Folic Acid (Vitamin B9)

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    Katie Jantz

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    Nick Milazzo
    Last Updated: January 30, 2023

    Folic acid is a synthetic form of folate, an essential B vitamin, found in dietary supplements and fortified foods. Folic acid reduces the risk of neural tube defects (NTDs) when used in early pregnancy, treats certain types of anemia, and reduces levels of homocysteine, the latter of which may be linked to beneficial cardiovascular effects.

    Overview

    Dosage information

    Folic acid is most often taken at a dosage of 400 to 800 micrograms (μg), i.e., 0.4 to 0.8 mg, daily. The tolerable upper intake level (UL) of folic acid is 1,000 μg (1 mg) daily. This represents the maximum daily dose unlikely to cause adverse effects and was set based on the concern of folic acid masking vitamin B12 deficiency.[1] In some circumstances, a higher dosage may be warranted.

    For the prevention of NTDs during pregnancy, folic acid can be dosed at 400 μg (0.4 mg) daily, ideally starting a minimum of 4 weeks before conception and continuing until at least the end of the first trimester. In women with a previous pregnancy affected by NTDs, the recommended dose may be much higher (4 to 5 mg daily).[2]

    For reducing homocysteine levels, the maximum benefit can be achieved with folic acid 800 μg (0.8 mg) daily.[3]

    When used for depression in addition to antidepressant medication, the best evidence currently suggests a dose of L-methylfolate 15 mg daily.[4][5]

    For reducing the side effects of low-dose methotrexate (as used for some autoimmune conditions), a dosage of 500 to 1000 μg (0.5 to 1 mg) daily appears to be effective.[6]

    The recommended daily allowance (RDA) of folate for adults is 400 μg dietary folate equivalents (DFEs) daily, as per the Institute of Medicine. This represents the average amount of folate that is thought to meet the nutritional requirements of most healthy people. Natural dietary folate has a lower bioavailability than folic acid, so DFEs are used to convert between the two. For example, 1 μg of dietary folate (1 DFE) is approximately equal to 0.6 μg (taken with food) or 0.5 μg (taken without food) of folic acid. So, to get 400 μg DFEs entirely from supplementation, you would need to take approximately 200 to 240 μg of folic acid.[7]

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    Examine Database References

