Zinc is an essential mineral that can be found most commonly in meat, eggs and vegetables. It is used to build numerous proteins, and plays a role in brain function, the immune system, antioxidant enzymes and more. It has been estimated that around 10% of the US population may be zinc deficient, and zinc deficiency has been linked to an impaired immune response, mental lethargy, depression and skin abnormalities.
Zinc appears to be important to immune system function. Zinc deficiency can impair the production of immune signalling molecules, which are restored upon supplementation. Zinc deficiency is also linked to reduced antibody production and T cell numbers.
These effects on the immune system seem to translate to an observable impact on the rate and duration of pathogenic infections. A meta-analysis of 15 trials including 1360 people found that zinc shortened the duration and severity of the common cold when taken within 24 hours of onset, and reduces the incidence of the illness when supplemented for 5 months. Zinc has also been found to inhibit the activity of various viruses including coronaviruses, and could possibly provide some defence against COVID-19.
Another meta-analysis suggested that zinc deficiency is associated with autoimmunity, which zinc supplementation could potentially protect against.
In addition to its effects on the immune system, zinc may have a wide range of other benefits. Meta-analyses suggest that zinc supplementation can lower blood sugar, reduce systolic blood pressure, and may also have antidepressant effects on its own or in conjunction with conventional antidepressant drugs.
Zinc is likely to be safe in doses under 40mg a day. Supplementation with more than this may be unsafe, especially for prolonged periods of time (because higher doses may reduce the absorption of copper by the body).
Zinc Deficiency in Human Subjects: https://pubmed.ncbi.nlm.nih.gov/6361778/
Zinc and Skin Disorders: doi: 10.3390/nu10020199
The Emerging Role for Zinc in Depression and Psychosis: doi: 10.3389/fphar.2017.00414
Zinc May Regulate Serum Leptin Concentrations in Humans: DOI: 10.1080/07315724.1998.10718758
The Dynamic Link between the Integrity of the Immune System and Zinc Status: https://doi.org/10.1093/jn/130.5.1399S
Zinc for the Common Cold: DOI: 10.1002/14651858.CD001364.pub3
Zinc Deficiency and Immune Function: DOI: 10.1146/annurev.nu.10.070190.002215
Zinc Status and Autoimmunity: A Systematic Review and Meta-Analysis: doi: 10.3390/nu10010068
Potential Role of Zinc Supplementation in Prophylaxis and Treatment of COVID-19: doi: 10.1016/j.mehy.2020.109848
The effect of zinc supplementation on blood pressure: a systematic review and dose–response meta-analysis of randomized-controlled trials: https://link.springer.com/article/10.1007/s00394-020-02204-5
Zinc Supplementation Improves Glycemic Control for Diabetes Prevention and Management: A Systematic Review and Meta-Analysis of Randomized Controlled Trials: DOI: 10.1093/ajcn/nqz041
The Efficacy of Zinc Supplementation in Depression: Systematic Review of Randomised Controlled Trials: DOI: 10.1016/j.jad.2011.06.022
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