Folic Acid

What is folic acid?

According to the NIH Office of Dietary Supplements, folate is a water-soluble B vitamin; it occurs naturally in foods, is added to some foods, and is sold as a supplement. Formerly also called folacin and sometimes vitamin B9, folate is a general term covering the natural folates in food and the forms in supplements and fortified foods (including folic acid). ^[1]

Folic acid is the synthetic member of this family and is the form used in common supplements and fortified foods. In supplements, 5-MTHF (methylfolate, L-methylfolate) may also be found. The NIH emphasizes that these three are separate terms by saying “folate, folic acid, and 5-MTHF are not the same thing.” ^[1]

In the body, folate is needed for cell division, DNA and RNA synthesis, and amino acid metabolism. The NIH estimates the total amount of folate in the body at about 15–30 mg; about half of this is stored in the liver. ^[1]

What is folic acid for?

That the body needs folate and that an additional supplement improves a specific health outcome are separate questions. Folate deficiency can lead to megaloblastic anemia; for this anemia the NIH lists symptoms such as weakness, fatigue, difficulty concentrating, irritability, headache, palpitations, and shortness of breath. Deficiency is also associated with the risk of neural tube defects in pregnancy. ^[1]

The measured effects of folic acid supplementation on specific outcomes can be summarized as follows: supplementation started before pregnancy prevents neural tube defects; it lowers homocysteine level, but this decrease did not reduce the number of heart attacks; a small decrease was seen for stroke. No benefit has been shown in cancer, and results in depression remained conflicting. Details are on the benefits page.

How much folic acid is needed daily?

Reference values vary by organization. In the US Food and Nutrition Board (IOM) values reported by the NIH, the RDA for adults over 19 is 400 µg DFE, 600 µg DFE in pregnancy, and 500 µg DFE in lactation. ^[1] EFSA, on the other hand, sets a Population Reference Intake (PRI) of 330 µg DFE for adults; the value of 600 µg DFE for pregnancy is not a PRI but an adequate intake (AI) level. ^[2]

Why is DFE used? According to the NIH, at least 85% of folic acid is absorbed when taken with a meal, whereas about 50% of natural folate in food is. Therefore 1 µg DFE equals 1 µg of food folate, 0.6 µg of folic acid taken with a meal or in fortified food, or 0.5 µg of folic acid in a supplement taken on an empty stomach. ^[1]

Why is folic acid recommended in and before pregnancy?

The evidence for folic acid in this area rests on the Cochrane review of randomized trials. The review covered five studies (7,391 women; 2,033 with a history of a neural tube defect pregnancy, 5,358 without) and reported that in the first comparison folic acid prevented neural tube defects: RR 0.31 (95% CI 0.17–0.58; 6,708 births, high-quality evidence). In subgroup analyses, the effect was reported not to be affected by differences in dose at 400 µg per day and above or by whether folic acid was given alone or with other vitamins. ^[4]

The same review also reports that folic acid showed no clear effect for cleft lip, cleft palate, congenital heart defects, miscarriage, or other birth defects; the quality of evidence for these results was rated low or moderate. ^[4]

In Türkiye, the Ministry of Health’s (T.C. Sağlık Bakanlığı) Prenatal Care Management Guideline (2026) finds daily folic acid of 400–800 µg appropriate for every woman planning pregnancy, starting at least 1 month before pregnancy, and states that support be continued in all pregnant women until week 12 of pregnancy. The guideline states that in groups at high risk for neural tube defects, such as those using antiepileptic medicines, those with a history of a neural tube defect pregnancy, and those with diabetes and obesity, a high dose (4–5 mg/day) of folic acid started 3 months before pregnancy is used; this is a separate situation from the general recommendation of 400–800 µg. ^[6]

Which foods contain folic acid?

Folate is found in many foods such as dark green leafy vegetables, legumes, liver, fruits and fruit juices, nuts, eggs, dairy products, and grains. The NIH lists spinach, liver, asparagus, and Brussels sprouts among the foods with the highest folate content. ^[1]

Folate in foods is sensitive to heat, water, and light; the detailed serving table, cooking losses, and fortified products are covered on a separate page.

Who gets folic acid deficiency?

