According to the study, a prenatal ‘unhealthy diet’ was strongly linked with insulin-like growth factor 2 gene (IGF2) methylation at birth for children with an early-onset persistent (EOP) and consistent behavioural problems (CP).
For the EOP group, a higher IGF2 methylation predicted ADHD symptoms. A prenatal ‘unhealthy diet’ was also linked with higher ADHD symptoms indirectly via higher IGF2 methylation.
IGF2 methylation is a process closely related to the metabolic regulation of glucose homeostasis, cardiovascular functions, and lipid metabolism.
It is thought that excessive IGF2 methylation (via an inadequate nutritional environment) may lead to mental and physical development problems in later life.
The influence of a prenatal diet on the developing foetus has been the focus of a number of studies that demonstrate how a new-born’s health can be determined at such a young age.
The study gathered 164 subjects, 83 of which showed EOP. These were combined with low CP sample (81) drawn from the Avon Longitudinal Study of Parents and Children.
The team, from Leiden University in The Netherlands, and King’s college in London, then took blood samples to measure genomic DNA at birth and when the children were aged seven.
A Food Frequency Questionnaire (FFQ) was used to assess maternal dietary patterns at 32 weeks of gestation, and details of the child’s diet at three, four-and a half, and seven years of age.
In addition, attention deficit hyperactivity disorder (ADHD) symptoms were repeatedly assessed at ages seven, 10, and 13.
“EOP children showed higher levels of ADHD symptoms compared to low CP children. However, means and variances for ADHD differed from zero for the two groups (EOP and low CP youth.)”
“We found that in EOP but not in low CP youth (a) IGF2 DNA methylation at birth was positively correlated with ADHD symptoms and (b) IGF2 DNA methylation at age 7 was negatively correlated with postnatal cumulative risk."
“For the EOP youth, ‘unhealthy diet’ correlated at a trend level with IGF2 DNA methylation at birth and ADHD.”
Previous research has shown diet to be a major influence in methylation of the IGF2. Animal and human studies detail IGF2’s association with developmental abnormalities in the brain associated with ADHD.
Deficiencies in IGF2 have also been linked with psychiatric disorders such as depression and schizophrenia.
Whilst the results generated excitement among the scientific community, the view from some was to wait until further research findings could be ascertained.
The research suffered from a fairly small subset of children, and its findings may not apply to the broader ADHD population.
“Rijlaarsdam et al. show that persistent conduct problems up to 13 years later in children whose mothers ate too much fat and sugar in pregnancy may partly result from excessive methylation, hence silencing, of IGF2, but only if this silencing causes them ADHD,” said Professor John Stein, Emeritus professor of physiology at the University of Oxford.
“IGF2 is an important growth factor in early development of the brain. These associations are somewhat tenuous and certainly do not prove that sugar and fat can cause conduct problems, but all the more interesting because this site on chromosome 11 has already been linked with ADHD and dyslexia.”
Source: Journal of Child Psychology and Psychiatry
Published online ahead of print, DOI: 10.1111/jcpp.12589
“Prenatal unhealthy diet, insulin-like growth factor 2 gene (IGF2) methylation, and attention deficit hyperactivity disorder symptoms in youth with early-onset conduct problems.”
Authors: Jolien Rijlaarsdam et al.