Many of you have been asking about zinc and its possible protective effects from COVID-19. Recently, there have been a series of observational studies from Spain, India, and Japan demonstrating that low zinc levels are associated with worse outcomes with COVID-19 infection. These studies were not randomized controlled trials demonstrating that giving zinc improved outcomes, rather they demonstrated that low levels were associated with worse outcomes. However, as we have discussed: association does not equal causation!
Earlier we saw a similar storyline with vitamin D, which I reviewed in an earlier blog (www.barryrotmanmd.com). Interestingly, since I wrote the blog in July 2020, a small, but well-designed, randomized controlled trial of vitamin D in hospitalized COVID-19 patients demonstrated a statistically significant reduction in progression of illness requiring ICU level of care. This study validated my advice that because vitamin D was very safe, it would be prudent to take it while awaiting better evidence of its efficacy.
Zinc presents a more complicated picture. Prior to COVID-19, there was already a large body of literature documenting zinc’s important role on the immune system, as well as anti-viral properties. However, zinc supplementation poses a much greater risk of side effects than does vitamin D. Zinc can cause nausea, vomiting, diarrhea, impaired appetite, as well as more serious side effects such as anemia and reduced white blood cell counts. Given the higher side effect risk, the level of evidence needs to be higher, in order to recommend taking zinc supplements “just to be safe.”
Furthermore, the number of people with low zinc levels in the United States is relatively low at around 15%. A regular, American diet does a good job of providing sufficient levels. Zinc can be found in meat, dairy products, nuts, and grains. Those with low levels may have food insecurity or illnesses with malabsorption, such as active inflammatory bowel disease or severe alcoholism. A strict vegan diet may also pose a risk. The NIH has a valuable fact sheet about zinc: https://ods.od.nih.gov/factsheets/Zinc-Consumer/.
If you believe you are at risk for low zinc, please let us know and we can arrange for a blood test to determine if you require zinc supplementation.
However, for everyone else, given adequate levels of dietary zinc, there is no benefit to zinc supplementation and only the risk of very unpleasant side effects.
Please contact me with any questions or concerns.
Barry Rotman, MD