The principal form of supplementary folate is folic acid. Folate triglutamate (pteroyltriglutamate) is also available. Folic acid is available in single ingredient and in combination products. A typical daily dose is 400 micrograms. Unit doses of one milligram or greater require a prescription. The best way to get enough folic acid is to take a multivitamin with 400 micrograms of folic acid in it and eat a healthy diet. The recommended dietary allowances (RDA) for folate is 400 mcg per day for adults, 600 mcg per day for pregnant women, and 500 mcg for nursing women. Medicinal dosages of up to 1,000-2,000 mcg per day may be prescribed. Women with a history of neural tube sefects need a higher daily allowance of folic acid, 4,000 micrograms. Because of the difference in absorption efficiency between natural food folate and folic acid, the concept of dietary folate equivalents (DFEs) has been introduced. Folic acid taken on an empty stomach is twice as available as food folate. Folic acid taken with food is 1.7 times as available as food folate. For example, 400 micrograms of folic acid taken on an empty stomach is equivalent to 470 micrograms of folic acid taken with food and is equivalent to 800 micrograms of food folate. Folic acid supplementation should always include vitamin B12 supplementation (400 to 1000 mcg daily) because folic acid can mask an underlying vitamin B12 deficiency, which can cause permanent damage to the nervous system.
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