From 13 December 2026, folic acid will be added to most non-wholemeal wheat flour produced or imported into the UK (source). The change is expected to prevent around 200 cases of neural tube defects each year, including spina bifida (source).

But the announcement has also prompted concerns about the safety of folic acid, with some social media posts claiming that it is poorly absorbed, harmful to people with certain genetic variants, or associated with unwanted side effects.

Flour fortification is nothing new, and most UK non-wholemeal wheat flour has already been fortified with essential vitamins and minerals for more than 80 years. So why is folic acid being added, what does the scientific evidence tell us about its benefits and risks, and how can we separate legitimate concerns from misinformation?

Why is folic acid being added to flour in the UK?

Folic acid is a manufactured form of vitamin B9, an essential nutrient involved in DNA synthesis, cell division and the formation of healthy red blood cells (source).

Vitamin B9 occurs naturally in foods as folate, particularly in leafy green vegetables, beans, lentils and some fruits. Folic acid is the form commonly used in supplements and fortified foods because it is stable and well absorbed (source).

Getting enough folate is particularly important during early pregnancy, when the developing baby's brain and spinal cord are forming. During the first few weeks after conception, a structure called the neural tube develops and closes. If it doesn't close properly, serious birth defects can occur, including spina bifida, which affects the spinal cord, and anencephaly, which affects the development of the brain and skull (source).

Crucially, the neural tube normally closes within approximately 28 days of conception, often before someone knows they're pregnant (source). Although UK guidance already recommends taking 400 micrograms (µg) of folic acid daily before pregnancy and during the first 12 weeks, not everyone takes supplements early enough (source).

An estimated half of pregnancies in the UK are unplanned, meaning many people may not begin taking supplements before this critical stage of development (source). Adding folic acid to a widely consumed staple food helps increase folate intake across the population, including among people who might otherwise miss this important early window.

This is the main rationale behind mandatory flour fortification: preventing avoidable birth defects without relying entirely on individual supplementation.

Natural sources of folate, bowls of spinach, lentils and white beans on a wooden table with kale, asparagus, whole oranges and a halved orange.
Natural sources of folate: leafy greens, beans, lentils and fruit

Isn't UK flour already fortified with vitamins and minerals?

Yes. Although the addition of folic acid has attracted considerable attention, fortifying flour with essential nutrients is nothing new in the UK.

In fact, the practice dates back to the 1940s, when calcium was added to flour during the Second World War to help protect nutritional health at a time when food supplies were restricted (source).

Today, most non-wholemeal wheat flour produced or imported into the UK is already required to contain four added vitamins and minerals:

  • Calcium: Essential for maintaining healthy bones and teeth. Its addition was originally intended to improve calcium intake when dairy products were scarce.
  • Iron: Needed to produce haemoglobin, which carries oxygen around the body. Inadequate intake can contribute to iron-deficiency anaemia.
  • Thiamin (vitamin B1): Helps the body release energy from food and supports normal nervous system function.
  • Niacin (vitamin B3): Supports energy metabolism and the normal functioning of the nervous system.

Iron, thiamin and niacin are naturally present in wheat, but some are lost when the bran and germ are removed to produce white flour. Fortification helps restore these nutrients, while added calcium increases the flour's nutritional value (source).

Has flour fortification been a success?

Flour fortification has long been an established part of the UK's approach to preventing nutrient deficiencies. Because bread and other flour-containing foods are widely consumed, fortification can provide a practical way to improve nutrient intake without requiring people to change their eating habits or remember to take supplements (source).

However, it is difficult to quantify exactly how many cases of nutrient deficiency have been prevented by the UK's longstanding flour fortification programme. Changes in dietary patterns, food availability and healthcare have occurred alongside fortification.

Its long history therefore demonstrates that adding nutrients to flour is an established practice, rather than proving that every fortification policy is automatically beneficial.

The strongest evidence for the benefits of adding folic acid specifically comes from randomised trials demonstrating the prevention of neural tube defects and population studies showing reductions following fortification in other countries (source, source).

