Among patients with iron deficiency anemia (IDA), including vitamin C with oral iron supplementation does not appear to improve results compared with oral iron supplementation alone, according to research published in JAMA Network Open.

IDA may affect up to 30% of the international population. While an iron-rich diet can treat many cases, oral iron supplementation is often required.

Vitamin C, which has been shown to improve iron absorption, nonetheless remains a controversial supplement in this setting. This is because, according to the authors of the present paper, whether vitamin C supplementation improves iron absorption in a patient’s overall diet, rather than in single-meal instances, is unestablished. For this single-center randomized clinical trial ( Identifier: NCT02631668), researchers evaluated whether vitamin C supplementation is necessary for patients with IDA receiving oral iron supplements.

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Of 530 patients assessed for eligibility, 440 were randomly assigned to receive oral iron tablets with vitamin C supplementation (220 patients) or oral iron tablets only (220 patients); all patients were included in the primary analysis.

At baseline, patients in the vitamin C and oral iron supplement–only group had average ages of 38.0 and 39.6 years, respectively; 215 (97.7%) and 211 (95.9%) were women, and 201 (91.4%) and 200 (90.9%) had mild or moderate IDA, respectively. Baseline hemoglobin levels were 8.76 g/dL in the vitamin C group and 8.82 g/dL in the iron-only group.

After 2 weeks, the mean change in hemoglobin levels was 2.00 g/dL in the vitamin C group vs 1.84 g/dL in the iron-only group, representing a between-group difference of 0.16 g/dL; this met the study’s pre-established criteria for equivalence. Serum ferritin level changes from baseline to 8 weeks had a between-group difference of 1.27 (P =.21).

Adverse events also occurred at similar rates (46 in the vitamin C group vs 45 in the iron-only group; P =.82).

“The findings of this equivalence [randomized clinical trial] demonstrate that in patients with IDA, taking oral iron alone was equivalent to taking oral iron supplemented with vitamin C in improving hemoglobin level and iron stores,” the authors wrote. “Our results suggest that vitamin C is not essential for patients with IDA.”


Li N, Zhao G, Wu W, et al. The efficacy and safety of vitamin C for iron supplementation in adult patients with iron deficiency anemia: a randomized clinical trial. JAMA Netw Open. 2020;3(11):e2023644. doi:10.1001/jamanetworkopen.2020.23644