Modest effects of dietary supplements during the COVID-19 pandemic: insights from 445 850 users of the COVID-19 Symptom Study app.

Panayiotis Louca, Benjamin Murray, Kerstin Klaser, Mark S Graham, Mohsen Mazidi, Emily R Leeming, Ellen Thompson, Ruth Bowyer, David A Drew, Long H Nguyen, Jordi Merino, Maria Gomez, Olatz Mompeo, Ricardo Costeira, Carole H Sudre, Rachel Gibson, Claire J Steves, Jonathan Wolf, Paul W Franks, Sebastien Ourselin, Andrew T Chan, Sarah E Berry, Ana M Valdes, Philip C Calder, Tim D Spector, Cristina Menni

Journal: BMJ nutrition, prevention & health 2021;4(1):149-157

PMID: 34308122

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Plain Language Summary

A number of micronutrients, including vitamins C and D and zinc, have been shown to play key roles in supporting immune function and in reducing risk of respiratory infection. The aim of this study was to investigate whether users of the COVID-19 Symptom Study app who regularly took dietary supplements were less likely to test positive for SARS-CoV-2 infection. This study is an observational study on SARS-CoV-2 infection and dietary supplement use to date on over 400000 app users from three different countries. Results show a significant association between users of omega-3 fatty acid, probiotic, multivitamin or vitamin D supplements and lower risk of testing positive for infection with SARS-CoV-2 (particularly female users in the largest UK cohort). However, no effects were observed when taking zinc, vitamin C or garlic. Authors conclude that further studies testing the protective effects of specific supplements, and also possible adverse effects, on disease severity are required before any evidence-based recommendations can be made.

Abstract

OBJECTIVES

Dietary supplements may ameliorate SARS-CoV-2 infection, although scientific evidence to support such a role is lacking. We investigated whether users of the COVID-19 Symptom Study app who regularly took dietary supplements were less likely to test positive for SARS-CoV-2 infection.

DESIGN

App-based community survey.

SETTING

445 850 subscribers of an app that was launched to enable self-reported information related to SARS-CoV-2 infection for use in the general population in the UK (n=372 720), the USA (n=45 757) and Sweden (n=27 373).

MAIN EXPOSURE

Self-reported regular dietary supplement usage (constant use during previous 3 months) in the first waves of the pandemic up to 31 July 2020.

MAIN OUTCOME MEASURES

SARS-CoV-2 infection confirmed by viral RNA reverse transcriptase PCR test or serology test before 31 July 2020.

RESULTS

In 372 720 UK participants (175 652 supplement users and 197 068 non-users), those taking probiotics, omega-3 fatty acids, multivitamins or vitamin D had a lower risk of SARS-CoV-2 infection by 14% (95% CI (8% to 19%)), 12% (95% CI (8% to 16%)), 13% (95% CI (10% to 16%)) and 9% (95% CI (6% to 12%)), respectively, after adjusting for potential confounders. No effect was observed for those taking vitamin C, zinc or garlic supplements. On stratification by sex, age and body mass index (BMI), the protective associations in individuals taking probiotics, omega-3 fatty acids, multivitamins and vitamin D were observed in females across all ages and BMI groups, but were not seen in men. The same overall pattern of association was observed in both the US and Swedish cohorts.

CONCLUSION

In women, we observed a modest but significant association between use of probiotics, omega-3 fatty acid, multivitamin or vitamin D supplements and lower risk of testing positive for SARS-CoV-2. We found no clear benefits for men nor any effect of vitamin C, garlic or zinc. Randomised controlled trials are required to confirm these observational findings before any therapeutic recommendations can be made.

Address: Department of Twin Research and Genetic Epidemiology, King's College London, London, UK.; School of Biomedical Engineering & Imaging Sciences, King's College London, London, UK.; Clinical & Translational Epidemiology Unit, Massachusetts General Hospital, Boston, Massachusetts, USA.; Department of Clinical Sciences, Lund University, Lund, Sweden.; MRC Unit for Lifelong Health and Ageing at UCL, University College London, London, UK.; Department of Nutritional Sciences, King's College London, London, UK.; Zoe Global Limited, London, UK.; Department of Twin Research and Genetic Epidemiology, King's College London, London, UK.; Division of Rheumatology, Orthopaedics and Dermatology, School of Medicine, University of Nottingham, Nottingham, Nottinghamshire, UK.; Human Development & Health, Faculty of Medicine, University of Southampton, Southampton, UK.

DOI: 10.1136/bmjnph-2021-000250