https://onlinelibrary.wiley.com/doi/full/10.1002/ccr3.2987
I really should have written this before, but as is often the case, it kept getting displaced by other priority items on my schedule, until the urgency of it hits me in the middle of a busy clinic day.
With this prolonged COVID pandemic and a more contagious newcomer hitting just about every one, many prevention minded patients are trying to keep themselves healthy by increasing supplementation of certain nutrients associated with a better mucosal immune response. Zinc has become a very popular go-to in that regard, but there is a LOT of confusion and counterproductive practices surrounding its use, and more worrisome, some really bad potential side effects.
Zinc has some well documented benefits for upper respiratory viral protection, and in taste smell recovery. BUT MORE IS NOT BETTER. Zinc is one of many trace minerals that are absorbed and metabolized in a delicate relative balance. Zinc and copper in particular, will down regulate each other. It means that it you take a higher dose of zinc alone for a prolonged period of time, you will decrease copper, and copper is actually really important for many neurological and blood building functions. Copper deficiency can mimic iron deficiency anemia. This was a case I encountered earlier this week, and which prompted me to write this blog. One of our patients was dealing with a persistent anemia for months, elusive to diagnosis and treatment. She lives with high risk individuals and really wanted to limit her risk of bringing COVID home by taking a boosting supplement that contained 100 mg of zinc.
Higher doses of zinc alone would be along the line of more than 50 mg of daily zinc for more than 4 weeks, without balancing with other trace minerals. You would have to also look at other supplements taken daily along with zinc to estimate your total daily intake since many supplements will contain smaller amounts of zinc. In general 30 mg a day of zinc is not considered an issue in the long term, and that is why you will almost never see professional brands containing more than that amount in standalone zinc supplementation.