Should you take extra copper when taking high doses of zinc?
Anyone who takes more than 25 mg of elemental zinc per day over a prolonged period runs a real risk of copper deficiency, sometimes with serious consequences. Have your blood values checked and always discuss high zinc doses with your doctor.
Yes, if you take high doses of zinc, you need to keep an eye on your copper levels. Zinc and copper compete for the same absorption pathways in the gut wall. Taking a lot of zinc blocks copper absorption. This is not theoretical: at doses of 100 to 300 mg of zinc per day, anaemia and a deficiency of white blood cells (neutropenia) caused by copper deficiency have been demonstrably established. That is well above the recommended daily amount, but some supplements already come close.
The European Food Safety Authority uses 25 mg of elemental zinc per day as the safe upper limit; in the United States the limit is 40 mg per day. Using zinc above those limits over a prolonged period increases the risk of copper deficiency. What counts on the label is the amount of elemental zinc in milligrams, not the weight of the salt. Whether that is zinc sulphate, zinc gluconate or zinc oxide makes no difference for this risk: what matters is your total amount of elemental zinc per day.
Copper deficiency is often not recognised in practice. Scottish laboratory research showed that in 7 of 14 confirmed cases the diagnosis had not yet been made. The consequences can be serious: anaemia and neutropenia are fully reversible within four to twelve weeks after copper supplementation, but neurological damage, such as injury to the spinal cord, can only be partially reversed. One case report describes copper deficiency after ten months of excessive zinc use, in which stopping zinc and taking oral copper initially helped insufficiently, because too much zinc was still present in the body.
If you take more than 25 mg of zinc daily, it is sensible to have your copper and blood values checked. Adding extra copper is not always the solution while a large amount of zinc is still present, because competition in the gut continues even then. In research, people with copper deficiency received copper gluconate or copper sulphate orally, or intravenously in serious cases. Always discuss prolonged use of high zinc doses with your doctor, so that your blood values can be monitored regularly.
Based on reviews, a Scottish laboratory study and case reports. There are no randomised trials involving deliberate copper deficiency (for ethical reasons), but the mechanism and the clinical cases are well documented.
Which form of zinc is best to take?
Zinc picolinate and zinc histidine have the strongest independent evidence for good absorption, but all comparative studies are small. Avoid large portions of grains around the time of intake, as phytate substantially blocks absorption.
Can you take too much magnesium?
Yes, too much magnesium can be dangerous, although serious toxicity through ordinary supplements is rare in people with healthy kidneys. With kidney problems or the use of intravenous magnesium, medical supervision is genuinely necessary.
Does taking iron help, or is it actually a risk?
Taking iron clearly helps if you have a deficiency or anaemia, but is pointless and potentially risky if that is not the case. Have your iron levels checked before starting supplements.
Which form of magnesium is best to take?
Magnesium citrate has the strongest evidence for absorption into the body. Magnesium oxide, the cheapest option, demonstrably performs the worst and is best avoided.
Is too much zinc harmful?
Too much zinc is certainly harmful: as an adult, stay below 25 mg of elemental zinc per day (EFSA limit) and be cautious with high-dose zinc supplements, because even moderate over-supplementation can disrupt copper balance.
Is zinc beneficial for my immune system?
Zinc is useful for your immune system if you have a deficiency or belong to a risk group, such as older adults or severely malnourished people. For colds, up to 30 mg of elemental zinc per day may shorten symptoms, but high doses are more likely to be harmful than beneficial.