Vitamin D Supplements, Cod Liver Oil Do Not Reduce COVID-19 Risk
THURSDAY, Sept. 8, 2022 (HealthDay News) — Neither vitamin D supplementation nor cod liver oil supplementation reduce the risk for COVID-19 infection or serious COVID-19, according to two studies published online Sept. 7 in The BMJ.
David A. Jolliffe, Ph.D., from the Queen Mary University of London, and colleagues conducted a phase 3 randomized trial involving 6,200 people aged 16 years and older. A total of 3,100 individuals were offered a vitamin D test; 2,674 had 25-hydroxyvitamin D <75 nmol/L and received supplements (1,328 lower dose; 1,346 higher dose); 3,100 were not offered testing or supplementation. The researchers found that at least one acute respiratory tract infection occurred in 5.7 and 5.0 percent of the lower- and higher-dose groups, respectively, compared with 4.6 percent in the no-offer group, although the differences were not significant. COVID-19 developed in 3.6 and 3.0 percent of those in the lower- and higher-dose groups, respectively, compared with 2.6 percent in the no-offer group, with the differences not statistically significant.
Sonja H. Brunvoll, Ph.D., from Oslo University Hospital in Norway, and colleagues randomly assigned 34,601 adults (aged 18 to 75 years) not taking daily vitamin D supplements to receive cod liver oil (17,278 participants) or placebo (17,323 participants). The researchers observed no association between supplementation with cod liver oil and a reduced risk for any of the coprimary end points (positive severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2] test result, serious COVID-19, negative SARS-CoV-2 test result, and self-reported symptoms, with the third and fourth indicating other acute respiratory infections).
“Vaccination is still the most effective way to protect people from COVID-19, and vitamin D and cod liver oil supplementation should not be offered to healthy people with normal vitamin D levels,” write the authors of an accompanying editorial.
Several authors from the Jolliffe study disclosed financial ties to the pharmaceutical and supplement industries; several authors from the Brunvoll study disclosed ties to the biopharmaceutical industry.