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Supplements reduce COVID risk in women but not men — Large observational study

Research has found that small but significant decreases in the risk of SARS-CoV-2 infection among females – but not males – who took multivitamins, vitamin D, omega-3 fatty acids, or probiotics.

Researchers at King’s College London analysed data from 1.4m users of the COVID Symptom Study app in the UK, the US, and Sweden. The participants answered questions about their regular use of dietary supplements.

“Our research is an observational study and not a clinical trial, so we can’t make strong recommendations based on the data we have,” cautions senior researcher Dr Cristina Menni, of the School of Life Course Sciences, at King’s.

“Until we have further evidence about the role of supplements from randomised controlled trials, we recommend following the National Health Service (NHS) guidelines on vitamin usage as part of a healthy, balanced diet,” she adds.


Study details
Dietary supplements during the COVID-19 pandemic: insights from 1.4M users of the COVID Symptom Study app – a longitudinal app-based community survey

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

Published in medRxiv on 27 November 2020

Dietary supplements may provide nutrients of relevance to ameliorate SARS-CoV-2 infection, although scientific evidence to support a role is lacking. We investigate whether the regular use of dietary supplements can reduce the risk of testing positive for SARS-CoV-2 infection in around 1.4M users of the COVID Symptom Study App who completed a supplement use questionnaire.
Longitudinal app-based community survey and nested case control study.
Subscribers to an app that was launched to enable self-reported information related to SARS-CoV-2 infection for use in the general population in three countries.
Main Exposure
Self-reported regular dietary supplement usage since the beginning of the pandemic.
Main Outcome Measures
SARS-CoV-2 infection confirmed by viral RNA polymerase chain reaction test (RT-PCR) or serology test. A secondary outcome was new-onset anosmia.
In an analysis including 327,720 UK participants, the use of probiotics, omega-3 fatty acids, multivitamins or vitamin D was associated with a lower risk of SARS-CoV-2 infection by 14%(95%CI: [8%,19%]), 12%(95%CI: [8%,16%]), 13%(95%CI: [10%,16%]) and 9%(95%CI: [6%,12%]), respectively, after adjusting for potential confounders. No effect was observed for vitamin C, zinc or garlic supplements. When analyses were stratified by sex, age and body mass index (BMI), the protective associations for 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. Results were further confirmed in a sub-analysis of 993,365 regular app users who were not tested for SARS-CoV-2 with cases (n= 126,556) defined as those with new onset anosmia (the strongest COVID-19 predictor).
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 in women. No clear benefits for men were observed nor any effect of vitamin C, garlic or zinc for men or women. Randomised controlled trials of selected supplements would be required to confirm these observational findings before any therapeutic recommendations can be made.


medRxiv study (Restricted access)


See also MedicalBrief archives:

Lancet removes hyped preprint on efficacy of vitamin D for COVID-19

Vitamin D supplementation: No benefit in preventing/treating COVID-19 — Consensus paper

More evidence of lack of Vitamin D efficacy for COVID-19 — Two studies

Still no definitive answer on Vitamin D3 to treat COVID-19

UK’s NICE review not recommending vitamin D to reduce risk of COVID-19

COVID-19 and vitamin D: SA experts say evidence is scant

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