Among groups at high risk of folate inadequacy, the NIH lists women who could become pregnant, pregnant women, people with alcohol use disorder, people with malabsorption such as celiac disease and inflammatory bowel disease, and people carrying the MTHFR 677C>T variant; the MTHFR topic is covered on a separate page. Alcohol is reported to impair folate absorption and retention in the liver, accelerate its breakdown, and increase its excretion in urine. ^[1]

These group definitions are the NIH’s assessment based on US data. Megaloblastic anemia is the main finding of both folate and B12 deficiency; weakness and fatigue, on the other hand, are also seen in many other conditions. Deficiency therefore cannot be diagnosed from symptoms; differentiation rests on a blood count and folate and B12 measurements. ^[1]

The debate about folic acid in supplements and fortified foods being found in the blood as “unmetabolized folic acid,” and the findings of the 2026 systematic review, are covered on the folate versus folic acid comparison page.

How is folate read on a supplement label?

The phrase “folate” or “folic acid” on a label does not describe the amount by itself; it gains meaning together with amount, unit, and form. The NIH reports that on US labels the amount of folate must be written in µg DFE, and if folic acid is added, also in parentheses as µg folic acid, and that the daily value (DV) for folate in adults is 400 µg DFE. Therefore 400 µg DFE and 400 µg folic acid are not the same amount: the latter corresponds to roughly 680 µg DFE when taken with a meal. ^[1]

If a product contains a 5-MTHF salt, EFSA’s 2023 upper limit applies to the combined intake of folic acid and approved 5-MTHF salts. When more than one product is used on the same day (for example, a pregnancy vitamin and a separate folic acid product), the amounts are added together. ^[3]

Excess, the B12 warning, and drug interactions

The NIH reports the adult tolerable upper intake level (UL) for folic acid in supplements and fortified foods as 1,000 µg per day; no UL has been established for natural folate in food, because high folate intake from food has not been reported to cause harm. The UL does not apply to those taking high doses under medical supervision. ^[1] In 2023 EFSA kept the UL values unchanged: 1,000 µg per day in adults, including pregnant and breastfeeding women. The critical effect on which EFSA bases the UL is the risk of progression of neurological symptoms in people with B12 deficiency. ^[3]

The relationship with B12 deficiency is summarized as follows: a high amount of folate can correct the anemia but does not correct the nerve damage of B12 deficiency. The concern has therefore been raised that B12 deficiency could be masked until nerve damage becomes permanent; according to the NIH, questions about this possibility continue, and the focus of the concern has shifted toward the possibility that a high amount of folate may trigger or worsen the anemia and cognitive symptoms due to B12 deficiency. ^[1]

For drug interactions, the NIH reports the following: methotrexate is a folate antagonist, and in patients using it for cancer treatment, folate supplementation can impair the effect of methotrexate; antiepileptics such as phenytoin, carbamazepine, and valproate can lower serum folate level, and folate supplementation can lower the blood level of these medicines; sulfasalazine suppresses folate absorption. In each of these situations, the use of folate is evaluated together with the physician who prescribes the medicine. ^[1]

Folic acid, folate, or methylfolate?

The NIH reports that the bioavailability of 5-MTHF in supplements is equal to or higher than that of folic acid. ^[1] The evidence for preventing neural tube defects comes from studies with folic acid; the “better” claim for methylfolate, claims about the MTHFR variant, and marketing language are covered on a separate page. ^[4]

Fortification and the general situation in Türkiye

In the Türkiye profile of the Food Fortification Initiative, fortification legislation for wheat, maize, and rice is listed as “None.” This database belongs to a civil society initiative and is not an official Turkish document; even so, that no mandatory flour fortification regulation is visible is a different situation from countries that apply mandatory fortification (such as the US). Intake data from these countries therefore cannot be carried directly over to Türkiye. ^[8]

Evidence table: claim, population and limits

Common misunderstandings about folic acid

• “Starting after a positive pregnancy test is enough.” Recommendations are based on starting before pregnancy; the Ministry of Health (T.C. Sağlık Bakanlığı) guideline states starting at least 1 month in advance. ^[6]
• “The more, the better.” In the Cochrane review, the effect on neural tube defects did not vary with dose at 400 µg and above; for amounts above the upper limit, the NIH and EFSA report reservations relating to B12. ^{[4] [3]}
• “Folic acid protects the heart.” Homocysteine falls, but in the Cochrane review the rates of heart attack and death did not change. ^[5]
• “Folate in food and a supplement are the same.” They are not the same; absorption rates differ, which is why reference values are in DFE. ^[1]

This guide does not recommend personal doses. If there is a pregnancy plan, chronic disease, or medicine use, the amount and duration of folic acid are determined with the health professional managing the medicine and pregnancy follow-up.