Researchers compared two groups of pregnant women in Australia—one before and one after the country started adding folic acid to bread and other foods. They found that women after the fortification had three times more gestational diabetes (a type of diabetes during pregnancy) than before. The study suggests that while folic acid is important for pregnancy, getting too much of it might actually increase diabetes risk. Scientists think this happens because excess folic acid changes hormone levels in the placenta, which affects how the body handles blood sugar. This finding is important because many countries add folic acid to foods, and doctors may need to rethink how much is safe.

The Quick Take

  • What they studied: Whether adding folic acid to foods (food fortification) might be connected to higher rates of gestational diabetes in pregnant women, and how it affects pregnancy hormones.
  • Who participated: Two groups of pregnant Australian women: 1,164 women before folic acid was added to foods (2010) and 1,300 women after fortification started (2022). Both groups were tracked from early pregnancy onward.
  • Key finding: Gestational diabetes increased from 5% to 15.2% after food fortification began. Women with high folate levels had 48% more cases of gestational diabetes. Folate levels in the blood increased by 259% after fortification started.
  • What it means for you: If you’re pregnant or planning to become pregnant, this suggests you should talk to your doctor about folic acid supplementation rather than taking extra on your own. The research suggests that more folic acid isn’t always better, though folic acid itself remains important for preventing birth defects. This is especially relevant if you live in a country with mandatory food fortification.

The Research Details

Researchers compared two separate groups of pregnant women from Australia at different time periods. The first group (SCOPE study) included 1,164 women studied before 2010, when Australia didn’t add folic acid to foods. The second group (STOP study) included 1,300 women studied after 2010, when mandatory folic acid fortification began. Both groups had their blood tested early in pregnancy to measure folate levels and pregnancy hormones. The researchers then tracked which women developed gestational diabetes during pregnancy and looked for connections between folate levels and diabetes risk.

This type of study is powerful because it compares real-world situations before and after a major change (food fortification). The researchers measured three different pregnancy hormones—prolactin, human placental lactogen, and placental growth hormone—because animal studies suggested these hormones might be affected by high folate intake and could influence blood sugar control.

The study used statistical methods to determine whether the increase in folate levels actually caused the increase in gestational diabetes, or if it was just a coincidence. This helps separate cause from correlation.

This research matters because gestational diabetes affects both mother and baby’s health, and the rates have tripled in Australia in just 12 years. Understanding what’s causing this increase is crucial for public health. By comparing women before and after fortification, researchers could see the real-world impact of this policy change. The study also looked at the biological mechanisms (how excess folate might cause the problem) rather than just noting that the problem exists.

This study has several strengths: it used two large, well-documented groups of pregnant women; it measured actual blood levels rather than relying on memory; and it tracked outcomes over time. However, the study cannot prove that folic acid fortification directly caused the increase in gestational diabetes—other factors in society may have changed too (diet, obesity rates, age of mothers, etc.). The researchers acknowledge this limitation. The study is observational rather than experimental, meaning they observed what happened naturally rather than randomly assigning women to different folate levels.

What the Results Show

After mandatory folic acid fortification began in Australia, gestational diabetes rates nearly tripled, jumping from 5% to 15.2%. At the same time, women’s blood folate levels increased dramatically—serum folate went up 18% and red cell folate (a measure stored in red blood cells) increased by 259%. This means most women after fortification had folate levels above what doctors consider the normal, healthy range.

Women who had folate levels above the normal range had 48% more cases of gestational diabetes compared to women with normal folate levels. This suggests that having too much folate, not too little, might be the problem. The researchers also found that pregnancy hormones changed after fortification—human placental lactogen increased 29% and placental growth hormone increased 13%. These hormones help regulate blood sugar during pregnancy.

Women with excess folate had even higher levels of these hormones (prolactin was 24.2% higher and human placental lactogen was 12.7% higher). The researchers used statistical analysis to suggest that the excess folate likely caused changes in these hormones, which then led to problems with blood sugar control and gestational diabetes.