    1. Depression Symptoms - Taylor MJ, Carney S, Geddes J, Goodwin GFolate for depressive disordersCochrane Database Syst Rev.(2003)
    2. Depression Symptoms - Godfrey PS, Toone BK, Carney MW, Flynn TG, Bottiglieri T, Laundy M, Chanarin I, Reynolds EHEnhancement of recovery from psychiatric illness by methylfolateLancet.(1990 Aug 18)
    3. Schizophrenia symptoms - Sakuma K, Matsunaga S, Nomura I, Okuya M, Kishi T, Iwata NFolic acid/methylfolate for the treatment of psychopathology in schizophrenia: a systematic review and meta-analysis.Psychopharmacology (Berl).(2018-Aug)
    4. Schizophrenia symptoms - Chen CH, Chiu CC, Chiu YH, Chang CH, Chang YH, Huang MC, Lu ML, Chen PYFolate and vitamin B12 supplementation in patients with schizophrenia and low serum folate level: A 24-week randomized, double-blind, placebo-controlled study.J Formos Med Assoc.(2024 Dec 7)
    5. Serum Folate - Duffy ME, Hoey L, Hughes CF, Strain JJ, Rankin A, Souverein OW, Dullemeijer C, Collings R, Hooper L, McNulty HBiomarker responses to folic acid intervention in healthy adults: a meta-analysis of randomized controlled trials.Am J Clin Nutr.(2014-Jan)
    6. TNF-Alpha - Zargarzadeh N, Severo JS, Pizarro AB, Persad E, Mousavi SMThe Effects of Folic Acid Supplementation on Pro-inflammatory Mediators: a Systematic Review and Dose-Response Meta-Analysis of Randomized Controlled Trials.Clin Ther.(2021-Dec)
    7. HbA1c - Sudchada P, Saokaew S, Sridetch S, Incampa S, Jaiyen S, Khaithong WEffect of folic acid supplementation on plasma total homocysteine levels and glycemic control in patients with type 2 diabetes: a systematic review and meta-analysis.Diabetes Res Clin Pract.(2012-Oct)
    8. Seizure Frequency - Ranganathan LN, Ramaratnam SVitamins for epilepsy.Cochrane Database Syst Rev.(2005-Apr-18)
    9. Infant Birth Weight - Fekete K, Berti C, Trovato M, Lohner S, Dullemeijer C, Souverein OW, Cetin I, Decsi TEffect of folate intake on health outcomes in pregnancy: a systematic review and meta-analysis on birth weight, placental weight and length of gestation.Nutr J.(2012-Sep-19)
    10. Infant Birth Weight - Saccone G, Berghella VFolic acid supplementation in pregnancy to prevent preterm birth: a systematic review and meta-analysis of randomized controlled trials.Eur J Obstet Gynecol Reprod Biol.(2016-Apr)
    11. Neural tube defect risk - De-Regil LM, Peña-Rosas JP, Fernández-Gaxiola AC, Rayco-Solon PEffects and safety of periconceptional oral folate supplementation for preventing birth defects.Cochrane Database Syst Rev.(2015-Dec-14)
    12. Blood Pressure - Tabrizi R, Lankarani KB, Akbari M, Naghibzadeh-Tahami A, Alizadeh H, Honarvar B, Sharifi N, Mazoochi M, Ostadmohammadi V, Fatholahpour A, Asemi ZThe effects of folate supplementation on lipid profiles among patients with metabolic diseases: A systematic review and meta-analysis of randomized controlled trials.Diabetes Metab Syndr.(2018-May)
    13. Monocyte Chemoattractant Protein-1 - Bokayeva K, Jamka M, Banaszak M, Makarewicz-Bukowska A, Adamczak A, Chrobot M, Janicka A, Jaworska N, Walkowiak JThe Effect of Folic Acid Supplementation on Endothelial Function and Arterial Stiffness Markers in Adults: A Systematic Review and Meta-Analysis.Healthcare (Basel).(2023-Sep-13)
    14. Stroke Risk - Zhang N, Zhou Z, Chi X, Fan F, Li S, Song Y, Zhang Y, Qin X, Sun N, Wang X, Huo Y, Li JFolic acid supplementation for stroke prevention: A systematic review and meta-analysis of 21 randomized clinical trials worldwide.Clin Nutr.(2024 Jul)
    15. TNF-Alpha - Jiang Z, Qu H, Chen K, Gao ZBeneficial effects of folic acid on inflammatory markers in the patients with metabolic syndrome: Meta-analysis and meta-regression of data from 511 participants in 10 randomized controlled trials.Crit Rev Food Sci Nutr.(2022-Dec-28)
    16. Body Mass Index (BMI) - Jafari A, Gholizadeh E, Sadrmanesh O, Tajpour S, Yarizadeh H, Zamani B, Sohrabi ZThe effect of folic acid supplementation on body weight and body mass index: A systematic review and meta-analysis of randomized controlled trials.Clin Nutr ESPEN.(2023-Feb)
    17. Seminal Motility - Li X, Zeng YM, Luo YD, He J, Luo BW, Lu XC, Zhu LLEffects of folic acid and folic acid plus zinc supplements on the sperm characteristics and pregnancy outcomes of infertile men: A systematic review and meta-analysis.Heliyon.(2023-Jul)
    18. Blood Pressure - Wang WW, Wang XS, Zhang ZR, He JC, Xie CLA Meta-Analysis of Folic Acid in Combination with Anti-Hypertension Drugs in Patients with Hypertension and Hyperhomocysteinemia.Front Pharmacol.(2017)
    19. Memory - Camellia Akhgarjand, Sara Ebrahimi Mousavi, Zahra Kalantar, Amir Bagheri, Hossein Imani, Hamid Rezvani, Mahmoud Dehghani Ghorbi, Zahra VahabiDoes folic acid supplementation have a positive effect on improving memory? A systematic review and meta-analysis of randomized controlled trialsFront Aging Neurosci.(2022 Nov 28)
    20. Cognition - Wang M, Fang M, Zang WEffects of folic acid supplementation on cognitive function and inflammation in elderly patients with mild cognitive impairment: A systematic review and meta-analysis of randomized controlled trials.Arch Gerontol Geriatr.(2024 Jun 19)