Synbiotic Supplementation Improves Response to Iron Supplementation in Female Athletes during Training

J Diet Suppl. 2022;19(3):366-380. doi: 10.1080/19390211.2021.1887423. Epub 2021 Feb 22.


Objective: Iron deficiency (ID) affects ∼30% of female athletes, and its consequences are highly relevant to athletic performance. Poor iron (Fe) uptake remains a major factor in the development of ID. While studies suggest that consumption of either prebiotics or probiotics may improve Fe uptake, consumption of synbiotics has not been well-studied. The main objective of this study was to determine the effects of synbiotic supplementation on the Fe status of female athletes during Fe repletion.

Methods: The Fe status of 32 female athletes was screened early in the season. Twenty eligible athletes (hemoglobin:12.3 ± 0.9g/dL; serum ferritin, sFer:18.1 ± 9.2 µg/L) were randomized to receive either a daily synbiotic supplement (5 g prebiotic fiber + 8 billion colony forming units, CFU probiotic B. lactis) or placebo, along with Fe supplementation (140 mg ferrous sulfate, FeSO4/d) for 8 weeks using a double-blind design. Fe status was assessed again at mid-point and after the trial.

Results: Nineteen athletes (n = 9 supplement, 10 placebo) completed the trial and there were no differences in compliance or GI symptoms reported between groups. After controlling for baseline Fe status, regression analyses revealed improvements in log sFer in the supplement group after both 4 and 8 weeks (p = 0.01 and p = 0.05, respectively), compared to placebo.

Conclusions: Synbiotic supplementation along with FeSO4 improved athletes' Fe status over 8 weeks. This data is essential to advancing our understanding of how dietary and supplemental Fe uptake in active women can be enhanced by synbiotic supplementation, as well as by foods containing pre- and probiotics.

Keywords: Serum ferritin; athletes; clinical trial; iron; iron deficiency; prebiotic; probiotic; synbiotic.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Dietary Supplements
  • Double-Blind Method
  • Female
  • Hemoglobins
  • Humans
  • Iron
  • Male
  • Prebiotics
  • Probiotics*
  • Synbiotics*


  • Hemoglobins
  • Prebiotics
  • Iron