Know Your Medicines
Do Supplements Work for COVID-19 Prevention or Treatment?

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Take home message

Supplements work best if a person has a specific deficiency or need. If you are unsure whether you require a supplement, always speak to your doctor or pharmacist.

Currently there are no supplements that have been proven to treat or prevent COVID-19 infections. In this article, we will discuss some commonly used supplements that are marketed to have immune boosting effects and their presumed effects on common respiratory infections (eg common cold, influenza and pneumonia).

1 – Vitamin C

Vitamin C is important for supporting the immune response against infections.  People with vitamin C deficiency, or scurvy have poor wound healing, weakened immunity and are more susceptible to infections. The Health Promotion Board1 recommends an average daily intake of 100mg of Vitamin C from either food or dietary supplements to maintain good immune response. However, there is currently no evidence that taking vitamin C at above 100mg a day will boost the immune system.

Currently researchers at Zhong Wuhan University are studying the effects of megadose of vitamin C infusion (up to 24,000mg daily, 240 times higher than the required amount) on reducing excessive inflammatory symptoms caused by COVID-19 infection. However, the result will only be concluded when the study ends in September 20202.

2 – Vitamin D

Vitamin D is known to protect the body against inflammation, regulates and activates immune responses. Low levels of vitamin D have been associated with decreased lung function3, and increased risk of infections and immune-related disorders4-6.  

The Health Promotion Board recommends an average daily dose of 100 IU of vitamin D. To ensure adequate vitamin D, you may consider allowing the sun to shine on your arms and legs for 5 to 30 minutes, at least twice a week from 10am to 3pm7. Alternatively, taking supplementation of 400IU to 2000IU a day is reasonable5 for most adults who do not suffer from long term diseases which affect the kidney. Overconsumption of vitamin D should be avoided as the body cannot eliminate excess vitamin D and accumulation can lead to toxicity.

3 – Zinc

Zinc is an essential mineral for the immune system as it is involved in the development and communication of many immune cells. Zinc deficiency leads to increased risk of infections and diseases8. Children, who are prone to zinc deficiency due to reduced absorption, may receive the most benefit of zinc supplementation9. However, in children and adults with a balanced diet, zinc supplementation do not prevent respiratory illnesses. At best, 75mg zinc lozenges daily can help to soothe your throat and shorten the duration of the symptoms by 2 or 3 days10.

4 – Black elderberries

Black elderberries (Sambucus nigra) have long been used as a home remedy for cold and flu. Laboratory experiments have shown that black elderberries have antibacterial and antiviral properties11-12. However, few reliable studies have been done demonstrating its influenza preventing effects in humans. The largest study done on a human only involved 180 participants13. The result from this review showed a significant reduction in influenza symptoms in black elderberry users if taken within 48 hours of symptom onset.


  1. Health Promotion Board (2019). Recommended dietary allowances
  2. Vitamin C Infusion for the Treatment of Severe 2019-nCoV Infected Pneumonia (2020). Retrieved from
  3. Aranow C (2013). Vitamin D and the Immune SystemJournal of Investigative Medicine 2011;59:881-886
  4. Bergman P (2013) Vitamin D and Respiratory Tract Infections: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. PLoS ONE 8(6): e65835.
  5. Martineau A R (2017). Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ 2017;356:i6583
  6. Vitamin D: Recommended Dietary Allowances, Food Sources, and Side Effects. Retrieved from
  7. Prasad AS (2009). Zinc: Role in Immunity, Oxidative Stress and Chronic Inflammation. Curr Opin Clin Nutr Metab Care. 12(6):646–652.
  8. Lassi  ZS (2016). Zinc supplementation for the prevention of pneumonia in children aged 2 months to 59 months. Cochrane Database of Systematic Reviews, Issue 12. Art. No.: CD005978.
  9. Singh  M (2013)Zinc for the common cold. Cochrane Database of Systematic Reviews, Issue 6. Art. No.: CD001364. DOI: 10.1002/14651858.CD001364.pub4.
  10. Hemilä, H. (2017). Zinc lozenges and the common cold: a meta-analysis comparing zinc acetate and zinc gluconate, and the role of zinc dosage. JRSM Open
  11. Krawitz, C., et al. (2017) Inhibitory activity of a standardized elderberry liquid extract against clinically-relevant human respiratory bacterial pathogens and influenza A and B viruses. BMC Complement Altern Med 11, 16
  12. Torabian G (2019). Anti-influenza Activity of Elderberry (Sambucus nigra). Journal of Functional Foods 54, 353-360  
  13. Hawkins J (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


Authored by

Annie Tran Anh Nhi, Choo Yan Cheng & Kng Li Lin, Grace
Members of Pharmaceutical Society of Singapore 

30th Mar 2020