RT Journal Article SR Electronic T1 Modest effects of dietary supplements during the COVID-19 pandemic: insights from 445 850 users of the COVID-19 Symptom Study app) JF BMJ Nutrition, Prevention & Health JO BMJ Nutrition FD BMJ Publishing Group Ltd SP bmjnph-2021-000250 DO 10.1136/bmjnph-2021-000250 A1 Panayiotis Louca A1 Benjamin Murray A1 Kerstin Klaser A1 Mark S Graham A1 Mohsen Mazidi A1 Emily R Leeming A1 Ellen Thompson A1 Ruth Bowyer A1 David A Drew A1 Long H Nguyen A1 Jordi Merino A1 Maria Gomez A1 Olatz Mompeo A1 Ricardo Costeira A1 Carole H Sudre A1 Rachel Gibson A1 Claire J Steves A1 Jonathan Wolf A1 Paul W Franks A1 Sebastien Ourselin A1 Andrew T Chan A1 Sarah E Berry A1 Ana M Valdes A1 Philip C Calder A1 Tim D Spector A1 Cristina Menni YR 2021 UL http://nutrition.bmj.com/content/early/2021/03/22/bmjnph-2021-000250.abstract AB 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.Data are available on reasonable request. Anonymised research data are shared with third parties via the centre for Health Data Research UK (HDRUK.ac.uk). US investigators are encouraged to coordinate data requests through the COPE Consortium (www.monganinstitute.org/cope-consortium). Data updates can be found on https://covid.joinzoe.com.