“Since zinc is non-toxic, non-expansive, readily available, and plays an important role as an immune modulator, its application in COVID-19 may provide a clinical, cost-effective benefit to facilitate a meaningful recovery with a better prognosis,” write scientists from Wayne State University, USA in Antioxidants.
Clinical evidence suggests zinc is effective at reducing infection severity in adults and incidence in children and elderly subjects through down-regulation of inflammatory cytokines/chemokines and oxidative stress markers, they explain.
Zinc deficiency
Zinc deficiency is reported to affect about 30 % of the world’s population. The human body cannot make it, so it has to come from our diet.
It is estimated that more than 1 in 6 people globally are deficient in zinc and that around 1 in every 58 deaths in children under five is related to zinc deficiency.
The potential immune health benefits of zinc are linked to “strong support” for treating the upper respiratory infections, notably the common cold, due to its anti-viral activity.
A 2017 meta-analysis published in the Royal Society of Medicine’s JRSM Open found that zinc lozenges providing 75 mg per day of elemental zinc may shorten the duration of the common cold by about 33%, but the zinc must be taken within 24 hours of the onset of the infection. Similar conclusions were drawn in a 2011 review by the prestigious Cochrane Collaboration that covered zinc syrup, lozenges or tablets.
Zinc plays an essential preventative role in modulating cellular immune responses, including natural killer cells, T lymphocytes and B lymphocytes, and has been reported to determine severity of COVID-19.
Depleted levels are considered to be 89 μg/dL of serum zinc or less and increase the prevalence of human viruses, bacterial fungus, and parasites, with the elderly particularly vulnerable.
“Our early experimental studies revealed that dietary restriction-induced zinc depletion reduced the relative level of CD8+/CD73+ T lymphocytes in volunteer subjects,” said the Wayne State researchers.
“Furthermore, zinc deficiency causes thymic atrophy along with the down-regulation of thymulin, a zinc sensitive thymic hormone for the regulation of T cell proliferation and differentiation as well as NK cell activation.”
Emerging studies also indicate anti-inflammatory and antioxidant mechanisms that contributed to fewer infections and reduced sickle cell anaemia (SCD) in patients.
Manage viral infections
Viral zinc homeostasis is crucial to manage viral infections, depending on the context of the virus, the authors explain.
“The passive release of bound zinc from the viral zinc finger or zinc containing proteins, termed zinc ejection, has been reported to be associated with the modulation of viral activities. Zinc ejection is caused by the binding of some compounds to viral zinc finger proteins, resulting in destabilization of these zinc finger proteins.”
Increasing zinc intake through supplementation may reverse these effects, they maintain. Remedial activity may be further enhanced with the addition of zinc ionophore compounds, such as hydroxychloroquine (HCQ), they said, that bolster the binding process to viral enzymes and inhibit viral activity in novel coronaviruses.
Combined treatment with HCQ, azithromycin, and zinc, in one trial, triggered a decrease in hospital admissions (2.8% vs. 15.4%) and deaths (0.7% vs. 3.4%) in COVID-19 patients, although the exact mechanism of “synergic effect” is still not fully understood, the authors wrote.
Toxic levels
High dose zinc can lead to gastrointestinal problems (abdominal pain, nausea, vomiting), but these are generally well-tolerated. Toxic levels may also impair immunity, similar to the effect of zinc deficiency on immunity.
“Therefore, zinc homeostasis seems to be critical for the maintenance of normal immunity in the body,” the authors commented.
However, they add that data from 18 clinical trials demonstrated zinc efficacy in a wide range of doses and treatment periods and therefore suggest its application as a potent anti-viral agent, along with anti-inflammatory and antioxidant properties, “may provide a meaningful clinical benefit for the treatment of COVID-19”.
Source: Antioxidants
Published online, September 21, 2022: http://doi.org/10.3390/antiox11101862
‘The Mechanisms of Zinc Action as a Potent Anti-Viral Agent: The Clinical Therapeutic Implication in COVID-19’
Authors: A.S. Prasad, et al.