Table 4.

Mechanisms of the influence of other nutrients on zinc metabolism.

Nutrient	Mechanism
Proteins [64,65,66,67,68]	Protein is a major source of zinc, thus increased protein intake results in increased zinc intake High amounts of protein in enteral nutrition improve zinc absorption Casein in cow milk reduces zinc absorption
Lipids [69]	Fecal zinc increases in subjects with steatorrhea Medium-chain triglycerides improve zinc absorption
Copper [70]	Slight increase in copper intake does not interfere with zinc absorption if zinc intake is satisfactory. The effects of increased copper intake in subjects with low intake of zinc still remain to be defined.
Iron [71]	Iron administered at high doses (i.e., iron-zinc ratio of 25:1 molar) reduce zinc absorption. Duration of iron supplementation does not affect zinc status
Vitamin A [72]	Severe vitamin A deficiency may reduce absorption and lymphatic transport of zinc by altering synthesis of zinc-dependent protein
Folic acid [73]	Supplementation with folate may impair zinc absorption by insoluble chelate formation