Effect of Recommended Dietary Intake versus Higher Doses of Supplemental Zinc on Iron and Copper Deficiency Anemia Among Patients with Chronic Kidney Diseases, A Double-Blinded, Randomized Clinical Trial

Background: Complex interplays happen in absorption and function of iron, zinc and copper. Both zinc deficiency and excess may lead to anemia. In Iran, commonly available supplements for chronic kidney disease (CKD) patients contain 25 mg-zinc (Zn). This study compared 25 mg versus 7.5 mg dose of zinc in anemia of CKD patients, the latter dose approximates to recommended dietary intake (RDI) of zinc. Methods: In this double-blinded clinical trial, 51 non-dialysis CKD patients were randomized to continue previous formulation (25 mg-Zn group) or change to a new preparation (7.5 mg-Zn group) for three months. Blood counts and serum iron, zinc and copper status were compared between and within the groups. Results: At the end of the study, serum copper and ceruloplasmin concentrations were significantly higher in 7.5 mg-Zn group compared with those in 25 mg-Zn arm (115.04± 23.05 vs. 102.48±14.98 µg/dL; P= 0.02 and 29.97±7.94 vs. 25.42±4.23 mg/dL; P= 0.01, respectively). Serum zinc levels did not differ between two groups (76.73±15.35 vs. 77.68±18.07 µg/dL for 7.5 mg-Zn and 25 mg-Zn groups, respectively; P= 0.84). After three months, patients in 7.5 mg-Zn group experienced increase in their Hb (11.11±1.17 vs. 10.72±1.03 g/dL; P= 0.04), HCT (35.28± 4.01 vs. 33.96± 3.74%; P= 0.03), MCV (86.30 (81.40-90.82) vs. 86.00 (80.35-88.77) ¦L; P= 0.01) and ferritin (202.60 (79.29-298.97) vs. 129.07 (42.25-225.87) ng/mL; P<0.001) compared to their baseline values. Conclusion: Reducing zinc content to its RDI value in supplement for CKD patients led to increased serum copper and ceruloplasmin concentrations. Moreover, patients who switched to RDI zinc-containing formula experienced a significant rise in blood hemoglobin. hematocrit, mean corpuscular volume (MCV), and ferritin concentration.