Low zinc, vitamin D levels may predict susceptibility to COVID-19

Patients with COVID-19 show very low levels of 25-hydroxyvitamin D and zinc, regardless of age, sex, and comorbidities, reports a study. Vitamin D and zinc deficiency appears to be relevant factors in identifying individuals who are susceptible to SARS-CoV-2 infection.

“Therefore, we recommend the diagnosis and treatment of individuals with low serum 25-hydroxyvitamin D and zinc levels,” said the researchers, led by Esmat Ghanei and Moein Baghani, both from Shahid Beheshti University of Medical Sciences, Tehran, Iran.

This single-centre case-control study was conducted from 20 March 2020 to 20 January 2021. The case group (n=90) included all patients diagnosed with COVID-19 based on a positive nasopharyngeal swab polymerase chain reaction (PCR) test, while the control group (n=95) involved those referred for routine checkups who had a negative COVID-19 PCR test.

The researchers then recorded the patients’ age, sex, marital and educational status, comorbidities, and serum 25-hydroxyvitamin D and zinc levels.

Vitamin D levels >20 ng/ml were seen in 58 COVID-19 patients and 72 controls (64 percent vs 76 percent; p=0.09). The case group had significantly lower median 25-hydroxyvitamin D levels than the control arm (26 vs 38 ng/ml; p<0.01). [Eur J Clin Nutr 2022;76:1297-1302]

Median zinc levels were 56 and 110 mcg/dL in the case and control groups, respectively (p<0.01). No significant difference was noted in zinc and vitamin D levels between COVID-19 patients with and without comorbidities (p>0.05).

Susceptibility to SARS-CoV-2 infection could be predicted by serum 25-hydroxyvitamin D levels <25.2 ng/ml (sensitivity, 81 percent; specificity, 48 percent) or zinc levels <86.3 mcg/dL (sensitivity, 93 percent; specificity, 92 percent).

These findings are consistent with those from a recent study by Hurst and colleagues, which showed a higher frequency of vitamin D insufficiency/deficiency among hospitalized COVID-19 patients. [BMJ 2021;11:e055435]

“The potential roles of 25-hydroxyvitamin D in reducing the risk for COVID-19 include decreasing the replication and viability of SARS-CoV-2 through induction of antimicrobial peptides and binding to the host cell surface receptors, and decreasing the cytokine storm through promoting the body’s ability to reduce the production of inflammatory cytokines,” the researchers said. [Endocr Pract 2021;27:1266-1228]

A literature review also revealed that vitamin D and zinc deficiency could compromise the immune system, making individuals more prone to viral infections and increasing the odds of a poor disease prognosis. [Front Nutr 2020;7:295]

“However, it is not yet clear whether 25-hydroxyvitamin D deficiency leads to severe COVID-19 disease or 25-hydroxyvitamin D is reduced as a result of severe disease, potentially due to its consumption,” the researchers said. [Nutrients 2021;13:740]

Of note, another study demonstrated that oral 25-hydroxyvitamin D could enhance the immune function in COVID-19 patients with 25-hydroxyvitamin D levels <30 ng/ml by increasing blood lymphocyte percentage. [Endocr Pract 2021;27:1242-1251]

“Although lower levels of 25-hydroxyvitamin D may make individuals prone to COVID-19 affliction, the opposite may not be true,” the researchers said. “Respiratory diseases can reduce 25-hydroxyvitamin D levels.”