A new Australian study published in Nutrients has raised concerns over the country’s mandatory folic acid food fortification program, suggesting it may be linked to the sharp rise in gestational diabetes mellitus (GDM) seen in recent years.
Researchers examined data from two major cohorts of pregnant women recruited before and after Australia’s 2009 folic acid fortification mandate. The analysis included 2,464 participants from the Screening for Pregnancy Endpoints (SCOPE) cohort and the Screening Tests to Identify Poor Outcomes of Pregnancy (STOP) cohort.
The study found that following fortification, GDM rates tripled from 5% to 15.2%, while maternal folate stores increased by 259%. More than half of women in the post-fortification group recorded red cell folate levels above the recommended clinical range, compared with just 0.5% prior to the policy change.
Researchers also identified significant hormonal changes that may influence glucose metabolism. Levels of human placental lactogen (hPL) rose by 29% and placental growth hormone (GH2) by 13%. While hPL appeared to play a protective role, GH2 was linked to a higher risk of diabetes.
Notably, excess red cell folate—rather than serum folate—was associated with greater risk. Women with elevated stores showed a 48% higher incidence of GDM, and every 500 nmol/L increase corresponded to a 34% rise in risk. High triglyceride levels also emerged as an independent predictor.
Australia has experienced a steep rise in GDM, with rates climbing from 5.6% in 2010 to 19.3% in 2022. While maternal age and obesity contribute to the trend, researchers argue they cannot fully explain the surge, pointing to folic acid overexposure as a possible environmental driver.
The findings highlight a paradox: while fortification successfully reduced folate deficiency and protected against neural tube defects, it may have inadvertently created a new public health challenge.
The authors emphasize that folic acid remains vital in early pregnancy but call for a reassessment of current fortification and supplementation policies. They recommend setting upper intake limits to balance the prevention of birth defects with safeguarding maternal metabolic health.
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