Taking multivitamins, omega-3, probiotics or vitamin D supplements may lessen the risk of testing positive for SARS-CoV-2, the virus responsible for Covid-19 infection, at least among women, a new UK study has revealed.
The study, by researchers from King’s College London and published in the journal ‘BMJ Nutrition Prevention & Health’, also found that taking vitamin C, zinc or garlic supplements wasn’t associated with a lower risk of testing positive for the deadly virus. The research drew on adult users of an app, called the Covid-19 Symptom Study app, to see if regular supplement users were less likely to test positive for Covid-19. For the purposes of the study, the researchers analysed information supplied by 372,720 UK subscribers to the app about their regular use of dietary supplements throughout May, June, and July 2020 during the first wave of the pandemic in the country, as well as any coronavirus swab test results.
“Taking probiotics, omega-3 fatty acids, multivits (multivitamins) or vitamin D was associated with a lower risk of SARS-CoV-2 infection: by 14 per cent, 12 per cent, 13 per cent and 9 per cent, respectively, after accounting for potentially influential factors, including underlying conditions and the overall quality of each person’s diet,” the study finds.
“No such effects were observed among those taking vitamin C, zinc or garlic supplements. And when the researchers looked specifically at sex, age and weight (BMI), the protective associations for probiotics, omega-3 fatty acids, multivits and vitamin D were observed only in women of all ages and weights. No such clear associations were seen in men,” it notes.
The Covid-19 Symptom Study app was launched in the UK, the US, and Sweden in March 2020 to capture self-reported information on the evolution of the pandemic. Initially, the app recorded the location, age and core health risk factors of its users. But as time went on, subscribers were asked to provide daily updates on a range of issues, including symptoms, coronavirus test results, and healthcare. People without obvious symptoms were also encouraged to use it.
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According to the data gathered, between May and July, 175,652 UK subscribers regularly took dietary supplements; 197,068 didn’t. Around two thirds (67 per cent) were women and over half were overweight (BMI of 27). In all, 23,521 people tested positive for SARS-CoV-2 and 349,199 tested negative between May and July.
Despite some differences, the same overall patterns were mirrored in both the US (45,757) and Swedish (27,373) subscribers. The equivalent figures for the US and Sweden were a reduced risk of: 18 per cent and 37 per cent, respectively for probiotics; 21 per cent and 16 per cent, respectively, for omega-3 fatty acids; 12 per cent and 22 per cent, respectively for multivits; and 24 per cent and 19 per cent, respectively, for vitamin D supplements.
"This is an observational study, and as such, can’t establish cause," the study points out.
The researchers also acknowledge several limitations, including that the study relied on self reported data and a self selected group. No information was collected on supplement doses or ingredients either.
But although the observed effects were modest, they were significant, which calls for large clinical trials to inform evidence-based therapeutic recommendations, it is recommended.
The researchers noted celebrity endorsement of the use of dietary supplements to both ward off and treat Covid-19 infection since the start of the pandemic. In the UK alone, market share rose by 19.5 per cent in the period leading up to the first national lockdown on March 23 last year, with sales of vitamin C rising by 110 per cent and those of multivitamins by 93 per cent.
Similarly, zinc supplement sales rose by 415 per cent in the first week of March, at the height of Covid-19 fears in the US.
Dietary supplements can help to support a healthy immune system, but whether specific supplements might be associated with a lower risk of catching SARS-CoV-2 remains to be deeply analysed.