Copper, iron, zinc, and manganese in dietary supplements, infant formulas, and ready-to-eat breakfast cereals.

High intakes of iron, zinc, or manganese can interfere with copper absorption. Thus, the purpose of this study was to determine whether the amounts and chemical forms of iron, zinc, manganese, and copper added to food products and nutritional supplements might pose a threat to copper status. More than 25% of the vitamin and mineral supplements examined contained no copper, 40% contained the poorly absorbed cupric oxide, and < 30% contained a highly bioavailable form of copper such as cupric sulfate or cupric chloride. Nearly 40% of the prenatal supplements examined contained both iron and zinc without a nutritionally significant amount of copper. More than 80% of the infant formulas examined had ratios of iron to copper exceeding 20:1, which is higher than the recommended ratios of 10-17:1. None of the 40 ready-to-eat breakfast cereals examined were fortified with copper or manganese although 50% of these cereals contained > or = 25% of the reference daily intake for both iron and zinc. Copper availability could be improved by reformulation of several food products and supplements.