Zinc is a trace element that plays a part in numerous biological processes within the human body. During the COVID-19 pandemic, there was considerable public interest in whether zinc could offer protection against the virus or help manage the illness. This interest stemmed from zinc’s known involvement in immune function and its potential antiviral properties. Understanding its general roles and specific implications for COVID-19 requires a closer look at the scientific evidence.
Zinc’s General Immune Function
Zinc is essential for immune system function, influencing both innate and adaptive immunity. It is involved in the development and function of various immune cells, including T-cells, natural killer (NK) cells, and macrophages. Zinc deficiency can impair these cells’ activities, such as phagocytosis, intracellular killing, and cytokine production, leading to a weakened immune response and increased susceptibility to infections.
Beyond its role in cell development, zinc also acts as an antioxidant, reducing oxidative stress within the body. Oxidative stress can contribute to chronic inflammation, which is linked to various illnesses. Zinc’s ability to stabilize cell membranes and regulate inflammatory proteins underscores its support for immune health.
Investigating Zinc’s Role in COVID-19
Zinc’s potential against COVID-19 was hypothesized to involve inhibiting viral replication and modulating inflammatory responses. Studies have shown that zinc can directly impede the activity of RNA-dependent RNA polymerase (RdRp), an enzyme that coronaviruses like SARS-CoV-2 use to replicate their genetic material. This could slow viral spread.
Zinc also has anti-inflammatory properties, influencing signaling pathways like NF-κB to regulate the body’s inflammatory response. Some research explored zinc ionophores, compounds that transport zinc into cells, to enhance its antiviral effects by increasing intracellular zinc. Some observational studies and meta-analyses suggested zinc supplementation might reduce in-hospital mortality in hospitalized COVID-19 patients, especially when combined with certain treatments. However, other studies found no significant improvement in severe COVID-19 events, such as the need for mechanical ventilation or acute kidney injury.
Dosage, Supplements, and Safety
The Recommended Dietary Allowance (RDA) for zinc varies by age and sex; for adults aged 19 and above, it is 11 mg for men and 8 mg for women. Pregnant and lactating individuals require slightly more, around 11-12 mg daily. Most people can obtain sufficient zinc through a balanced diet rich in foods like oysters, beef, poultry, legumes, nuts, seeds, and fortified cereals.
Zinc supplements are available in various forms, including zinc gluconate, zinc acetate, and zinc sulfate. Adhering to safe upper intake levels is important, as excessive zinc can lead to adverse effects. The Tolerable Upper Intake Level (UL) for zinc in healthy adults is 40 mg per day. Amounts above this level can cause side effects like nausea, vomiting, abdominal pain, diarrhea, headaches, and a metallic taste. Prolonged high doses can also interfere with copper absorption, potentially leading to copper deficiency and may affect iron absorption.
Official Recommendations
Major health organizations, including the World Health Organization (WHO), the National Institutes of Health (NIH), and the Centers for Disease Control and Prevention (CDC), generally do not recommend widespread zinc supplementation for COVID-19 prevention or treatment. They emphasize insufficient evidence for routine zinc supplementation, unless a confirmed deficiency exists.
Healthcare professionals advise against general supplementation without medical guidance. Instead, they reinforce the importance of a balanced diet for adequate nutrient intake and following established public health measures like vaccination, hand hygiene, and social distancing as primary strategies for managing COVID-19.