Folate, also known as vitamin B9, is a water-soluble vitamin that is involved in the synthesis of DNA and RNA.1–3 Folate is needed to break down homocysteine, an amino acid that can be harmful when present in high amounts.1,2,4 Additionally, folate is essential to the production of red blood cells1,4 and the process of cell division, making it a crucial nutrient for periods of rapid growth, such as prenatal and adolescence.1–4
Recommended Intake and Sources
The amount of folate an individual needs varies with age. The National Institutes of Health (NIH) recommends that children aged 14 to 18 years and adults over 18 years of age receive 400µg of dietary folate equivalent (DFE) per day. Pregnant individuals should receive 600µg DFE per day, and lactating individuals should receive 500µg DFE per day.3
Both the NIH and the United States (US) Centers for Disease Control and Prevention (CDC) recommend that individuals of reproductive age who can get pregnant receive at least 400µg DFE per day to reduce the risk of neural tube defects, since about half of all pregnancies in the US are unplanned, and neural tube defects often occur about 3 to 4 weeks after conception.3,5
The CDC recommends that those who have already had a pregnancy involving a neural tube defect take at least 4,000µg of folic acid per day for at least one month before and throughout the first three months of future pregnancies.5
Folate is measured in DFEs because folic acid, the synthetic form of folate that is used in supplements and fortified foods,5 is better absorbed than folate found in food;1,3 as such, less folic acid is required to reach dietary needs, compared to folate. For example, 400µg DFE is equivalent to 400µg of folate and 240µg of folic acid.3
Sources of folate include dark leafy green vegetables (e.g. spinach, mustard greens), broccoli, Brussel sprouts, asparagus, fruits and fruit juices, beans, sunflower seeds, beef liver, and peanuts.1–3 Since 1998, the US Food and Drug Administration (FDA) has required manufacturers to add 140µg folic acid/100g to enriched grain products, which includes breads, cereals, flours, cornmeals, and rice. Folic acid can also be found in multivitamins, prenatal vitamins, and other dietary supplements.2,3
Deficiency and Disease
Insufficient folate intake prior to pregnancy increases the risk of neural tube defects, such as spina bifida and anencephaly.1–3,6,7 In spina bifida, a portion of the spinal cord and surrounding structures form outside the body. In anencephaly, parts of the brain are absent due to improper formation of the brain and skull bones.6 Inadequate folate intake is also associated with low infant birth weight, premature birth, fetal growth retardation, and placental abruption, wherein the placenta separates from the uterus.2,7
Folate deficiency is rare in the US, but it can lead to serious health concerns. Low levels of folate can cause megaloblastic anemia, in which red blood cells are larger and oval-shaped.2,7,8 In some cases, infants are born with the inability to absorb folic acid, which further increases the risk for megaloblastic anemia.8 Symptoms of megaloblastic anemia include weakness, fatigue, pale skin, irritability, decreased appetite, and shortness of breath.2,8
Several factors can contribute to folate deficiency. Excessive alcohol consumption interferes with folate absorption, and poor-quality diets in individuals with alcohol use disorder puts them at even greater risk for folate deficiency.2,3,7,8 Certain malabsorptive disorders, such as celiac disease and inflammatory bowel disease, can inhibit folate absorption.2,3,7,8 Taking certain antiseizure and ulcerative colitis medications can interfere with folate absorption as well.7,8 Other risk factors for folate deficiency include hemolytic anemia, overcooking fruits and vegetables, and kidney dialysis.7
Individuals with a MTHFR polymorphism struggle to convert folate to its active form, 5-methyl-THF; these individuals should take supplements containing 5-methyl-THF in order to prevent folate deficiency.2,3
Although some studies suggest that folate supplementation decreases the risk of cancer, others show that taking high doses of folate or folic acid might promote the progression of cancer, especially colon cancer.1–3 The NIH notes that the effects of folic acid supplementation on cancer risk remain unclear, particularly in individuals with a history of colorectal adenomas.2
Several studies have shown that supplementation with folic acid alone or combined with other B vitamins can reduce the risk of stroke by 12 to 25 percent, with the most notable risk reduction seen in those with lower baseline folate levels.2
Adults 19 years of age or older should not exceed 1,000µg DFE per day, as excessive amounts of folate can hide a vitamin B12 deficiency, which can lead to irreversible neurological damage.1–3
Editor’s note: Please consult with a qualified healthcare professional to determine what kind of folate intake is right for you.
- Harvard T.H. Chan School of Public Health. Folate (folic acid) – vitamin B9. https://www.hsph.harvard.edu/nutritionsource/folic-acid/. Accessed 26 Sep 2022.
- United States National Institutes of Health Office of Dietary Supplements. Folate: fact sheet for health professional. Updated 29 Mar 2021. https://ods.od.nih.gov/factsheets/Folate-HealthProfessional/. Accessed 26 Sep 2022.
- United States National Institutes of Health Office of Dietary Supplements. Folate: fact sheet for consumers. Updated 22 Mar 2021. https://ods.od.nih.gov/factsheets/Folate-Consumer/. Accessed 26 Sep 2022.
- Mount Sinai. Vitamin B9 (folic acid). https://www.mountsinai.org/health-library/supplement/vitamin-b9-folic-acid. Accessed 26 Sep 2022.
- United States Centers for Disease Control and Prevention. Folic acid. Reviewed 15 Jun 2022. https://www.cdc.gov/ncbddd/folicacid/about.html. Accessed 26 Sep 2022.
- Stanford Medicine Children’s Health. Folic acid for a healthy baby. https://www.stanfordchildrens.org/en/topic/default?id=folic-acid-for-a-healthy-baby-134-2. Accessed 26 Sep 2022.
- Cleveland Clinic. Folate deficiency. Reviewed 14 Dec 2021. https://my.clevelandclinic.org/health/diseases/22198-folate-deficiency. Accessed 26 Sep 2022.
- Johns Hopkins Medicine. Folate-deficiency anemia. https://www.hopkinsmedicine.org/health/conditions-and-diseases/folate-deficiency-anemia. Accessed 26 Sep 2022.