A decade-old peer-reviewed paper published in the journal Nutrients has reignited discussions about vitamin D recommendations. The 2014 analysis, led by researchers from the University of Alberta, Creighton University, and GrassrootsHealth, re-examined the statistical methodology used by the Institute of Medicine (IOM) in 2011 to establish the current Recommended Dietary Allowance (RDA) for vitamin D at 600 IU per day. The study found that this level is insufficient; correcting the statistical approach revealed that approximately 8,895 IU daily would be required to ensure 97.5% of healthy adults achieve a protective blood concentration of at least 50 ng/mL.

The research has gained renewed attention due to persistent vitamin D deficiency rates in North America (40–50% of the population) and growing evidence linking higher levels of vitamin D (30–40 ng/mL or above) with reduced risks of respiratory infections, certain cancers, autoimmune diseases, and all-cause mortality. A subsequent meta-analysis published in Nutrients found that vitamin D supplementation was associated with about a 60% reduction in the incidence of COVID-19 infection in randomized controlled trials and up to 70% effectiveness in reducing severe outcomes requiring intensive care.

A large study published in the journal Nature, analyzing data from over 600,000 U.S. veterans, found that vitamin D3 supplementation was linked to a 33% lower risk of death within 30 days of COVID-19 infection compared to non-supplemented individuals. Vitamin D2 supplementation showed a 28% reduction in infection rates. The study also indicated that individuals with low initial vitamin D levels (below 20 ng/mL) who received high-dose supplements experienced up to a 49% reduction in infection risk.

The National Academy of Medicine, which succeeded the IOM, has not updated its guidance on vitamin D since 2011. A U.S. government official previously stated that a study did not show effectiveness of vitamin D for treating COVID-19, but recent research contradicts this claim.