Vitamin B9 (Folate / Folic acid)

Folate is the natural form of vitamin B9, present in food. Folic acid is the synthetic form used in supplements and food fortification; the body converts it to active folate. Both are needed for the same purpose: making new DNA, building new cells, and supporting the nervous system. The body needs folate every day; demand jumps in early pregnancy when an embryo is growing rapidly.

The link with pregnancy is the most consequential public-health story in this entry. The neural tube, the early structure that becomes the brain and spinal cord, closes in the first four to six weeks after conception, often before a woman knows she is pregnant. Adequate folate at that point reduces the risk of neural tube defects, including spina bifida and anencephaly. The NHS recommendation is to take folic acid before pregnancy and through to 12 weeks, exactly because the protective window is so early. The Department of Health and Social Care concluded in 2021 that non-wholemeal wheat flour in the UK would be fortified with folic acid; the fortification is being introduced to add a baseline of folic acid to the staple diet so that unplanned pregnancies are also better protected. The fortification does not replace the supplement recommendation for women planning a pregnancy.

Folate beyond pregnancy: folate works closely with vitamin B12 to make red blood cells. A folate-rich diet supports normal cell turnover throughout life. Folate deficiency in adults causes a specific type of anaemia (megaloblastic anaemia, large red blood cells that work poorly), with symptoms that overlap with B12-deficiency anaemia. A blood test distinguishes them.

Folate is widely distributed in plant foods, particularly pulses and dark green leaves. Values per 100g come from USDA SR Legacy and McCance and Widdowson 7th edition; the site's food entries currently store macros only.

Cooking note: folate is degraded by heat and is water-soluble. Long boiling and discarding the cooking water removes a substantial proportion. Steaming, microwaving, brief stir-frying, or eating raw retains more.

UK fortification: the Department of Health and Social Care confirmed in 2021 that non-wholemeal wheat flour will be fortified with folic acid. This adds folic acid to most UK white and brown breads, in flour-based products, and in bagged flour for home baking. It is a baseline measure to support unplanned pregnancies and does not replace the 400 microgram folic acid supplement for women planning or in early pregnancy.

UK Reference Nutrient Intake (RNI) for folate is set by SACN (1991 Dietary Reference Values).

Folate deficiency causes a specific anaemia (megaloblastic anaemia: large, immature red blood cells). The symptoms develop gradually and look like B12 deficiency, because the two nutrients work together in the same pathway. A blood test for both folate and B12 distinguishes them.

Symptoms:

• Tiredness, lack of energy
• Breathlessness
• Headache
• Palpitations
• Pale skin
• Sore mouth or red, sore tongue (glossitis)
• Mouth ulcers
• Changes in mood, behaviour, or memory

In pregnancy: low folate is associated with neural tube defects in the baby (spina bifida and anencephaly are the main ones). This is why supplementation is recommended before pregnancy and through to 12 weeks, when the neural tube closes.

Who is at higher risk in the UK

• Women planning a pregnancy, or who could become pregnant. See the supplements section for the standing NHS guidance.
• People with coeliac disease, Crohn's, ulcerative colitis, or after gastric surgery. Absorption is reduced.
• People taking certain medicines: some anti-epilepsy drugs, methotrexate, sulfasalazine, and trimethoprim can lower folate. Discuss with the prescriber.
• Heavy alcohol use. Reduces absorption and increases urinary loss.
• People with sickle cell disease or thalassaemia. Higher folate requirement; routine supplementation is part of care.
• Older adults with limited diet variety.
• People with very narrow diets.

When to see your GP: persistent fatigue, breathlessness, mouth changes, or palpitations, especially in a risk group. The blood test that distinguishes folate from B12 deficiency is straightforward, and both are corrected with treatment if confirmed.

Folate from food is not a realistic risk. The risk from supplements is twofold: side effects at very high dose, and the masking of vitamin B12 deficiency.

NHS supplement guidance: taking 1mg (1,000 micrograms) or less a day of folic acid from supplements is unlikely to cause harm in most people.

