Zinc Supplements: The Potential to Lower Iron (Ferritin) Levels Must Not Be Forgotten

Zinc supplements lower serum ferritin in some patients

Patients who use zinc supplements need to be aware of the delicate balance that exists between how the body absorbs iron and zinc. Long term use of zinc supplements without measuring zinc and iron and copper levels is not advisable. This is because chronic zinc consumption has the potential to lower iron and copper levels.  Zinc and iron complete with each other for intestinal absorption. In addition, increased zinc absorption has the potential to lead to increased exertion of copper. The net result is that chronic zinc use has the potential to lead to both low iron levels and low copper levels. 

In 2002, Carmen Donangelo and colleagues published a nice study in the Journal of Nutrition. The authors studied the effect of 6 weeks of zinc supplementation compared to 6 weeks of iron supplementation in young women with low ferritin levels (less than 20). The women were divided in two groups - 11 took zinc supplements and 12 took iron supplements.  In the iron-supplemented group, blood hemoglobin, plasma ferritin and the percentage of transferrin saturation increased but zinc indices did not change. In the zinc-supplemented group, plasma ferritin and the percentage of transferrin saturation decreased, whereas the plasma transferrin receptor and erythrocyte zinc protoprophyrin levels increased.  The authors concluded that the use of iron supplements in women with low ferritin levels improves iron indices with no effect on zinc status but that the use of zinc supplement improves zinc indices, but has the potential to reduce worsen iron deficiency.

This was a very nice study and serves as a helpful reminder that supplements should always be used in a rationale manner. If zinc supplements are going to be used in an ongoing manner, one should consider periodically measuring zinc, iron (and copper) levels. 

Reference

Donangelo C et al. Supplemental Zinc Lowers Measures of Iron Status in Young Women with Low Iron Reserves. The Journal of Nutrition, Volume 132, Issue 7, July 2002, Pages 1860–1864.