The important point is that folic acid isn't introducing an entirely new concept. It's adding another essential vitamin to an existing public health programme, with the aim of preventing serious birth defects.

The December 2026 regulations will also increase the required minimum levels of iron and niacin, as well as the required range for added calcium carbonate. The thiamin requirement will remain unchanged (source).

How effective is folic acid fortification?

Folic acid fortification is among the best-established nutritional public health interventions. The evidence that folic acid prevents neural tube defects is supported by landmark randomised controlled trials.

In 1991, the Medical Research Council Vitamin Study demonstrated that folic acid supplementation reduced the recurrence of neural tube defects by 72% among women who had previously experienced a neural tube defect-affected pregnancy (source).

A subsequent randomised trial, published in the New England Journal of Medicine in 1992, found that a multivitamin containing folic acid prevented first-occurrence neural tube defects. Because the intervention contained several vitamins, the study could not isolate the independent contribution of folic acid (source). These trials established the preventive benefits of periconceptional supplementation.

Evidence from national fortification programmes provides additional insight into what happens when folic acid is added to commonly consumed foods. The United States introduced mandatory folic acid fortification of enriched cereal-grain products in 1998. Subsequent surveillance estimated a 28% reduction in the prevalence of neural tube defects, including spina bifida and anencephaly, following fortification (source).

Although before-and-after comparisons cannot establish that fortification alone caused the entire reduction, the findings are consistent with the randomised trial evidence.

Fortification has also substantially improved population folate status. An analysis of US national nutrition survey data found that, among women of childbearing age, the prevalence of low serum folate concentrations fell from approximately 21% before fortification to less than 1% afterwards. The prevalence of low red blood cell folate concentrations also fell, from approximately 38% to 5% among those of childbearing age (source).

For the UK, government modelling estimates that mandatory fortification will reduce neural tube defects by approximately 20%, preventing around 200 cases each year (source). These are projected benefits rather than outcomes already observed in the UK. Nevertheless, they are supported by decades of research and experience from other countries.

Which types of flour and bread will contain folic acid?

Under the new regulations, non-wholemeal flour made from common wheat must contain 250 µg of added folic acid per 100 g of flour (source). This includes the white wheat flour commonly used to make bread, rolls, pastries, cakes and biscuits.

However, there are important exceptions. Wholemeal flour is exempt from mandatory folic acid fortification, as are flours not made from common wheat, such as rye, oats and spelt flour. Flour produced by qualifying small mills is also exempt, as are certain specialised products (source).

This means not every loaf of bread or flour-containing food will necessarily contain added folic acid. Imported finished products containing flour are also not automatically covered by the same requirements.

How can you tell whether your bread contains folic acid?

Check the ingredients list. Where folic acid has been added through fortified flour, it should be declared on the label, often alongside other added nutrients such as calcium, iron, niacin and thiamin (source).

Some products manufactured or labelled before the implementation date may also remain on sale under transitional arrangements.

White and wholemeal loaves, bread rolls and bowls of flour and oats on a wooden kitchen table by a sunny open window.
White wheat flour and bread (left) will be fortified with folic acid; wholemeal, rye, oat and spelt flour and bread (right) are exempt

Is folic acid fortification safe?

For most people, the quantities of folic acid added to flour are considered safe. This conclusion is supported by assessments from scientific advisory bodies, including the UK's Scientific Advisory Committee on Nutrition (SACN), which has reviewed the benefits and potential risks of mandatory fortification (source).

However, there are several legitimate questions worth addressing, particularly around side effects mainly associated with high-dose supplements, the potential for folate intake to mask vitamin B12 deficiency, the effects of sustained high intakes, and genetic differences in folate metabolism.

What are the side effects of folic acid?

Folic acid supplements can rarely cause side effects, including nausea, bloating, flatulence and reduced appetite. Allergic reactions are possible but rare (source).

However, it's important to distinguish between taking folic acid as a supplement and consuming the much smaller amounts added to flour.

