Vitamin D and COVID-19: Recent Research on Severity and Long COVID Risk

Recent findings from a large study led by researchers at Mass General Brigham suggest that while high-dose vitamin D supplementation doesn’t reduce the severity of COVID-19 infection, it may influence the risk of developing long COVID. The research, published in The Journal of Nutrition, adds to the growing body of evidence surrounding vitamin D’s role in immune health and its potential impact on COVID-19 outcomes.

The VIVID Trial: Investigating Vitamin D’s Impact

The study, known as the Vitamin D for COVID-19 (VIVID) Trial, aimed to clarify the relationship between vitamin D supplementation and COVID-19. “There’s been tremendous interest in whether vitamin D supplements can be of benefit in COVID, and this is one of the largest and most rigorous randomized trials on the subject,” explained senior author JoAnn Manson, MD, DrPH, of the Mass General Brigham Department of Medicine.

Researchers evaluated high-dose vitamin D3 supplementation among 1,747 adults recently diagnosed with COVID-19 and 277 of their household contacts across the United States, and Mongolia. Participants were randomized to receive either daily vitamin D3 (9,600 IU/day for two days followed by 3,200 IU/day) or a placebo for four weeks. The U.S. Portion of the trial ran from December 2020 to September 2022, while the Mongolia trial took place from September 2021 to April 2022.

The study design incorporated stratified randomization and statistical weighting to ensure balanced study groups, accounting for factors known to affect COVID-19 outcomes, including age, sex, body mass index, race/ethnicity, and COVID-19 vaccination status.

No Significant Impact on COVID-19 Severity or Transmission

The research team found no significant difference between the vitamin D and placebo groups regarding healthcare utilization (hospital stays, clinic visits, emergency room visits) or mortality rates over the four-week study period. Symptom severity was also comparable between the two groups. High-dose vitamin D supplementation did not reduce the likelihood of household contacts becoming infected with COVID-19.

A Potential Link to Long COVID?

However, analysis revealed a potential signal regarding long COVID. Participants who consistently adhered to the vitamin D regimen appeared somewhat less likely to report persistent symptoms eight weeks post-infection compared to those receiving a placebo. Specifically, 21% of participants taking vitamin D reported at least one lingering symptom, compared to 25% in the placebo group. This difference was considered borderline statistically significant.

“Long COVID, which can include symptoms of fatigue, shortness of breath, brain fog, other cognitive challenges and more, continues to significantly impact people’s lives,” Manson stated. “We hope to conduct further research in larger populations on whether long-term vitamin D supplementation reduces the risks and severity of long COVID.”

Looking Ahead

While this study doesn’t support the employ of high-dose vitamin D3 as a treatment for acute COVID-19, the potential signal regarding long COVID warrants further investigation. Future research will be crucial to determine whether long-term vitamin D supplementation can effectively mitigate the risks and severity of long COVID symptoms.