Oral ferrous sulphate supplementation has greater efficacy, but lower tolerance than iron (III)-hydroxide polymaltose complexes in exercising women with low iron stores

Abstract

Background & aims

Iron deficiency (ID) is a global health condition that predominately affects women. Although oral iron supplementation is an effective treatment strategy for this issue, gastrointestinal complaints are common, and if persistent, may lead to poor compliance. The efficacy of different iron formulations which claim to improve tolerance is unclear. This study assessed the efficacy and tolerability of ferrous sulphate (FS) and iron (III)-hydroxide polymaltose complex (IPC) supplementation in three different cohorts of women..

Methods

This study implemented a 12-week, single-blind, randomized controlled trial. Eligible participants had a serum ferritin concentration of <50 μg/L and met specific inclusion criteria to be enrolled to either the athlete, pre-menopausal or post-menopausal groups. Participants were randomized to receive FS (equivalent to 105 mg elemental iron) plus sodium ascorbate or IPC (equivalent to 100 mg elemental iron) daily. Venous blood samples were collected at baseline, 4-, 8- and 12-weeks of supplementation. A daily questionnaire was completed throughout the study period, documenting supplement tolerance (number and severity of symptoms), exercise load, menstrual characteristics, and supplement compliance.

Results

Fifty-seven participants completed the intervention with a compliance rate of 94.9 % [range: 74.8–100 %]. A significant interaction between supplement and time was evident for ferritin (p < 0.001), where FS increased after 12 weeks (+109 %; p < 0.001) but no change was evident in IPC (+7 %; p = 0.727). No differences were detected between cohorts (p > 0.05). The IPC group had a lower symptom rate compared to FS (28 % vs. 33 %; p < 0.001)..

Conclusions

FS was superior in repleting ferritin concentrations after 12 weeks compared with IPC; however, FS also resulted in a greater number and severity of GI symptoms than IPC. Our data shows FS is the superior iron formulation for ID treatment, however future research should continue to address how to improve FS tolerance.. This trial was registered at https://www.anzctr.org.au/Trial/Registration/TrialReview as ACTRN12623000529640.