Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2025 Feb 22;17(2):e79452.
doi: 10.7759/cureus.79452. eCollection 2025 Feb.

Public Interest in Vitamin C Supplementation During the COVID-19 Pandemic as a Potential Risk for Oxalate Nephrolithiasis

Jayson P Kemble  1 , Christine W Liaw  2 , Jamal M Alamiri  3 , Garrett N Ungerer  4 , Aaron M Potretzke  4 , Kevin Koo  4
Affiliations

Public Interest in Vitamin C Supplementation During the COVID-19 Pandemic as a Potential Risk for Oxalate Nephrolithiasis

Jayson P Kemble et al. Cureus. .

Abstract

Introduction: Vitamin C (ascorbic acid) therapy was widely touted as a potential treatment or preventive therapy for COVID-19 despite a lack of supporting evidence. One potential harm of high-dose vitamin C supplementation is increased urinary oxalate, which may increase the risk of hyperoxaluria and oxalate kidney stones. This study aims to evaluate public interest in vitamin C during the COVID-19 pandemic based on online search volume and to characterize variation in vitamin C interest as a potential contributor to kidney stone formation. Methods: The volume and frequency of online search traffic related to vitamin C and COVID-19 were assessed using the Google Trends platform (Google LLC, Mountain View, CA, USA) between 2018 and 2022. Weekly relative search volumes (RSV), the proportional volume of online searches for a search term, were assessed to compare variations in online interest in vitamin C and COVID-19. The most popular Google search results for vitamin C as a treatment for COVID-19 were assessed for medical accuracy. Statistical analysis was performed with t-tests and linear regression.

Results: Online search volume for vitamin C increased four-fold at the onset of COVID-19 in March 2020. After the initial outbreak, average RSV for vitamin C remained significantly elevated compared to pre-COVID-19 levels (37.7 vs. 25.1, p<0.001). Weekly RSV for vitamin C increased steadily during the study period (R2=0.59, p<0.001). The peak in online interest in vitamin C corresponded to increased online search volume during three global COVID-19 surges. Among the most popular results for COVID-19-related vitamin C queries, 30% inaccurately suggested that vitamin C had potential benefits in treating COVID-19. None of these search results discussed the potential increased risk of kidney stones with vitamin C supplementation.

Conclusion: Online public interest in vitamin C supplementation increased and remained elevated during the COVID-19 pandemic. These findings have implications for increased risk of hyperoxaluria and oxalate stones due to vitamin C supplementation. Kidney stone patients should be counseled that excess vitamin C intake is associated with increased urinary oxalate and incident stone formation.

Keywords: covid-19; nephrolithiasis; oxalate; pandemic; vitamin c.

PubMed Disclaimer

Conflict of interest statement

Human subjects: Consent for treatment and open access publication was obtained or waived by all participants in this study. Animal subjects: All authors have confirmed that this study did not involve animal subjects or tissue. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: Kevin Koo declare(s) royalties from UpToDate, Inc. Kevin Koo received royalties from UpToDate, Inc., unrelated to the study. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.

Figures

Figure 1
Figure 1. Online search interest in vitamin C
Searches for vitamin C during the COVID-19 outbreak in March 2020 were four times higher than any previous peak. Subsequent outbreaks also led to diminished surges in online interest, about half the volume of the initial peak in early 2020.
Figure 2
Figure 2. Weekly variation in online interest in vitamin C
Linear regression for vitamin C searches by week, excluding the three-month peak surrounding the initial COVID-19 outbreak (R2=0.59; p<0.001).
Figure 3
Figure 3. Comparative analysis of online search interest between vitamin C and COVID-19 surges
Similar spikes in search patterns emerged during the initial outbreak in March 2020 and subsequent surges of COVID-19 variants (UK variant in December 2020, delta variant in July 2021, and omicron variant in early 2022).
See this image and copyright information in PMC

References

    1. Dietary supplements and nutraceuticals market growth during the coronavirus pandemic — Implications for consumers and regulatory oversight. Lordan R. PharmaNutrition. 2021;18:100282. - PMC - PubMed
    1. The long history of vitamin C: from prevention of the common cold to potential aid in the treatment of COVID-19. Cerullo G, Negro M, Parimbelli M, et al. Front Immunol. 2020;11:574029. - PMC - PubMed
    1. Coronavirus Disease 2019 (COVID-19) Treatment Guidelines. [ Aug; 2022 ]. 2022. https://www.covid19treatmentguidelines.nih.gov https://www.covid19treatmentguidelines.nih.gov
    1. Contribution of dietary oxalate and oxalate precursors to urinary oxalate excretion. Crivelli JJ, Mitchell T, Knight J, Wood KD, Assimos DG, Holmes RP, Fargue S. Nutrients. 2020;13:62. - PMC - PubMed
    1. What stone-formers should know about vitamin C and D supplementation in the COVID-19 era. Khusid JA, Atallah WM, Kyprianou N, Gupta M. Eur Urol Open Sci. 2020;21:9–11. - PMC - PubMed

LinkOut - more resources