Zinc and copper are both essential trace minerals required for human health. The ability of the two minerals to antagonise the absorption of one another has been demonstrated in the nutritional literature. This likely relates to common transport and storage routes within enterocytes, although antagonism within the tissues of the body is also possible. Many of the studies investigating this antagonisms have used unrealistically high intakes of copper and zinc. For example pharmacological doses of zinc are known to reduce serum ceruloplasmin in animals and in humans and may also have an effect on the levels of the important antioxidant enzyme copper-zinc superoxide dismutase in tissues. This last point is interesting because copper-zinc superoxide dismutase appear to be dependent of the copper status of the individual, but not the zinc status. However, the ability of the minerals to antagonise each other’s absorption at lower more dietary relevant concentrations is more controversial.
One study sought to answer questions about the effects of moderate zinc intakes on the copper status of healthy individuals using 50 mg per day zinc supplements as zinc gluconate for 6 weeks1. The authors measured the changes to the copper-metalloenzymes, the plasma ceruloplasmin as well as erythrocyte copper-zinc superoxide dismutase in order to assess the effects of the zinc supplementation. The zinc supplements had no effect on the plasma ceruloplasmin at any time point throughout the six weeks study. The zinc supplements did decrease the activity of the antioxidant enzyme copper-zinc superoxide dismutase in erythrocytes. However this took six weeks for changes to occur. This suggests that high intakes of zinc are able to cause gradual reductions in the activity of the superoxide dismutase enzyme that is reliant of adequate copper status. However, it is not clear from these results if the addition of higher intakes of copper to the subject’s diet may have prevented this decrease.