Folic acid has long been a cornerstone of prenatal care, credited with preventing serious birth defects such as spina bifida. But new research from South Australia suggests that taking more than recommended may carry unintended risks.
A study published in Nutrients found that excessive folic acid intake during pregnancy was linked to a higher chance of developing gestational diabetes. Researchers point to the combined effects of food fortification and high-dose supplementation as possible drivers.
“Our study shows that excess maternal folate significantly increases GDM risk in our post-fortification pregnancy cohort,” said Dr. Tanja Jankovic-Karasoulos of the Robinson Research Institute at the 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.”
Gestational diabetes has become increasingly common in Australia, with cases more than tripling from 5.6% in 2010 to 19.3% in 2022. The condition raises risks for both mother and baby, including complications during birth and a higher likelihood of developing type 2 diabetes later in life.
The researchers stress that folic acid remains essential for early pregnancy, but that intake beyond the recommended 400-500 micrograms daily may be problematic.
“Our study suggests that higher-than-recommended FA intake may have unintended consequences for pregnancy,” Jankovic-Karasoulos noted.
Professor Claire Roberts of Flinders University added that understanding the balance is critical.
“The use of FA is widely recommended worldwide, but we need to keep investigating unexpected implications, plus how to identify women at risk of gestational diabetes early in pregnancy to protect the baby from adverse effects of high maternal blood glucose for the best start in life.”
The United States also requires folic acid fortification in grains, a policy in place since 1998. Most prenatal vitamins add another 400-800 micrograms of folic acid, which means American women may also be at risk of excess intake when combining supplements with fortified foods.
In the U.S., about 7-10% of pregnancies are affected by gestational diabetes. While no large U.S. studies have yet confirmed the same link, experts agree on one point: more isn’t always better. Women planning for pregnancy should follow established guidelines, not exceed them and talk with their doctor about supplementation needs.
The goal, researchers say, is not to reduce folic acid intake below safe levels, as it remains vital for preventing neural tube defects, but to establish a clearer upper limit that protects both mother and child.
The study was funded by the National Health and Medical Research Council Investigator grant program and Flinders Foundation Health Seed grants.