
  • Zinc helps our body’s natural defense system fight off invading bacteria and viruses and has a prominent role in wound healing. Previous research has shown that elderly and children with low levels of zinc may have a higher risk of developing pneumonia and research suggests that zinc lozenges helps shorten the length of recovery and reduces symptoms for the common cold if taken within 24 hours of onset.9 Due to its role in immune function, the benefit of zinc in patients with COVID-19 is currently under investigation.
  • Garlic supplements are often reported to have numerous health benefits. There is limited evidence on the effect on upper respiratory infections however it may help reduce the frequency of upper respiratory infections and the duration of a cold10.
  • Honey is natural product that has been reported to exert antioxidant, antimicrobial, and anti-inflammatory effects. It was found to be helpful in coughs and sore throats and in improving upper respiratory tract infections11.

It is important to note these supplements have not been proven to be directly effective against COVID-19, but their role in respiratory infections and colds is worth noting. As outlined by the CDC the best way to prevent illness is to avoid exposure to the virus. Frequently washing hands with soap and water for at least 20 seconds, use of hand sanitizer (with at least 60% alcohol), maintaining a six feet distance with people, and wearing a mask in public settings are still the best ways to protect yourself12.



  1. Food and Coronavirus Disease 2019 (COVID-19). Centers for Disease Control and Prevention. Published 2020. Accessed September 5, 2020.
  2. How to boost your immune system. Harvard Health Publishing. Published 2020. Accessed September 6, 2020.
  3. Morey JN, Boggero IA, Scott AB, Segerstrom SC. Current directions in stress and human immune function. Current Opinion in Psychology. 2015;5:13-17. doi:10.1016/j.copsyc.2015.03.007
  4. Meditation: In Depth. National Center for Complementary and Integrative Health. Published 2020. Accessed September 6 2020.
  5. Grande AJ, Keogh J, Silva V, Scott AM. Exercise versus no exercise for the occurrence, severity, and duration of acute respiratory infections. Cochrane Database of Systematic Reviews. 2020. doi:10.1002/14651858.cd010596.pub3
  6. Fraudulent COVID-19 Products. U.S. Food and Drug Administration. Published 2020. Accessed September 6, 2020.
  7. Olena A. Trials Seek to Answer if Vitamin D Could Help in COVID-19. The Scientist Magazine®. Published 2020. Accessed September 6, 2020.
  8. Office of Dietary Supplements – Vitamin C. NIH Office of Dietary Supplements. Published 2019. Accessed September 6, 2020.
  9. Office of Dietary Supplements – Zinc. NIH Office of Dietary Supplements. Published 2019. Accessed September 6, 2020.
  10. Boost the Immune System. University of Maryland Medical System. Accessed September 7, 2020.
  11. Abuelgasim H, Albury C, Lee J. Effectiveness of honey for symptomatic relief in upper respiratory tract infections: a systematic review and meta-analysis. BMJ Evidence-Based Medicine. 2020. doi:10.1136/bmjebm-2020-111336
  12. How to Protect Yourself & Others. Centers for Disease Control and Prevention. Published 2020. Accessed September 7, 2020.