As a result, vitamin D has drawn a lot of interest because of its ability to prevent and treat COVID-19. But most studies are observational and have produced conflicting findings.
The first trial, which recruited 6,200 adults (16 years and older) who were not taking vitamin D supplements at the time of enrollment, was conducted in the UK between December 2020 and June 2021.
A vitamin D blood test was made available to half of the participants (3,100). People with low levels (2,674; 86%) were given either 3200 IU/day or 800 IU/day of vitamin D supplements for six months. The other half (controls) got neither a test nor pills.
Over a six-month follow-up period, neither vitamin D dose impacted the number of identified acute respiratory tract infections or COVID-19 cases. No significant adverse event was linked to study supplements, and the number of adverse events was comparable among groups.
The second trial, which used cod liver oil and had low levels of vitamin D and A and omega-3 fatty acids, was conducted in Norway between November 2020 and June 2021.
About 34,741 adults (18-75 years old) who did not use vitamin D supplements were given 5 mL of cod liver oil or 5 mL of corn oil as a placebo every day for six months. Most subjects (86%) who underwent testing began the trial with sufficient vitamin D levels.
Once more, when compared to a placebo, the researchers discovered no difference between cod liver oil and acute respiratory infections or PCR-confirmed COVID-19. Only mild adverse effects, compared to the placebo group, were experienced by the cod liver oil group.
The results should be evaluated further because both studies used a highly efficient vaccine.
Does Vitamin D Protect Against COVID-19?
Despite this, both studies had several advantages, such as excellent levels of participant compliance and the use of RT-PCR swab tests to confirm infections. The findings support other studies that demonstrated no protective impact of vitamin D on the risk of COVID-19.
Vitamin D supplements do not appear to lower the incidence of COVID-19 or other acute respiratory infections.
In a related editorial, Professor Peter Bergman of the Karolinska Institutet in Sweden suggested that immunization remains the most reliable method of preventing COVID-19 infection. Vitamin D and cod liver oil supplements should not be given to healthy individuals with normal vitamin D levels.
Instead, he advises that clinicians must concentrate on high-risk populations, such as those with dark skin or skin that gets little sun exposure, pregnant women and older people with chronic conditions.