Extra zinc moved copper and iron blood tests the wrong way in toddlers
Pooling 39 studies at 3 to 70 mg of zinc a day, zinc worsened blood copper, ferritin, haemoglobin and the odds of anaemia in at least one subgroup. These are markers, not illnesses.
What the study found
Extra zinc moved copper and iron markers in under-threes
Pooling 39 studies at 3 to 70 mg of zinc a day, zinc worsened blood copper, ferritin, haemoglobin, haematocrit and the odds of anaemia in at least one subgroup. It left untouched the very copper enzyme the adult 40 mg ceiling was set on, which the authors flag as a gap, not an answer.
The caveat · Lab markers, not illness
Every outcome here is a laboratory marker rather than an illness, so this shows zinc moving numbers, not children coming to harm. The authors say outright that whether the findings matter clinically is unclear, and the certainty runs from very low to moderate. Each adverse finding held in at least one subgroup rather than across the board, so none of it describes a general effect of a stated dose.