Ferrous sulfate and gut bacteria in Cambodian women
What it found
In 144 nonpregnant Cambodian women, 12 weeks of ferrous sulfate or ferrous bisglycinate did not change the amount of Group B Streptococcus DNA in stool compared with placebo.
The authors say the iron supplements did not increase this marker of gut colonisation.
What they found
Studies in people
Group B Streptococcus marker
The amount of the cfb gene in stool did not change from the start to the end of the study in any of the three groups. There was also no difference between the groups after 12 weeks.
Regional differences
Women from Srayov district had lower levels of the cfb gene at both the start and end of the study than women from Prey Kuy or Tboung Krapeu. This suggests that something in the environment or behaviour may affect Group B Streptococcus colonisation.
Iron status
Most women in the study already had enough iron. Only 6% had iron deficiency and 17% had anaemia at the start. After 12 weeks, iron deficiency was 0% in the ferrous sulfate and ferrous bisglycinate groups and 6% in the placebo group.
Adherence
About 62% of the women took at least 80% of their capsules over the 12 weeks.
What the authors conclude
“Oral iron supplementation for 12 wk did not increase cfb expression in this population of predominantly iron-replete Cambodian women, compared with placebo.”
Also in their conclusions
- They conclude that oral iron supplementation for 12 weeks did not increase cfb expression in this population of predominantly iron-replete Cambodian women, compared with placebo.
- They note that the observed geographic variation in cfb expression across districts suggests that environmental or behavioral factors may contribute to GBS colonization risk.
- They highlight the need to further investigate region-specific risk factors and provide a foundation for future research into GBS screening in Cambodia.
How it was done
The authors wanted to see whether extra iron that is not absorbed in the gut could encourage the growth of harmful bacteria such as Group B Streptococcus. They also wanted to compare two forms of iron supplements, ferrous sulfate and ferrous bisglycinate.
They studied 144 nonpregnant women aged 18 to 45 in Kampong Thom, Cambodia, who took either 18 mg iron as ferrous bisglycinate, 60 mg iron as ferrous sulfate, or a placebo for 12 weeks. Stool samples were collected before and after the 12 weeks and tested for a gene called cfb, which is a marker for Group B Streptococcus.
What it can’t tell you
- The stool test used cannot tell whether the Group B Streptococcus DNA came from live bacteria or just leftover DNA, and it may miss some strains that do not have the cfb gene.
- The study only collected stool samples twice, so it cannot show short-term changes in Group B Streptococcus colonisation.
- The study did not look at whether women had active infections or any health outcomes from Group B Streptococcus.
Who paid
- Conflicts
- Conflict of interest LXP received graduate student scholarships from CIHR and reports a relationship with Balchem Corp that includes: travel reimbursement. JAJF received graduate student scholarships from CIHR. CDK reports a relationship with Balchem Corp that includes: receiving grants. CDK is a Michael Smith Foundation for Health Research Scholar and a CIHR Canada Research Chair in Micronutrients and Human Health. CDK is an editor for The Journal of Nutrition and played no role in the journal’s evaluation of the manuscript. All other authors report no conflicts of interest.
- Authors work at
- The University of British Columbia, Canada; BC Children's Hospital and Women's Health Research Institutes, Canada
The paper
- Title
- Iron Supplementation with Ferrous Sulfate or Ferrous Bisglycinate for 12 Weeks Does Not Influence Group B Streptococcus Colonization in Cambodian Women: A Secondary Analysis of a Randomized Controlled Trial
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Cirigliano E, Saint A, Pei LX, et al (2025). Iron Supplementation with Ferrous Sulfate or Ferrous Bisglycinate for 12 Weeks Does Not Influence Group B Streptococcus Colonization in Cambodian Women: A Secondary Analysis of a Randomized Controlled Trial. The Journal of nutrition. doi:10.1016/j.tjnut.2025.10.014Free full textPubMed 41082982DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error