Under the new policy, 100 g of flour will contain 250 µg of added folic acid. A food containing 40 g of fortified flour would therefore provide approximately 100 µg of added folic acid, before accounting for any losses during preparation (source).

This is considerably less than the 400 µg daily supplement recommended around pregnancy. There is no convincing evidence that consuming folic acid at the levels expected from UK flour fortification causes widespread adverse effects (source).

Can folic acid mask vitamin B12 deficiency?

This is one of the more established concerns surrounding high folic acid intake.

Vitamin B12 deficiency can cause anaemia and neurological damage. High doses of folic acid may correct the anaemia associated with B12 deficiency without correcting the underlying neurological problems. This has raised concerns that folic acid could delay diagnosis and treatment, although evidence of this occurring at intakes up to 1,000 µg per day is lacking (source).

The concern is particularly relevant to older adults, who are more likely to experience problems absorbing vitamin B12. Some observational research has also associated high folate status with poorer neurological outcomes among older adults with low vitamin B12 status. However, these findings do not establish that folic acid itself causes neurological damage (source).

For these reasons, scientific advisory bodies have considered vitamin B12 deficiency when evaluating the safety of folic acid fortification (source, source).

The adult tolerable upper intake level for folic acid is 1,000 µg per day from supplements and fortified foods (source). This is not a threshold at which harm suddenly occurs, but a precautionary limit intended to minimise potential risks.

The UK fortification level was selected partly to reduce the likelihood of people exceeding this amount. Importantly, the possibility of masking B12 deficiency at high intakes does not mean that the relatively small quantities added to flour pose the same risk.

What about unmetabolised folic acid?

Another concern is that folic acid is a manufactured form of vitamin B9 and must be converted through several metabolic steps before it can contribute to normal folate metabolism. However, the fact that folic acid is synthetic does not inherently make it harmful. Assuming that something is safer simply because it is natural is an example of the appeal to nature fallacy. What matters is what the scientific evidence tells us about its benefits and risks.

Unlike naturally occurring folate in food, folic acid is relatively stable and generally well absorbed. This is one reason it is used in supplements and food fortification. However, some folic acid can enter the bloodstream without first being converted into other forms of folate. This is known as unmetabolised folic acid (source).

In a small human intervention study, researchers investigated the appearance of unmetabolised folic acid after participants consumed bread containing different doses of folic acid. Unmetabolised folic acid was detected following the 400 µg/day bread regimen but not following the 100 or 200 µg/day bread regimens under the study conditions (source).

However, the study was small and involved participants who had first taken folic acid supplements for 14 weeks, and should not be interpreted as establishing a universal intake threshold.

More importantly, detecting unmetabolised folic acid in the bloodstream does not automatically mean that it is harmful. At present, there is insufficient evidence to establish that the presence of unmetabolised folic acid itself causes adverse health effects (source).

The distinction is important: a plausible biological concern is not the same as demonstrated harm.

Can folic acid increase cancer risk?

Some research has raised questions about whether high intakes of folic acid might influence the development or progression of certain cancers.

Folate is needed for DNA synthesis and cell division. While adequate folate status supports normal cellular function, researchers have investigated whether very high intakes could potentially promote the growth of some pre-existing abnormal cells.

For example, a randomised trial involving people with a history of colorectal adenomas found no reduction in adenoma recurrence with 1 mg of folic acid daily and raised concerns about advanced lesions (source).

However, larger analyses provide important context. A meta-analysis published in The Lancet, involving almost 50,000 participants from randomised trials, found no statistically significant increase in overall cancer incidence with folic acid supplementation during the trial periods (source).

These findings do not establish that every possible long-term risk has been excluded. Nevertheless, the available evidence does not demonstrate that the lower doses of folic acid provided through flour fortification increase cancer risk (source, source).

Is folic acid harmful for people with an MTHFR gene variant?

A particularly common claim online is that people with an MTHFR gene variant cannot properly metabolise folic acid and should therefore avoid fortified foods.

