Taking multivitamins, omega-3, probiotics or vitamin D supplements may lessen the risk of testing positive for a COVID-19 infection, at least among women, according to a new large population study.
But taking any vitamin C, zinc or garlic supplements wasn't associated with a lower risk of testing positive for the virus, the findings show.
Nutrition supplements can help to support a healthy immune system, but whether specific supplements might be associated with a lower risk of catching COVID-19 isn't known.
The COVID-19 Symptom Study app
To learn more about this, the researchers 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.
Initially, it 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.
About the study
For this study, the researchers analysed information provided by 372,720 UK subscribers to the app about their regular use of nutrition supplements throughout May, June, and July 2020 during the first wave of the pandemic as well as any coronavirus swab test results.
Between May and July, 175,652 UK subscribers regularly took dietary supplements while 197,068 did not. Around two thirds (67%) 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.
Probiotics, omega-3’s, multis, vitamin D tied to fewer positive tests
Taking probiotics, omega-3 fatty acids, multivitamins or vitamin D was associated with a lower risk of a COVID-19 infection. That was after accounting for factors that could influence the risk of infection including underlying conditions and usual diet.
No such effects were observed among those taking vitamin C, zinc, or garlic supplements.
The protective link between probiotics, omega-3 fatty acids, multivitamins and vitamin D were observed only in women of all ages and BMIs (body mass index). No clear associations were seen in men.
The same overall patterns were mirrored in both the US (45,757) and Swedish (27,373) subscribers.
Study limitations
This is an observational study, and as such, can't prove cause and effect. The researchers also acknowledge 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, however, significant, note 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. But to date, there is little convincing evidence that taking nutritional supplements has any therapeutic value beyond maintaining the body's normal immune response”.
This is still an emerging area of research that warrants further rigorous study before firm conclusions can be drawn about whether specific nutritional supplements might help reduce the risk of COVID-19 infection.
Source: BMJ Nutrition, Prevention & Health, March 4, 2021.
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