Modest effects of dietary supplements during the pandemic: probiotics have a role to play

In this independent study, the investigators of the 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 general population 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.

The Symptom Study app was developed by health data company Zoe Global with input from King’s College London, the Massachusetts General Hospital, Lund University, Sweden and Uppsala University, Sweden. The app enabled self-reported information related to infection to be captured. On first use, the app recorded self-reported location, age and core health risk factors. With continued use, participants provided daily updates on symptoms, healthcare visits, test results and if they were self-quarantining or seeking healthcare, including the level of intervention and related outcomes.

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.

Assumptions stated in the discussion part of the publication on probiotics are that “probiotics modify the host’s gut microbiota and may generate antiviral metabolites, and interact with the host’s gut-associated immune system. This can result in improved immunity, including enhanced responses to the seasonal influenza vaccine. Mechanistic studies support a gut-lung axis, whereby immune effects of microbiota at the gut level can be transferred to the lung, most likely through movement of immune cells. This could explain why some probiotic organisms reduce risk and severity of respiratory tract infections.”

Randomized controlled trials are required to confirm these observational findings before any therapeutic recommendations can be made.


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