This is not an accurate interpretation of the evidence. The MTHFR enzyme helps convert folate into a form the body can use in important metabolic processes. Certain common genetic variants, particularly C677T, can reduce the activity of this enzyme (source).

However, reduced enzyme activity does not mean someone is unable to use folic acid. Research shows that people with common MTHFR variants can still absorb and benefit from folic acid, even if their blood folate levels tend to be slightly lower than those without these variants. This is particularly true for people who inherit two copies of the C677T variant, known as the TT genotype (source).

Another randomised trial found that consuming folate-rich foods, including fortified foods, or taking folic acid supplements improved folate status even among people with the TT genotype, although they may require somewhat higher intakes to achieve similar homocysteine concentrations (source).

Some online commentators recommend methylfolate supplements instead of folic acid for everyone with an MTHFR variant. However, folic acid remains the form with the most extensive direct evidence for preventing neural tube defects (source, source).

The US Centers for Disease Control and Prevention (CDC) confirms that common MTHFR variants are not a reason to avoid folic acid or foods fortified with it (source).

Are there benefits beyond pregnancy?

Although preventing neural tube defects is the primary reason for introducing fortification, folate is important throughout life.

It contributes to DNA synthesis, normal cell division and red blood cell formation. Inadequate folate intake can lead to megaloblastic anaemia, a condition in which the body produces abnormally large, poorly functioning red blood cells. This is why folate deficiency can cause symptoms such as fatigue, weakness and shortness of breath (source).

Increasing folic acid intake through fortified foods can improve folate status and reduce the prevalence of deficiency across the population. This has been demonstrated in countries with established fortification programmes (source).

However, it is important not to overstate the benefits. Having adequate folate is essential for health, but consuming additional folic acid beyond what the body needs does not necessarily provide further benefits. For most people, a balanced diet containing folate-rich foods remains an important foundation for good nutrition.

Do pregnant women still need folic acid supplements?

Yes. The introduction of mandatory flour fortification does not replace existing advice on folic acid supplementation. The NHS recommends that people who are pregnant or trying to conceive take 400 µg of folic acid daily, ideally starting three months before pregnancy and continuing through the first 12 weeks (source).

Some people at increased risk of a neural tube defect-affected pregnancy may require a higher prescribed dose, commonly 5 mg daily, under medical supervision (source).

Fortification is designed to provide additional protection across the population, particularly where pregnancies are unplanned or supplements are not taken early enough. It should be seen as a complement to supplementation, not a substitute.

A slice of buttered wholemeal toast on a white plate beside a glass of water and yellow tablets next to an amber bottle.
The NHS recommends that people who are pregnant or trying to conceive take 400 µg of folic acid daily

The bottom line

Adding folic acid to UK flour is a carefully considered public health measure backed by substantial scientific evidence.

It's also worth remembering that flour fortification is not new. The UK has been adding essential vitamins and minerals to flour for more than 80 years, and folic acid is an extension of this established approach.

Randomised trials have demonstrated that periconceptional folic acid-containing interventions can prevent neural tube defects, while experience from countries with established fortification programmes shows improvements in folate status and meaningful reductions in these serious birth defects (source, source, source).

In the UK, the policy is expected to prevent around 200 cases of neural tube defect affected pregnancies each year (source).

Concerns about high folic acid intake, vitamin B12 deficiency and possible long-term effects deserve scientific scrutiny. However, the evidence does not support claims that the amounts added to flour are broadly harmful, or that people with common MTHFR variants cannot safely consume folic acid (source, source).

When encountering alarming claims about folic acid online, it's worth considering whether the source has a financial or promotional interest such as selling an alternative product, or is seeking views and followers. Rather than relying on dramatic headlines or isolated studies, the most reliable approach is to consider the full body of scientific evidence and the conclusions of independent scientific experts.

The policy is not without limitations, and continued monitoring will be important. But when the likely benefits and potential risks are considered together, mandatory folic acid fortification represents a well-supported opportunity to prevent serious, avoidable birth defects.