Researchers in the UK tested blood samples from nearly 47,000 people to understand how common folate deficiency is and whether adding more folate to food could cause problems with vitamin B12. They found that about 73% of women of childbearing age don’t have enough folate in their blood to protect babies from birth defects, and young women aged 21-25 are at even higher risk (85.5%). The good news: the study found no evidence that having high folate levels harms vitamin B12 status, which was a concern some people had about adding folate to food. This research supports the idea that the UK should start adding folic acid to flour and other foods, similar to what many other countries already do.

The Quick Take

  • What they studied: How many people in the UK don’t have enough folate (a B vitamin) in their blood, and whether adding more folate to food could hurt vitamin B12 levels
  • Who participated: 47,240 people who had blood tests at a UK laboratory between August 2023 and January 2025. The study focused especially on women of childbearing age (16-50 years old)
  • Key finding: Nearly 3 out of 4 women aged 16-50 don’t have enough folate to protect babies from neural tube defects (birth defects of the brain and spine). Even more concerning, 85.5% of young women aged 21-25 have low folate. However, people with high folate levels showed no problems with their vitamin B12 status
  • What it means for you: If you’re a woman planning to have children, you may not be getting enough folate from your current diet. The research suggests that adding folic acid to common foods (like flour) would be safe and wouldn’t interfere with vitamin B12 absorption, which was a previous concern. This is especially important for young women who are most at risk

The Research Details

This study looked at blood test results from nearly 47,000 people tested at a UK laboratory over about 18 months (August 2023 to January 2025). The researchers measured two things in the blood: folate levels and a special form of vitamin B12 called holoTC (the ‘active’ form that your body can actually use). They compared these measurements to see if people with high folate had any problems with their B12 levels.

For the main analysis about folate and B12 interaction, they focused on 39,374 people who had measurements for both nutrients. They also paid special attention to women of childbearing age, since folate is especially important for preventing birth defects early in pregnancy. The study used a machine called an immunochemical analyser to measure the blood levels accurately.

This approach is important because it gives us real-world information about what’s actually happening in the UK population right now. Rather than studying a small group in a lab, researchers looked at thousands of actual blood test results. This helps answer the practical question: ‘Do we really have a folate problem in the UK, and is it safe to add folate to food?’ The large sample size makes the findings more reliable and representative of the general population.

This study has several strengths: it’s based on a very large number of real blood samples (nearly 47,000), it used standardized laboratory equipment to measure nutrients, and the data came from actual medical testing rather than people’s memories of what they ate. However, the study only shows what’s happening at one point in time—it doesn’t follow people over months or years to see how their folate levels change. Also, we don’t know much about the people tested (age, diet, health conditions) beyond what’s in their blood results, which limits what we can conclude about why some people have low folate.

What the Results Show

The research found a significant folate deficiency problem in the UK, especially among women of childbearing age. For women aged 16-50, about 72.7% had folate levels below 24.3 nM/L—which is the level needed to protect babies from neural tube defects (serious birth defects affecting the brain and spine). The situation is even more concerning for young women aged 21-25, where 85.5% had insufficient folate levels.

The second major finding addresses a common concern about adding folate to food. Some people worried that if we added too much folate, it might interfere with vitamin B12 and cause B12 deficiency. The researchers tested this by looking at people with the highest folate levels (the top 10% of the study). These people had an average folate level of 43.9 nM/L and also had high vitamin B12 levels (119.2 pM/L). Importantly, they found no increased risk of vitamin B12 deficiency in these high-folate individuals.

This is reassuring because it suggests that adding folic acid to food (fortification) would not create a new problem with B12 deficiency. The study found no evidence of a negative relationship between high folate and B12 status across the entire population studied.

While the study’s main focus was on folate deficiency and its relationship to B12, the findings also highlight that young adult women (ages 21-25) are at particularly high risk of low folate. This age group is important because many women in this range may become pregnant, and folate is critical in the earliest weeks of pregnancy—often before a woman even knows she’s pregnant. The research suggests that relying on individual supplementation or dietary choices hasn’t solved the folate deficiency problem in the UK, which supports the argument for population-wide food fortification.

