Zinc is a very important mineral that is needed for hundreds of processes within the body, and when it is deficient, immunity and blood sugar control, among other things, can be compromised. As the best sources are seafood, which most people eat infrequently, it is often a good idea to supplement, but it is important to do so carefully. Relatively few people know that over-supplementing zinc can, in some cases, lead to copper deficiency over time, whose symptoms can be difficult to recognize.
How can zinc cause copper deficiency?
Consuming more zinc than your body needs triggers a mechanism that limits the absorption of zinc from the gut. However, our bodies do this by increasing the production of a substance that binds zinc in the intestinal tract, allowing it to be excreted later.
Unfortunately, this same substance does not only bind zinc. Copper also binds to it with a strong affinity so that even if we don't have an excess of copper, too much of it will be excreted, which can lead to copper deficiency.
How much zinc is too much?
The recommended intake of zinc from health organizations is around 10 mg per day, while the maximum recommended amount from supplements is 40 mg per day.
Although much research has found zinc supplementation to be beneficial for a variety of problems, it is probably really advisable to be careful with doses above 40-50 mg per day, especially if one is using it alone without supplementing with copper.
In a study published in 2015, 70 cases were collected where high-dose zinc supplementation was recommended for various problems. (1) The average dose used was 90-135 mg of zinc per day, which was already sufficient to cause copper deficiency.
In 9% of cases, the copper deficiency became symptomatic, although it is important to note that as this risky side-effect of zinc supplementation was not known, almost no one had their copper levels tested. In general, copper deficiency is very rarely identified as a potential source of danger, though it can lead to anemia and even permanent neurological damage. (2)
What’s the solution?
A relatively large number of zinc supplements contain 50 mg of zinc, and it is possible to consume more than this per day. 15 mg per day is enough for almost anyone to get enough zinc from their diet.
In addition, it is advisable to supplement with 1 mg of copper per day since, like zinc, higher amounts of it are found in foods that most people rarely eat.
Higher doses of zinc supplementation should only be used for short periods, e.g. in the case of illness, to ensure that it does not cause long-term problems.
- Duncan A, Yacoubian C, Watson N, Morrison I. The risk of copper deficiency in patients prescribed zinc supplements. J Clin Pathol. 2015 Sep;68(9):723-5. doi: 10.1136/jclinpath-2014-202837. Epub 2015 Jun 17. PMID: 26085547.
- Halfdanarson TR, Kumar N, Li CY, Phyliky RL, Hogan WJ. Hematological manifestations of copper deficiency: a retrospective review. Eur J Haematol. 2008 Jun;80(6):523-31. doi: 10.1111/j.1600-0609.2008.01050.x. Epub 2008 Feb 12. PMID: 18284630.