In this independent study, the investigators of the most recent and largest observational study on infection and dietary supplement use to date analyzed data from 445 850 subscribers of an app that was launched to enable self-reported information in the UK (n=372 720), the USA (n=45 757) and Sweden (n=27 373) in the first waves of the pandemic up to 31 July 2020.
In 372 720 UK participants (47% supplement users and 53% non-users), they observed the following modest but significant decrease of risk of infection:
- By 14% with probiotics (95% CI (8% to 19%))
- By 13% with multivitamins (95% CI (10% to 16%))
- By 12% with Omega 3 (95% CI (8% to 16%))
- By 9% with Vitamin D (95% CI (6% to 12%))
Of note, results in the US cohort and the Swedish cohort for probiotics were a decrease by 18% and 37% of the risk of infection respectively.
There was no significant results for vitamin C, zinc or garlic supplements.
On stratification by sex, age and body mass index (BMI), the protective associations were observed in females across all ages and BMI groups, but were not seen in men. The same overall pattern was observed in both the US and Swedish cohorts.
Randomized controlled trials are required to confirm these observational findings before any therapeutic recommendations can be made.