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Low-dose iron supplementation given to breastfed infants did not improve early development or iron status, a randomized controlled trial found.

Among 221 infants ages 4 to 9 months, randomization to iron supplements rather than placebo didn't improve motor score on the Bayley Scales of Infant and Toddler Development III (adjusted mean difference [aMD] −1.07 points, 95% CI −4.69 to 2.55) or cognitive scores (aMD −1.14, 95% CI −4.26 to 1.99) or language scores (aMD 0.75, 95% CI −2.31 to 3.82) at 12 months of age, reported Anna Chmielewska, MD, PhD, of Umeå University in Sweden, and colleagues.

Nor were there advantages at age 12 months in terms of reduced risk for iron deficiency (RR 0.46, 95% CI 0.16-1.30) or iron deficiency anemia (RR 0.78, 95% CI 0.05-12.46), the group noted in .

At 24 and 36 months, developmental scores were similar between groups as well.

"Exclusive breastfeeding is recommended for approximately 6 months after birth," Chmielewska and colleagues wrote. "However, since the iron content in breast milk is low and iron intakes from complementary foods often are insufficient, prolonged breastfeeding is known to be associated with iron deficiency."

"Associations between iron deficiency anemia and impaired cognition, motor function, and behavior development have been well established, and the negative effects may be irreversible," they added.

But whether iron supplementation actually makes a difference has lacked high-quality evidence, leading to mixed recommendations on supplemental recommendations for breastfed infants after age 4 months. The American Academy of Pediatrics recommends 1 mg/kg/d of iron for all infants who are predominantly or exclusively breastfed from age 4 months until their diet can supply sufficient iron. European guidelines do not recommend routine iron supplementation for exclusively breastfed, normal-birth-weight infants.

"For general practitioners and pediatricians," Chmielewska told MedPage Today, this study provides "more confidence in refraining from iron supplementation in otherwise healthy breastfed infants."

As to why supplementation didn't even impact iron levels, she added in an email: "In this low-risk population, the infants most probably regulated the iron intake between end of intervention (9 months) and time of blood sampling (12 months) so that no difference was seen at this time point."

Infants included in the study were healthy singleton infants born at term for whom breastfeeding accounted for more than 50% of daily feedings and who did not have anemia at 4 months of age.

The trial randomized 220 infants 1:1 to receive iron (1 mg/kg micronized microencapsulated ferric pyrophosphate mixed with water or breast milk) or placebo (maltodextrin) once daily from ages 4 to 9 months.

The study was conducted between December 2015 and May 2020 with follow-up through May 2023 in outpatient settings in Poland and Sweden. In total, 64.7% of the infants completed all three Bayley assessments.

Limitations of the study included that, of the approached families, only 15% agreed to participate, "which may raise concern regarding the generalizability of the results," Chmielewska and colleagues noted. They also acknowledged that developmental assessment was performed using two different versions of Bayley assessments in two countries (Poland and Sweden).

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