The B12 masking risk: taking doses of folic acid higher than 1mg a day can mask the early blood-test signs of vitamin B12 deficiency. Folic acid corrects the anaemia (the easy-to-spot blood change) but does not correct the nervous system damage that B12 deficiency causes. The nerve damage can progress silently and become permanent. This is why doses above 1mg are reserved for specific situations on medical advice (see supplements section).

For most women in the standard 400 microgram pregnancy regimen, the masking risk does not arise: 400 micrograms is well below the 1mg threshold.

Some people report mild side effects from supplementation at any dose: stomach upset, sleep disturbance, irritability, skin reactions. These usually settle on stopping.

This is the section where the supplement guidance is unusually specific. Source: NHS.

If you are pregnant, trying to conceive, or could become pregnant

Take a 400 microgram folic acid tablet every day, from before you become pregnant and until you are 12 weeks pregnant. The tablet helps prevent neural tube defects, including spina bifida. It is the standing NHS recommendation.

The 12-week cut-off is because the neural tube closes by the end of the first trimester. Continuing folic acid beyond 12 weeks is not necessary for the protective effect on neural tube defects, though some prenatal supplements do continue with a low dose throughout pregnancy and that is also fine.

Women advised a higher 5mg daily dose (on medical advice)

Some women are advised to take 5 milligrams (5mg) of folic acid every day until 12 weeks of pregnancy, instead of the 400 microgram dose. The NHS lists these groups. Speak to a GP if any of the following apply to you:

• You or your partner have a neural tube defect.
• You or your partner have a family history of neural tube defects.
• You have had a previous pregnancy affected by a neural tube defect.
• You have diabetes.
• You take anti-epilepsy medicine.
• You take anti-retroviral medicine for HIV.
• You have a body mass index (BMI) of 30 or above.
• You have sickle cell disease or thalassaemia, or are a carrier.

The 5mg dose is a prescription dose and is started by a GP. Do not self-prescribe a 5mg dose.

Other situations where folic acid supplements are used

• Confirmed folate deficiency anaemia. Treatment dose under GP supervision, typically 5mg daily for several months.
• Sickle cell disease, thalassaemia, and some other haemolytic anaemias. Long-term lower-dose folic acid is part of routine care.
• People on methotrexate for rheumatoid arthritis, psoriasis, or related conditions: their prescriber arranges folic acid alongside, on a specific schedule.

The standing NHS Healthy Start advice

Qualifying pregnant women and women with children under 4 can receive free Healthy Start vitamins, which contain folic acid, vitamin C, and vitamin D for women, and vitamins A, C, and D for children. This sits alongside the 400 microgram folic acid recommendation for early pregnancy.

• The B12 link: Vitamin B12. Folate and B12 work in the same pathway; high-dose folic acid can mask early B12 deficiency.
• Iron in pregnancy and women's nutrition: Iron.
• Plant-based diets and folate: Plant-based eating. Folate is one of the nutrients vegan diets tend to do well on, with pulses and dark greens.
• Best food sources: Lentils, Chickpeas, Asparagus, Spinach, Broccoli, Avocado, Orange.

• NHS. Vitamins and minerals: Vitamins B. nhs.uk/conditions/vitamins-and-minerals/vitamin-b. Folate and folic acid RNI, supplement upper, B12 masking.
• NHS. Vitamins and supplements: Vitamins, supplements and nutrition in pregnancy. The 400 microgram folic acid recommendation, the 5mg higher-dose list, the 12-week cut-off.
• NHS. Folate deficiency anaemia. Symptoms, causes, treatment.
• SACN. Dietary Reference Values for Food Energy and Nutrients for the United Kingdom. Department of Health Report 41 (1991).
• Department of Health and Social Care. Adding folic acid to non-wholemeal wheat flour: government response, 20 September 2021.
• NHS. Healthy Start scheme.
• Public Health England. McCance and Widdowson's The Composition of Foods, 7th summary edition (2015).

This page is reference information for UK shoppers. It is not medical advice. Pregnancy and pre-pregnancy supplement decisions, particularly the 5mg higher-dose folic acid, should be discussed with a GP.