Excessive folic acid intake in pregnancy linked to gestational diabetes

The rise in gestational diabetes mellitus (GDM) could, in part, be caused by excess maternal folate levels, according to a new study. These high doses of folate are due to the dual impact of folic acid in food fortification and higher-than-recommended supplementation doses during pregnancy.

The incidence of GDM in Australia has more than tripled, rising from 5.6% in 2010 to 19.3% in 2022. The team behind the study say it highlights the urgent need to establish a safe upper limit for folic acid intake during pregnancy and to improve guidelines on folic acid supplementation during pregnancy. The research, by Flinders University and Adelaide University researchers, is based on data from more than 2,000 women and 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, from the Robinson Research Institute at University of Adelaide. ‘We suspect that increased FA intake over the past 10-15 years is contributing to the steady rise in GDM prevalence in Australia.’

Adequate folate is essential for DNA formation and proper cell growth and development. Current guidelines recommend supplementation with 400–500 µg 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.

‘Our study suggests that higher-than-recommended FA intake may have unintended consequences for pregnancy,’ says Dr Jankovic-Karasoulos. ‘The placenta is central to regulating maternal glucose tolerance in pregnancy, so we need to understand how high folic acid intake affects placental function and, in turn, insulin resistance and gestational diabetes risk.’