Vitamin C supplements, colds and COVID-19: what the evidence shows
What it found
In people, regular vitamin C supplements do not prevent colds in the general population, though they may slightly shorten a cold.
The authors say there is no evidence that vitamin C protects against SARS-CoV2 infection.
What they found
Studies in people
Common cold prevention
In the general population, regular vitamin C supplements do not prevent the common cold. A meta-analysis of 8,472 people found strong evidence that intake above 80 mg per day does not prevent colds in healthy adults and children.
Cold duration
Vitamin C may slightly shorten a cold. In children, supplementation reduced the duration of upper respiratory tract infections by 14%.
Heavy physical stress
In people under extreme physical stress, such as soldiers and athletes, vitamin C may reduce the incidence of colds by about 50%. A trial in 1,444 Korean soldiers found a 0.80-fold lower risk of getting a cold with 6 g per day for 30 days.
Pneumonia
Evidence on vitamin C for preventing or treating pneumonia is insufficient. A meta-analysis of 2,774 participants found very low quality evidence.
COVID-19 prevention
No data are available on whether oral vitamin C reduces the risk of SARS-CoV2 infection in healthy people. The authors say there is no evidence that vitamin C supplementation protects against SARS-CoV2 infection.
Intravenous vitamin C in critical illness
In ICU patients with sepsis or ARDS, intravenous vitamin C has shown mixed results. Some trials found reduced ventilation time and lower mortality, but meta-analyses did not confirm a benefit on mortality.
What the authors conclude
“Although a significant increase in vitamin C sales was registered immediately after the global pandemic state of emergency was declared, at present, there is no evidence that vitamin C supplementation can protect people from the SARS-CoV2 infection.”
Also in their conclusions
- They conclude that the evidence is insufficient to support regular vitamin C supplementation for preventing or treating the common cold or pneumonia in the general population.
- They state that there is no evidence that vitamin C supplementation can protect people from SARS-CoV2 infection.
- They advise that health care professionals should ensure patients have correct information about the lack of data supporting vitamin C for COVID-19.
How it was done
The authors wanted to clarify whether vitamin C supplements can prevent or treat respiratory infections, including COVID-19, given widespread popular belief and market claims.
They reviewed published studies on vitamin C and immune function, common cold, pneumonia, and critical illness, including randomised trials in adults and children and meta-analyses.
What it can’t tell you
- This is a review of published studies, so it cannot provide new experimental evidence.
- Many of the studies included had limitations, such as small numbers of participants or different populations, so the findings may not apply to everyone.
- The authors note that further randomised trials are needed, especially in COVID-19 patients.
Who paid
- Authors work at
- University of Naples Parthenope, Italy; University of Pavia, Italy; University of Salerno, Italy
The paper
- Title
- The Long History of Vitamin C: From Prevention of the Common Cold to Potential Aid in the Treatment of COVID-19
- Type
- ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Cerullo G, Negro M, Parimbelli M, et al (2020). The Long History of Vitamin C: From Prevention of the Common Cold to Potential Aid in the Treatment of COVID-19. Frontiers in immunology. doi:10.3389/fimmu.2020.574029Free full textPubMed 33193359DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error