“I would suspect that a dose of 2,000 IU taken weeks and weeks during the viral season in the fall and winter, and maybe boosting at the time of infection or first symptoms to 3,000 IU, would be promising in reducing Long COVID,” she speculates. “So you’d be at a steady state and would have reached an equilibrium in terms of having active vitamin D in your system to help reduce the severity of symptoms at the time of acute infection. Then if you add a little more—another 1,000 IUs a day—it might reduce Long COVID.”
That strategy would have to be tested and validated in a rigorous study, but Manson says it’s a reasonable hypothesis to explore further given what’s now known about vitamin D and its ability to support the immune system. If future studies bear out these findings, she says vitamin D supplements could become a useful tool in helping people better control the symptoms of other viral infections as well. At such doses, vitamin D is relatively safe, and in her studies, Manson didn’t identify any serious adverse events related to the supplement. Extremely high doses of vitamin D taken over long periods of time can lead to abnormal buildup of calcium and kidney stones, as well as irregular heartbeat, but the doses that could potentially be helpful in controlling viral infections are much lower, and people would only be taking them seasonally, when the risk of infections is higher. “This is the first trial looking at this question,” she says, “and further research is warranted.”
