Taking multivitamins, omega-3s, probiotics or vitamin D supplements may reduce the risk of positive testing for SARS-CoV-2, the virus responsible for COVID-19 infection – at least among women – according to a large population-based study published online in the journal BMJ Nutrition Prevention and Health.
But taking any vitamin C, zinc or garlic supplement is not associated with a lower risk of positive virus tests, the findings show.
Scientists have supported the use of dietary supplements to deter and treat COVID-19 infection since the onset of the pandemic, the researchers note.
In the UK alone, market share rose 19.5% in the period leading up to the first national ‘lock-in’ on March 23 last year, with vitamin C sales up 110% and multivita sales up 93%.
Similarly, sales of zinc supplements rose 415% in the first week of March, at the height of fears of COVID-19 in the United States.
Dietary supplements may help support a healthy immune system, but whether certain supplements may be associated with a lower risk of SARS-CoV-2 infection is unknown.
In a search to close this knowledge gap, the researchers relied on adult users of the COVID-19 Symptom Study to determine whether regular supplement users were less likely to test positive for SARS-CoV-2.
The app was launched in the UK, US and Sweden in March 2020 to gather information on pandemic developments they reported themselves.
Initially, it recorded the location, age, and key health risk factors of its users. But as time went on, subscribers were asked to provide daily news on a range of issues, including symptoms, coronavirus test results and healthcare. People without obvious symptoms are also encouraged to use it.
For the purposes of this study, the researchers analyzed information provided by 372,720 UK subscribers to the application about their regular use of dietary supplements during May, June and July 2020 during the first wave of the pandemic, as well as coronavirus swab test results.
Between May and July, 175,652 UK subscribers regularly took dietary supplements, and 197,068 did not. Approximately two-thirds (67%) were women and more than half were overweight (BMI of 27).
A total of 23,521 individuals tested positive for SARS-CoV-2 and 349,199 tested negative for May-July.
Taking probiotics, omega-3 fatty acids, multivit or vitamin D is associated with a lower risk of SARS-CoV-2 infection: by 14%, 12%, 13% and 9%, respectively, after taking into account potentially influencing factors , including basic conditions and normal diet.
No such effects have been observed in those taking vitamin C, zinc or garlic supplements.
And when researchers specifically looked at gender, age, and weight (BMI), protective associations for probiotics, omega-3 fatty acids, multivitis, and vitamin D were only observed in women of all ages and weights. No such clear associations were observed in men.
Despite some differences, the same overall patterns were reflected in both U.S. (45,757) and Swedish (27,373) subscribers.
Equivalent data for the US and Sweden were a reduced risk of: 18% and 37% for probiotics, respectively; 21% and 16% for omega-3 fatty acids, respectively; 12% and 22%, respectively, for multivits; and 24% and 19%, respectively, for vitamin D supplements.
This is an observational study and as such cannot determine the cause. 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 dosages of additives or ingredients.
But while the effects observed were modest, they were significant, the researchers note, calling for large clinical trials to report evidence-based therapeutic recommendations.
“We know that through micronutrients, including vitamin D, it is necessary for a healthy immune system to function. This in turn is key to preventing and recovering from infections.
“But to date, there is little convincing evidence that taking nutritional supplements has any therapeutic value other than maintaining the body’s normal immune response,” comments Professor Sumantra Ray, executive director, NNEdPro Global Center for Nutrition and Health, which co-owns the journal.
Moreover, this study is not primarily designed to answer questions about the role of dietary supplements in COVID-19. This is still a new area of research that requires further rigorous studies before firm conclusions can be drawn as to whether certain dietary supplements may reduce the risk of COVID-19 infection. ”
Sumantra Ray, CEO, NNEdPro Global Center for Nutrition and Health
Louca, P., and others. (2021) Modest effects of dietary supplements during the COVID-19 pandemic: insight from 445,850 users of the COVID-19 Symptom Study application. BMJ Nutrition Prevention and Health. doi.org/10.1136/bmjnph-2021-000250.