Can supplemental iron have a negative effect on the infant gut microbiota composition? Original paper

In this meta-analysis of randomized controlled trials, infants who were treated with iron-fortified food or iron supplements had a decreased population of Bifidobacteria in their gut microbiota.

The effect of iron supplements or iron-fortified food on the gut microbiota composition (i.e., beneficial vs. pathogenic bacteria) in infants.

A total of 156 infants (ages 0–6 months).

The infants were exclusively or predominantly breastfed at enrollment in 3 of the studies.

A meta-analysis of 4 randomized controlled trials was performed. The studies were conducted in Sweden (1 study), Kenya (1 study), Denver (1 study), and Canada (1study).

To conduct the meta-analysis the participants were divided into 2 groups:

• The iron group, which included infants who were treated with iron-fortified food (e.g., formula, cereal) or iron supplements
• The noniron group, which included infants who were given nonfortified food naturally containing iron (e.g., meat), a placebo, or food that did not contain iron

The Bifidobacteria population in the infants’ gut microbiota was reduced by 10.3% in the iron group and by 2.96% in the noniron group.

Although quantitative data on the microbiota analyses were reported by all studies, they did not use the same reporting methods. Additionally, the form and amount of iron that was administered differed between studies.

It’s also worth noting that data from the noniron group were primarily influenced by one study, which could affect the reliability of the results.