Taking multivitamins, omega-3, probiotics or vitamin D supplements may reduce the risk of testing positive for the novel coronavirus which causes COVID-19, at least among women, according to a large observational study. The research, published in the journal BMJ Nutrition Prevention & Health, found that taking vitamin C, zinc, or garlic supplements was not associated with a lower risk of testing positive for the virus, the findings show.
The researchers, including those from King's College London in the UK, drew on adult users of the COVID-19 Symptom Study app to see if regular supplement users were less likely to test positive for SARS-CoV-2.
The app was launched in the UK, the US, and Sweden in March 2020 to capture self-reported information on the evolution of the pandemic.
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 as well as any coronavirus swab test results.
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Between May and July, 175,652 UK subscribers regularly took dietary supplements while197,068 did not. Around two thirds (67 per cent) were women and over half were overweight.
In all, 23,521 people tested positive for SARS-CoV-2 and 349,199 tested negative between May and July.
The study found taking probiotics, omega fatty acids, 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.
No such effects were observed among those taking vitamin C, zinc, or garlic supplements, according to the researchers.
When the researchers looked specifically at sex, age and weight (BMI), the protective associations for probiotics, omega-3 fatty acids, multivitamins and vitamin D were observed only in women of all ages and weights.
No such clear associations were seen in men, the researchers said.
Despite some differences, the same overall patterns were mirrored in both the US (45,757) and Swedish (27,373) subscribers, they said.
The researchers noted that this is an observational study, and as such, can not establish cause.
They 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.
Although the observed effects were modest, they were significant, noted the researchers, who call for large clinical trials to inform evidence-based therapeutic recommendations.
"We know that a range of micronutrients, including vitamin D, are essential for a healthy functioning immune system. This, in turn, is key to prevention of, and recovery from, infections," said Professor Sumantra Ray, Executive Director, NNEdPro Global Centre for Nutrition and Health, which-co-owns the journal.
"But to date, there is little convincing evidence that taking nutritional supplements has any therapeutic value beyond maintaining the body's normal immune response," Ray added.
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