New evidence links high folate intake to gestational diabetes
Australian researchers warn that high doses of folic acid in pregnancy, coupled with fortified foods, may be contributing to a sharp rise in gestational diabetes mellitus (GDM). The study, conducted with more than 2,000 pregnant women, suggests that excessive folate exposure could be a contributing factor behind the tripling of GDM rates in the past decade.
What the study found
The researchers compared a pre-fortification cohort (pregnant before 2009) with a post-fortification cohort (pregnant after 2009). They reported a marked increase in GDM: 5% in the pre-fortification group versus 15% in the post-fortification group. They also observed higher levels of folate-related biomarkers, including serum folate and red cell folate, in the post-fortification group, alongside elevated placental hormones that influence insulin sensitivity.
Notably, the proportion of women with red cell folate above the normal range rose from 0.5% to 57.6% after fortification. Those with excess red cell folate had a 48% higher incidence of GDM, according to the data summarized in Nutrients by Flinders University and the University of Adelaide researchers.
Interpreting the results
Lead author Dr. Tanja Jankovic-Karasoulos emphasizes that while folic acid remains essential for preventing neural tube defects, excess exposure in a fortified environment may carry risks. “The challenge is to maintain protection against neural tube defects while avoiding excess exposure,” she said. The team advocates revisiting supplementation guidelines to prevent unnecessary overconsumption, particularly beyond the first trimester.
Dr. Jankovic-Karasoulos notes that many women may obtain sufficient folate from fortified foods, and some will not need extra supplements after the early pregnancy window. She urges healthcare providers to reinforce the principle of the “right dose, right window” and to avoid duplicating folic acid through multivitamins unless clinically indicated.
Implications for guidelines and practice
The study calls for a balanced approach to folate recommendations in Australia, where mandatory food fortification and common supplement use have created a milieu of high folate exposure. The authors suggest considering folate status checks for women with high or unclear exposure and maintaining vigilant GDM screening and lifestyle counseling for those with high folic acid intake.
They acknowledge that higher folate levels might be necessary for certain populations, such as women with prior neural tube defects or specific medical conditions, where doses may range from 800 micrograms to 5 milligrams. However, the default recommendation should align with the standard 400–500 micrograms before conception and during the first trimester unless otherwise indicated.
Context and caution
While the association between high folate exposure and GDM is compelling, the authors caution that causality is not definitively established. Other known risk factors for GDM—age, obesity, and ethnicity—also factor into the overall risk, but they do not fully explain the observed rise. Animal studies and physiological reasoning about placental hormones and insulin resistance support the plausibility of folate’s role, but further research is needed to confirm causation and guide policy changes.
What this means for pregnant people
For now, expectant parents should discuss folate needs with their healthcare providers. The consensus remains that folic acid is vital in the periconception period, but excess intake beyond the first trimester may not be beneficial for everyone. Avoid doubling up on supplements that already contain folic acid, and adhere to guideline-based dosing unless there is a clear medical reason to adjust.
Bottom line
As Australia navigates a fortified food landscape, experts urge a careful balance: continue to shield against neural tube defects while preventing unnecessary folate excess that could contribute to gestational diabetes. Future guidelines may evolve to reflect these nuanced findings.
