Adequate folate consumption is recommended for women in preconception and pregnancy to ensure cell growth and development.
But new research from the University of Adelaide and Flinders University, has revealed the need to establish a safe upper limit of consumption.
Current guidelines recommend supplementation with 400 to 500 micrograms (µg) of folic acid daily, starting at least one month prior to conception and continuing through the first trimester, to reduce the risk of neural tube defects such as spina bifida.
Dr Tanja Jankovic-Karasoulos, from the University's School of Biomedicine and Robinson Research Institute, has found excess maternal folate levels - caused by the dual impact of folic acid (FA) food fortification and higher-than-recommended supplementation doses during pregnancy - can be linked to a rise in gestational diabetes Mellitus (GDM).
The folate levels of more than 2000 women pre-fortification and post fortification were analysed at Flinders University as part of the study, which was published in the journal Nutrients.
"Our study shows that excess maternal folate significantly increases GDM risk in our post-fortification pregnancy cohort," says Dr Jankovic-Karasoulos.
"We suspect that increased FA intake over the past 10 to 15 years is contributing to the steady rise in GDM prevalence in Australia."
The incidence of gestational diabetes in Australia has more than tripled from 5.6 per cent of women in 2010 to 19.3 per cent in 2022.
"The placenta is central to regulating maternal glucose tolerance in pregnancy, so we need to understand how high FA intake affects placental function and, in turn, insulin resistance and gestational diabetes risk," says Dr Jankovic-Karasoulos.
Flinders University NHMRC Investigator Fellow Professor Claire Roberts said understanding the potential harms of excess FA intake is of major public health importance.
"The use of FA is recommended worldwide, but we need to keep investigating unexpected implications, plus how to identify women early in pregnancy at risk of gestational diabetes to protect the baby from adverse effects of high maternal blood glucose for the best start in life," says Professor Roberts.
Researchers emphasise the importance of adequate folate in pregnancy but highlight the need to establish a safe upper limit of FA intake and to improve guidelines on FA supplementation during pregnancy which would protect the fetus right at the beginning of gestation against neural tube defects but also protect the mother and fetus from adverse effects of high blood glucose.
