Are iron-folate supplements harmful?

Zinc absorption during pregnancy was measured before and 24 h after 2 wk of daily, oral, iron-folate supplements. Absorption was reduced 24 h after iron-folate, which suggests a mucosal rather than a luminal effect. Also, zinc absorption in 10 healthy volunteers was reduced by folate supplements alone. Therefore, routine iron and folate supplementation may both have deleterious effects on zinc metabolism, especially during pregnancy when iron-folate supplements are often prescribed despite adequate dietary intakes of iron and folate but not of zinc.