ABSTRACT
Introduction &Objective: High-dose vitamin C therapy is commonly believed to treat or protect against viral illnesses, such as seasonal influenza. However, not only is there a lack of supporting evidence for this practice, but high-dose vitamin C can also carry clinical risks. This includes its metabolic conversion to oxalate and resultant hyperoxaluria, which increases the risk of oxalate-based kidney stones. During the COVID-19 pandemic, there has been new interest in vitamin C therapy. This study aims to characterize public interest in vitamin C therapy and its association with nephrolithiasis. Method(s): The Google Trends platform was queried to assess worldwide searches for vitamin C, influenza, and COVID-19 using multiple related keywords. We analyzed search traffic from 2011 to 2021 for influenza and from 12/2019 to 9/2021 for COVID-19. To assess sources and accuracy of information about vitamin C therapy, we performed Google searches of "vitamin C COVID" and analyzed top results by support for the therapy and discussion of potential risks. Result(s): Online searches for vitamin C and influenza show a yearly chronicity with seasonal fluctuations (Fig. 1A). Online search traffic for vitamin C therapy paralleled interest in COVID (Fig. 1B). Subsequent peaks in COVID searches during the summer 2020, winter 2021, and summer 2021 surges were all associated with increased interest in vitamin C therapy. Among the top results for COVID-related vitamin C queries, most (90%) were medical websites or scientific publications. About a third of results stated without support that vitamin C may have potential benefit in treating COVID. No sources discussed the increased risk of kidney stones due to vitamin C therapy;only 1 source noted "potential adverse effects" but did not specify risks. Consistent with the lack of public information about stone risk, there were no apparent associations in search patterns between vitamin C or COVID and kidney stones (Fig. 1C). Conclusion(s): Online interest in vitamin C therapy reflects surges in COVID-19 incidence. Despite the known association between high-dose vitamin C and oxalate stones, no online sources discussing this therapy for COVID cited this risk. Continued public interest in COVID therapies may have unexpected epidemiological consequences including increased risk of kidney stones.