The relationship between copper, iron and zinc demonstrates the complexity of mineral absorption. Some minerals enhance absorption of other minerals, while some inhibit absorption. Some mineral pairs are actually mutual inhibitors -- each preventing the other from fulfilling its absorption potential.
Copper
Rather than copper causing a deficiency in either iron or zinc, iron and zinc both tend to inhibit absorption of copper. Therefore, foods high in copper -- such as beef liver and pecans -- do not have potential to cause a deficiency in either iron or zinc. The Recommended Dietary Allowance for adults is 900 micrograms per day.
Iron
In addition to inhibiting absorption of copper, iron also interferes with zinc absorption. In fact, iron and zinc are mutual inhibitors. Foods high in iron -- including beef liver, green vegetables and blackstrap molasses -- have potential to interfere with copper and zinc absorption when iron intake is above the Recommended Dietary Allowance of 8 mg to 18 mg per day for adults.
Zinc
Zinc inhibits absorption of both copper and iron. The Recommended Dietary Allowance of zinc is 8 g per day for adult women and 11 g per day for adult men. Foods high in zinc include beef liver, poultry, oysters and wheat germ.
Supplements
A well rounded diet that includes a variety of foods instead of the same foods every day is unlikely to cause an excess or deficiency of any minerals. However, because of the complex relationships of absorption and inhibition between various minerals -- including, but not limited to copper, iron and zinc -- exercise caution if you choose to take supplements. Avoid supplements that provide more than 100 percent of the daily requirements of minerals to minimize your risk of interfering with the absorption of other minerals. Check with your doctor before taking supplements if you have health problems or take other medicines, to avoid problems with interaction.
References
- "Advanced Nutrition and Human Metabolism: Third Edition"; James L. Groff and Sareen S. Gropper; 2000
- "Krause's Food and Nutrition Therapy: 12th Edition"; L. Kathleen Mahan and Sylvia Escott-Stump; 2008
- USDA National Agricultural Library; Dietary Reference Intakes
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