The study found that 57.6% of women after fortification had folate levels above the clinical reference range—meaning more than half of pregnant women had more folate than doctors consider optimal. This widespread excess folate is a new phenomenon that didn’t exist before fortification. The research also showed that all three pregnancy hormones measured were elevated after fortification, suggesting that excess folate affects multiple hormone systems in pregnancy.

Previous animal studies had suggested that high folic acid intake could impair glucose (blood sugar) regulation during pregnancy, but this is one of the first human studies to show this connection in real pregnancies. The findings align with concerns raised in other research about whether mandatory food fortification might be too much for some populations. This study adds to growing evidence that ‘more is not always better’ when it comes to folic acid supplementation.

The study cannot prove that folic acid fortification directly caused the increase in gestational diabetes because other factors changed in Australia during this time period (such as maternal age, obesity rates, diet patterns, and screening practices). The two groups of women were studied at different times, so differences might be due to other societal changes rather than just folate. The study is observational, not experimental, so it shows association rather than definitive cause-and-effect. Additionally, the study was conducted in Australia, so results may not apply equally to other countries with different fortification levels or different populations.

The Bottom Line

If you are pregnant or planning pregnancy: (1) Talk to your doctor before taking folic acid supplements—don’t assume more is better. (2) Eat folate-rich foods like leafy greens, legumes, and asparagus, which provide folate naturally. (3) Be aware that many fortified foods (bread, cereals, pasta) already contain added folic acid. (4) If you live in a country with mandatory food fortification, discuss with your doctor whether you need additional supplementation. Confidence level: Moderate—this is strong evidence but not yet definitive proof.

This research is most relevant to pregnant women or those planning pregnancy, especially in countries with mandatory folic acid fortification (including Australia, Canada, USA, and others). Women with family history of diabetes should be particularly attentive. Healthcare providers should consider these findings when recommending folic acid supplementation. This is less relevant to non-pregnant individuals, as the study specifically examined pregnancy.

Gestational diabetes typically develops in the second or third trimester of pregnancy. If you reduce folic acid intake or avoid excess supplementation, you wouldn’t expect to see benefits until your next pregnancy, as the study measured folate levels early in pregnancy. Changes in blood sugar control would develop over weeks to months during pregnancy.

Want to Apply This Research?

  • Track daily folic acid intake from all sources (supplements, fortified foods, and natural sources) in micrograms. Log foods like bread, cereals, pasta, and leafy greens. Set a target range of 400-600 micrograms daily (as recommended by most guidelines) rather than exceeding this amount.
  • If pregnant or planning pregnancy: (1) Check supplement labels and avoid taking folic acid supplements if you eat fortified foods regularly. (2) Switch from fortified cereals to non-fortified options if you’re also taking supplements. (3) Focus on natural folate sources (spinach, broccoli, lentils, chickpeas) rather than relying on fortified foods plus supplements. (4) Schedule a conversation with your healthcare provider about your specific folic acid needs before conception.
  • If pregnant: Work with your healthcare provider to monitor blood glucose levels and folate status through routine prenatal blood tests. Track any symptoms of gestational diabetes (increased thirst, frequent urination, fatigue). Keep a food diary to monitor total folate intake from all sources. Discuss results with your doctor at each prenatal visit.

This research suggests an association between excess folic acid and gestational diabetes risk, but does not prove direct causation. Folic acid remains essential for preventing serious birth defects and should not be avoided during pregnancy. Do not change your folic acid intake or supplementation without consulting your healthcare provider. This information is for educational purposes and should not replace personalized medical advice. If you are pregnant or planning pregnancy, discuss these findings with your doctor to determine the appropriate folic acid intake for your individual situation. Women with gestational diabetes should work with their healthcare team on blood sugar management, as this is a serious condition requiring medical supervision.