Folate (Vitamin B9) and Folic Acid: Food Sources, Needs and Safety

Overview

Folate is vitamin B9. MedlinePlus says folate occurs naturally in foods such as green leafy vegetables, citrus fruit and beans, while folic acid is man-made (synthetic) folate found in supplements and added to fortified foods. [1] The NHS says folate helps the body form healthy red blood cells and lowers the risk of birth defects called neural tube defects, such as spina bifida, in unborn babies. [2] The difference between the forms matters for intake limits; see folate vs folic acid vs methylfolate.

If you are pregnant or could become pregnant, talk to your doctor, midwife or pharmacist about folic acid before pregnancy. Official bodies in several countries advise a folic acid supplement for people planning a pregnancy (details below). This page quotes those statements and is not personal advice. [2][3]

Evidence labels used here: established nutritional role / deficiency treatment, evidence in adequately nourished people, mixed, insufficient evidence and marketing claim. "Proper evidence not found" means we searched the sources named and found nothing usable.

Food sources

The NHS lists broccoli, brussels sprouts, leafy greens such as cabbage, kale, spring greens and spinach, peas, chickpeas and kidney beans, liver (avoid liver if pregnant) and breakfast cereals fortified with folic acid. [2] MedlinePlus lists dark green leafy vegetables, dried beans and peas, citrus fruits and juices, and enriched or fortified breads, cereals, flours, cornmeals, pastas and rice. [1] See foods high in folate.

Official intake levels

Published levels for the groups named, not personal advice. Units matter: US and Canadian values use dietary folate equivalents (DFE), and their upper levels apply to folic acid itself, not to food folate. [4] See vitamin units explained and RDA, AI, DV and UL.

Folic acid before and during pregnancy

Official statements differ in wording but agree on the principle. All are for the groups and countries named.

What trials found. A 2015 Cochrane review of 5 trials (7,391 women) found folic acid, alone or with other vitamins and minerals, reduced neural tube defects (risk ratio 0.31, high-quality evidence), including recurrence in women with a previous affected pregnancy. It found no clear effect on cleft lip or palate, heart defects or miscarriage. [7] Subgroup analyses in that review suggested the protection did not differ between 400 mcg a day and higher amounts. [7] See folic acid and folate before and during pregnancy and prenatal vitamins.

Deficiency and who may need assessment

Established. The NHS says folate or B12 deficiency anaemia happens when a lack of these vitamins makes the body produce abnormally large red blood cells that cannot function properly. Symptoms include extreme tiredness, pins and needles, a sore red tongue and mouth ulcers. [8] Causes include a poor diet over a long time (uncommon) and medicines such as anticonvulsants and proton pump inhibitors. It is more common in older people, and the NHS advises seeing a GP because some effects can be permanent if untreated. [8] Treatment, usually folic acid tablets, is led by a clinician after blood tests. [8] See folate deficiency and megaloblastic anemia and folate blood tests.

Safety and precautions

• Masking vitamin B12 deficiency: the NHS says folic acid above 1 mg a day can mask the symptoms of B12 deficiency, which can eventually damage the nervous system if not spotted and treated, and that this is a particular concern for older people. [2] MedlinePlus likewise says higher levels can mask B12 deficiency. [1] The NHS also lists B12 deficiency anaemia among conditions for which folic acid may not be suitable. [9]
• Other conditions: the NHS says folic acid may not be suitable if you have a coronary stent or cancer, and to tell your doctor about medical conditions first. [9]
• Medicines: the NHS lists epilepsy medicines (phenytoin, phenobarbital, primidone), antibiotics (chloramphenicol, co-trimoxazole), sulfasalazine, lithium and aspirin as possible interactions, and notes folic acid is also used to prevent side effects of methotrexate under medical direction. [9] Do not change any prescribed medicine on your own; see medication interactions.
• Side effects: bloating, gas, nausea and loss of appetite; rarely, a serious allergic reaction. [9]
• Too many tablets: the NHS says one extra folic acid dose alone is unlikely to cause problems but too many multivitamin tablets can be dangerous. [9] In the US, call Poison Help at 1-800-222-1222 if someone has swallowed too many; see vitamin overdose in children.
• Children: the NHS says multivitamins containing folic acid are not recommended for children under 12. [9]
• Alcohol: the NHS says it is best to avoid or limit alcohol because it can affect how well folic acid works. [9]
• Kidney and liver conditions, surgery: a 2023 review says kidney disease changes water-soluble vitamin needs and folate supplementation should be managed by the care team. [10] Proper evidence not found specific to surgery; see vitamins before surgery.
• Quality: see quality testing and certifications. On fortification and unmetabolized folic acid see what is known and unknown.

Testing

The NHS says folate deficiency can often be diagnosed from symptoms and a blood test. [8] Results vary by laboratory and country and can be affected by recent diet, illness and medicines. See deficiency testing and its limits.

Related

All vitamins · Vitamin B12 · Understanding vitamins · Vitamins in pregnancy