Now, with COVID-19 still threatening the nation, health experts are scrambling to find out if vitamin D could also aid in the prevention and treatment of the disease.
In a recent study, a team of scientists from Iran's Tehran University of Medical Sciences (TUMS) and the Boston University Medical Campus (BUMC) found that serum vitamin D levels and adverse clinical outcomes among COVID-19 patients were significantly correlated.
Published in the journal PLOS ONE, their findings show that hospitalized patients who were vitamin D sufficient had lower concentrations of C-reactive protein (CRP) -- a biomarker of inflammation -- in their blood and a 52 percent lower risk of death than patients who were either insufficient or deficient.
Moreover, patients with sufficient levels of vitamin D had more disease-fighting white blood cells than those with 25-hydroxyvitamin D (25(OH)D) levels lower than 30 ng/mL.
Given these findings, senior author Michael Holick said that their research offers direct evidence that vitamin D can reduce the risk of death and complications like cytokine storm, an overreaction of the immune system that leads to poor clinical outcomes, among COVID-19 patients.
The Sun is the most accessible and abundant source of vitamin D. Spending some time under the sun can help raise vitamin D levels and stave off health issues that arise from vitamin D deficiency.
However, the researchers noted that despite Iran's hot climate, vitamin D deficiency is prevalent among older adults. Coincidentally, older adults tend to suffer more severe outcomes upon contracting COVID-19.
To determine if a person's vitamin D status influences this, Holick and his colleagues measured the serum vitamin D levels of 235 COVID-19 patients admitted to TUMS Sina Hospital. Around 37 percent of the patients were aged 65 years or older. The researchers defined vitamin D sufficiency as having 25(OH)D levels equal to or greater than 30 ng/mL. Only 32.8 percent of the patients were found to be sufficient.
The researchers then followed all of the patients for clinical outcomes, which include severe infection, becoming unconscious and breathing difficulties that result in death. They also looked at the patients' blood CRP levels, which give a measurment of the severity of inflammation.
In addition, the researchers analyzed the patients' lymphocyte, or white blood cell, counts. Higher than normal lymphocyte counts are common in people who have had a recent viral infection. The researchers then compared the severity of COVID-19 outcomes between vitamin D deficient or insufficient patients and vitamin D sufficient patients.
The researchers found that vitamin D sufficient patients aged 40 and above had a 51.5 percent lower risk of death due to COVID-19 than vitamin D insufficient or deficient patients. Vitamin D deficiency is defined as having 25(OH)D levels below 20 ng/mL.
Moreover, vitamin D sufficient patients had a lower risk of becoming unconscious or having breathing difficulties that could lead to death. These patients also had lower levels of CRP and higher lymphocyte counts, indicating better immune response to the infection.
Meanwhile, vitamin D deficient patients had more severe infections, as well as higher levels of CRP. The researchers explained that these outcomes are consistent with the observation that vitamin D is crucial for fighting inflammation and boosting immune response to infection.
Therefore, it makes sense that COVID-19 patients with sufficient vitamin D had less severe infections, clinical outcomes and immune reactions like a cytokine storm. (Related: Coronavirus hijacks immune cells to create cytokine storms, says new study.)
Taken together, these findings suggest that vitamin D sufficiency improves immune function among COVID-19 patients. Vitamin D's beneficial effect on the immune system may also reduce the risk of coronavirus infection in the first place.
Read more articles about the many health benefits of vitamin D at VitaminD.news.