This research adds to growing evidence that folate deficiency is a significant public health issue in the UK. Many other countries, including the United States, Canada, and Australia, have already implemented mandatory folic acid fortification of flour and grain products, and they’ve seen dramatic reductions in neural tube defects. This UK study provides current data showing that without similar fortification, the UK continues to have high rates of folate deficiency. The finding that high folate doesn’t harm B12 status contradicts some earlier concerns and aligns with research from countries that have already implemented fortification without seeing B12 problems.

This study has some important limitations to understand. First, it’s a snapshot in time—it shows what’s happening now but doesn’t tell us how folate levels change over time or what causes them to be low. Second, the researchers only had blood test results; they didn’t have detailed information about what people ate, their health conditions, medications, or other factors that might affect folate levels. This means we can describe the problem but can’t fully explain why it exists. Third, the study looked at people who had blood tests done, which might not represent the entire UK population—people getting blood tests might have different health profiles than the general public. Finally, while the study shows that high folate doesn’t harm B12 in this population, it doesn’t prove that fortification would be safe and effective in practice, since fortification would affect the entire population differently.

The Bottom Line

Based on this research, health experts should seriously consider implementing mandatory folic acid fortification in the UK (adding folic acid to flour and other staple foods). The evidence suggests this would be safe—it won’t cause B12 problems—and it would address a significant public health issue. For women planning to become pregnant or who could become pregnant, taking a folic acid supplement (400 micrograms daily) is recommended, since many women don’t get enough folate from food alone. This recommendation has high confidence because it’s based on a very large sample and aligns with practices in other countries that have seen good results.

This research is most important for women aged 16-50, especially those planning to have children or who could become pregnant. It’s also relevant for healthcare policymakers and government officials deciding on food fortification policies. Men and older women should care because folate is important for overall health, not just pregnancy, though the immediate public health concern is protecting babies from birth defects. If you have vitamin B12 deficiency or are being treated for it, this research is reassuring—it suggests that increasing folate intake won’t make your B12 problem worse.

If the UK implemented folic acid fortification, the benefits would likely appear within months to a year, as folate levels in the population gradually increased. For individual women taking folic acid supplements, blood folate levels typically improve within weeks. However, the most important benefit—preventing neural tube defects—would only be seen in future pregnancies, which could take months to years depending on individual circumstances. It’s important to note that folic acid works best when taken before pregnancy begins, so women shouldn’t wait until they’re pregnant to ensure adequate folate levels.

Want to Apply This Research?

  • Track daily folic acid intake (in micrograms) from supplements and fortified foods. Set a goal of 400 micrograms daily if you’re a woman of childbearing age, and log each dose of supplements taken. This creates a simple yes/no daily tracker: ‘Did I get my folic acid today?’
  • If you’re a woman aged 16-50, start taking a daily folic acid supplement (400 micrograms) or increase consumption of folate-rich foods like leafy greens, legumes, and fortified cereals. Use the app to set a daily reminder to take your supplement at the same time each day (like with breakfast). Track which foods you eat that contain folate to see if you’re getting enough from diet alone.
  • Create a monthly check-in where you review your folic acid compliance rate (what percentage of days did you take your supplement or eat folate-rich foods?). If you’re planning pregnancy, discuss getting your folate levels tested with your doctor and track the results over time. Set a goal of 90% compliance with daily folic acid intake and monitor how consistently you meet this target.

This research shows that folate deficiency is common in the UK and that adding folic acid to food would be safe. However, this study alone cannot determine whether food fortification should be implemented—that decision involves many factors including cost, regulatory considerations, and public health priorities. If you’re pregnant, planning to become pregnant, or have concerns about your folate or B12 levels, consult with your healthcare provider before starting supplements. This information is for educational purposes and should not replace professional medical advice. Individual nutritional needs vary based on health conditions, medications, and other factors that only a healthcare provider can assess.