Background: Routine zinc supplementation is a potential intervention for the prevention of acute lower respiratory infections in developing countries. However discrepant findings from recent randomized trials remain unexplained.
Methods: Single centre, single arm, prospective non-randomized, open label interventional study, of effect of zinc supplementation in zinc deficient children aged 6 months to 5 years. 465 healthy children aged 6 months to 5 years were enrolled in the study. The primary outcome was the prevalence of serum zinc deficiency. Children having zinc deficiency were recruited for the study of effect of oral administration of zinc 20 mg for 2 weeks. The secondary outcomes were incidence and duration of acute upper respiratory and acute lower respiratory infections per child-year and side effects after giving zinc therapy.
Results: There was significant difference in mid arm circumference in between zinc deficient and non-zinc deficient groups (p < 0.001). Also the number of episodes of acute upper respiratory infections (AURI) and mean duration of AURI and acute lower respiratory infections (ALRI) was significantly different in the two groups (p < 0.001). There was no significant difference in ALRI episodes in two groups. After zinc supplementation in zinc deficient children, there was significant decrease in the number of episodes and mean duration of AURI (p < 0.001) and ALRI (p < 0.001) in six months after supplementation as compared to preceding six months before supplementation.
Conclusion: This study sheds light on the efficacy of short course prophylactic zinc supplementation in reducing the burden of ARI among zinc deficient children. Future studies should assess the effectiveness of delivering prophylactic zinc supplementation at scale, comparing the feasibility and cost benefit of short course and continuous regimens.
Clinical Trial Number: As it was a Non Randomized observational single arm study, study was not registered. Only RCT needs to be registered.
Funding Statement: This study was funded by All India Institute of Medical Sciences (AIIMS), Manuscript Jodhpur, India, as a part of Intramural project conducted in the department of Pediatrics, AIIMS Jodhpur.
Declaration of Interests: We declare no competing interests.
Ethics Approval Statement: The study was approved by Institutional Ethics committee of All India Institute of Medical Sciences, Jodhpur, India. The study was conducted in accordance with ICH-GCP and other applicable regulatory guidelines.
This 2020 review highlighted earlier clinical data on zinc:
“Zinc is known to modulate antiviral and antibacterial immunity and regulate inflammatory response.
Zinc possesses anti-inflammatory activity by inhibiting NF-κB signaling and modulation of regulatory T-cell functions.
The most critical role of zinc is demonstrated for the immune system.
Zinc regulates proliferation, differentiation, maturation, and functioning of leukocytes and lymphocytes.
Alteration of zinc status significantly affects immune response resulting in increased susceptibility to inflammatory and infectious diseases including acquired immune deficiency syndrome, measles, malaria, tuberculosis, and pneumonia. Zinc status is associated with the prevalence of respiratory tract infections in children and adults.
In view of the high prevalence of zinc deficiency worldwide (up to 17%), its impact on population health is considered as a significant issue. Certain groups of people, including infants, especially preterm ones, and elderly, are considered to be at high risk of zinc deficiency and its adverse effects.
Zinc was shown to have a significant impact on viral infections through modulation of viral particle entry, fusion, replication, viral protein translation and further release for a number of viruses including those involved in respiratory system pathology. Increasing intracellular Zn levels through application of Zn ionophores significantly alters replication of picornavirus, the leading cause of common cold.
The results of systematic analysis confirmed the efficiency of intake of at least 75 mg/day Zn in reduction of pneumonia symptom duration but not severity, with the response being more pronounced in adults than in children.”
BACKGROUND: Airway epithelium is the first line of defense against a variety of exposures. Inflammatory processes, hyperresponsiveness and zinc deficiency cause epithelial damage. Zinc is involved in apoptosis and microtubule formation. However, its role in the integrity of bronchial mucosa and cilia is unclear.
METHODS: To assess the effect of zinc on the integrity of the bronchial epithelium, 24 male Rattus norvegicus strain Wistar rats were randomized into four experimental groups: normal zinc diet group without zinc supplementation, normal zinc diet group with 60 ppm zinc supplementation, zinc deficient diet group without zinc supplementation, and zinc deficient diet group with 120 ppm zinc supplementation. Bronchial mucosal integrity was measured with the number of epithelial cells, and the number and length of cilia.
RESULTS: Number of cell in normal zinc diet group was 8.8±1.82, while it was only 8.1±1.08 in zinc deficient diet group (p<0.001). Number of cilia per cell was 4.6±1.08 in normal zinc diet group, compared to 4.0±0.79 in zinc deficient diet group (p<0.001). Ciliary length also differ by 7.68±0.66 μm in normal zinc diet group and only 5.16±0.91 μm in zinc deficient diet group (p<0.001).
CONCLUSION: Zinc supplementation of the normal zinc diet group affected the length of bronchial cilia. Zinc supplementation of the zinc deficient diet group affected the integrity of the bronchial epithelium, which was shown by the number and length of cilia, and the number of epithelial cells.
In view of the emerging COVID‑19 pandemic caused by SARS‑CoV‑2 virus, the search for potential protective and therapeutic antiviral strategies is of particular and urgent interest. Zinc is known to modulate antiviral and antibacterial immunity and regulate inflammatory response. Despite the lack of clinical data, certain indications suggest that modulation of zinc status may be beneficial in COVID‑19. In vitro experiments demonstrate that Zn2+ possesses antiviral activity through inhibition of SARS‑CoV RNA polymerase. This effect may underlie therapeutic efficiency of chloroquine known to act as zinc ionophore. Indirect evidence also indicates that Zn2+ may decrease the activity of angiotensin‑converting enzyme 2 (ACE2), known to be the receptor for SARS‑CoV‑2. Improved antiviral immunity by zinc may also occur through up‑regulation of interferon α production and increasing its antiviral activity. Zinc possesses anti‑inflammatory activity by inhibiting NF‑κB signaling and modulation of regulatory T‑cell functions that may limit the cytokine storm in COVID‑19. Improved Zn status may also reduce the risk of bacterial co‑infection by improving mucociliary clearance and barrier function of the respiratory epithelium, as well as direct antibacterial effects against S. pneumoniae. Zinc status is also tightly associated with risk factors for severe COVID‑19 including ageing, immune deficiency, obesity, diabetes, and atherosclerosis, since these are known risk groups for zinc deficiency. Therefore, Zn may possess protective effect as preventive and adjuvant therapy of COVID‑19 through reducing inflammation, improvement of mucociliary clearance, prevention of ventilator‑induced lung injury, modulation of antiviral and antibacterial immunity. However, further clinical and experimental studies are required.