Vitamin D supplements may offer researchers a new clue about lingering COVID symptoms that persist after infection, according to a new study.
Researchers at Mass General Brigham examined whether high doses of vitamin D could influence COVID-19 outcomes, including the risk of developing long COVID, a condition in which symptoms such as fatigue, shortness of breath and brain fog continue weeks or months after the initial infection.
The findings were published in The Journal of Nutrition.
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The randomized clinical trial included 1,747 adults who had recently tested positive for COVID-19, along with 277 members of their households. Participants were assigned to receive either vitamin D3 supplements or a placebo for four weeks.
Dr. JoAnn Manson, senior author of the study and a physician at Mass General Brigham, told Fox News Digital that the results point to a possible benefit related to long-term symptoms.
"A key takeaway is that vitamin D supplementation looks promising for reducing the risk of developing long COVID but does not appear to affect the severity of the acute infection," Manson said.
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Researchers found that vitamin D supplementation did not significantly change short-term outcomes such as symptom severity, hospital visits or emergency care.
The study also showed no difference between the vitamin D and placebo groups in the likelihood that household contacts would contract the virus.
However, when researchers analyzed participants who closely followed the supplement regimen, they observed a possible difference in lingering symptoms.
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About 21% of participants who took vitamin D reported at least one ongoing symptom eight weeks after infection, compared with 25% of those who received a placebo.
"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," Manson said in the press release.
"While we didn't find that high-dose vitamin D reduced COVID severity or hospitalizations, we observed a promising signal for long COVID that merits additional research," she added.
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Manson said vitamin D may influence longer-term complications because the nutrient plays a role in regulating inflammation in the body.
The researchers noted several limitations in the trial. The study had to be conducted remotely during the pandemic, and participants began taking vitamin D several days after their COVID diagnosis.
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Ideally, Manson said, supplementation would begin before infection or immediately after diagnosis.
She added that larger studies will be needed to confirm whether vitamin D could reduce the risk or severity of long COVID symptoms.
Researchers are planning additional trials to examine whether vitamin D supplementation may help treat people already experiencing long COVID.
