It has been suggested that modifying formula milk promotes cognitive development, but trial evidence that modified formulas result in long term cognitive advantages is inconclusive.
To address this, researchers from UCL Great Ormond Street Institute of Child Health and Institute of Education, in the UK, set out to compare differences in academic performance between adolescents who were randomly given modified or standard infant formula as babies.
They analysed results from seven randomised trials of nutritionally modified infant formula carried out at five English hospitals between August 1993 and October 2001 involving 1,763 adolescents.
Two of the trials tested formula milks enriched with a long chain polyunsaturated fatty acid (LCPUFA), one of the many breast milk constituents with a role in brain development; one tested added iron; two tested formula milks with higher macronutrient concentrations; and two tested formulations with added sn-2 palmitate or nucleotides, not thought to relate to cognition.
In 2018, these trial data were linked to school records, focusing on what effect (if any) the formula had had on scores for national mandatory exams (GCSEs) in maths and English at ages 11 and 16 years, as well as eligibility for special educational needs support and achieving five or more GCSE grades of C or higher.
Results were gathered for 1,607 (91.2%) participants linked to school records.
No benefit was found for performance in maths exams at age 16 years for children given any modified formula.
There was no difference in scores for English at age 16, or for maths and English at age 11, between children who had standard formula as infants and those who had nutrient enriched, added iron, sn-2 palmitate or nucleotide formulas.
However, at age 11, children who had been given the LCPUFA supplemented formula scored lower in both English and maths.
The researchers point out that the trials were carried out several decades ago and, since then, the composition of formulas and neonatal care have changed.
Nevertheless, the study’s strengths include the high rate of follow-up and the use of GCSE scores that the authors say have real world relevance to young people and their future.
“In summary, differences in academic performance between modified and standard formulas were consistent with differences measured in the original trials and in the external literature; that is, no benefit of the infant formula modifications on cognitive outcomes,” they write.
“This study sets a precedent for other trials and cohorts to use linkage to administrative data to answer important questions about long term outcomes in children and young people,” they add.
Action needed on misleading claims
In a linked editorial, researchers at the University of Glasgow argue that added nutrients could also do harm and that baby milk trials were often not well conducted.
They conclude: “Recently published evidence suggests a need to better regulate research into infant formulas and to ensure that this evidence is used to remove unnecessary and potentially harmful nutrients from formula milk, and to prevent misleading promotional claims.”
The editorial notes that this new study found no differences in cognition associated with iron supplementation, but they note that a previous study found reduced cognition at age 16 years among children who had received formula milk supplemented with iron.
The researchers at the University of Glasgow note that breast milk contains little iron, and the likely evolutionary reason for this is that iron in the gut facilitates the growth of pathogenic bacteria. Yet manufacturers of formula milk advertise the addition of iron to follow-on milks, which could be interpreted as an advantage of formula milk over breast milk.
The editorial states: "Given the lack of benefit associated with supplementary iron and its possible adverse effect on growth and now cognition, it is time to consider whether current regulations governing the composition of formula milks need review worldwide."
Source: BMJ
Verfürden. M.L., Gilbert. R., Lucas. A., Jerrim. J., and Fewtrell. M.,
"Effect of nutritionally modified infant formula on academic performance: linkage of seven dormant randomised controlled trials to national education data"
doi: 10.1136/bmj-2021-065805