Folate/folic acid

last authored: Feb 2015, Valerie Kim
last reviewed: March 2015, Sylvia Blay

 

Introduction

Folate, or folic acid, is also known as the water-soluble B9 vitamin. It is required for the synthesis of nucleic acids, most notably, deoxyribonucleic acid (DNA). Accordingly, it plays a vital role in the production and maintenance of new cells, especially during periods of significant cell division and growth.

 

This essential nutrient must be regularly supplied through dietary intake, or through supplements in its synthetic form as folic acid. Irregularities in folate levels, due to a deficiency or an excess of folic acid consumption, can be indicative of a wide range of illnesses. Thus, studying folate’s functions and sources holds the potential to better understand and treat various diseases.

return to top

 

 

 

Function

Upon consumption, folate facilitates the addition of a methyl group to nitrogenous bases. This essential process in nucleic acid synthesis ensures that cells can divide as needed for growth, repair, and reproduction. Moreover, in conjunction with other vitamins, folate regulates levels of key amino acids and neurotransmitters (Crider et al., 2012).

 

Given its indispensable functions, folate is essential for a range of metabolic activities. During pregnancy, folic acid supplements are recommended for a baby’s healthy development; in particular, a pregnant woman’s increased consumption of folic acid can facilitate the proper growth of the fetal spinal column, thereby decreasing the risk of neural tube defects (Lassi, 2013). This vitamin is also integral in preventing megaloblastic anemia; this disease, which results in poor transport of oxygen, can be diagnosed by measuring the amount of folate in the blood plasma (Ashraf, Cook, Rothberg, & 2008).

return to top

 

 

 

Daily Requirements and Sources

The following table lists recommended amounts established by the American and Canadian Dietary Reference Intakes (Health Canada, 2010).

Age

Male

(ug/day)

Female

(ug/day)

Pregnant

(ug/day)

Lactating

(ug/day)

0- 6 months

65

65

7-12 months

80

80

1-3 years

150

150

4-8 years

200

200

9-13 years

300

300

14-18 years

400

400

600

500

19+ years

400

400

600

500

 

Dark green leafy vegetables, legumes and tropical fruits are all sources of folate. Because folate is a water-soluble vitamin it can be lost when foods are cooked or boiled in water and the water is discarded; therefore, steaming vegetables and using a minimal amount of cooking water is recommended.

 

Table 2 displays the amount of folate in a sample of foods.

Food Item (serving size)

Amount of Dietary Folate (micrograms = ug)

spinach, raw (1 cup / 250 mL)

61 ug

romaine lettuce (1 cup / 250 mL)

80 ug

bok choy, boiled (½ cup / 125 mL)

37 ug

mango, fresh (1 fruit)

29 ug

lentils, cooked (¾ cup / 175 mL)

265 ug

pinto beans, cooked (¾ cup / 175 mL)

218 ug

peanuts, raw (¼ cup / 60 mL)

89 ug

beef liver (75g)

195 ug

 

In addition to naturally occurring folate, some countries fortify certain commonly consumed foods with folic acid because of the nutrient’s health benefits. For example, since 1998 the Government of Canada has required folic acid be added to all white flour, enriched pasta and enriched cornmeal products sold in Canada as a public health strategy to improve dietary intake. Since mandatory folic acid fortification, studies have shown a significant decline in the rates of neural tube defects in Canada (Liu et al, 2004).

 

A folic acid supplement taken on an empty stomach is more potent than when taken with food, or compared to consuming naturally occurring dietary folate. Because of these differing potencies, the unit Dietary Folate Equivalent (DFE) is used to show the amount of the vitamin available in a food, food product or supplement.

1 DFE = 1 μg food folate

1 DFE = 0.6 μg folic acid from fortified food or from a supplement consumed with food

1 DFE = 0.5 μg folic acid from a supplement taken on an empty stomach

return to top

 

 

 

Digestion, Absorption, and Metabolism

While a small amount of this nutrient can be stored primarily in the liver, our supply of this water-soluble vitamin must be regularly supplied through dietary intake. After consumption of food or supplements, the nutrient is transported through the bloodstream, absorbed via intestinal uptake, metabolized in the liver, and excreted through urine (Bailey & Gregory, 1999).

 

It is important to note that with the nutrient’s dependence on liver activity, folate and its reabsorption are negatively affected by alcohol consumption (National Institutes of Health, 2013).

return to top

 

 

 

Deficiency

While the initial symptoms of folate deficiency are fairly mild and subtle, the ultimate outcomes can encompass a wide range of signs and symptoms, including:

The major two consequences of folate deficiency are Neural Tube Defects (NTD) and Megaloblastic Anemia.

 

Neural Tube Defectsinclude spina bifida and anencephaly. They occur when the neural tube fails to close properly during the third and fourth week of pregnancy. Various studies have corroborated the benefits of folic acid supplements in reducing the prevalence of spina bifida (Lassi, 2013). Accordingly, several countries, including Canada and the United States, have mandated that all refined wheat flour products be fortified with this nutrient (Liu, 2004; Oakley & Tulchinsky, 2010).

 

Megaloblastic Anemia is a condition where bone marrow produces abnormally large, immature and dysfunctional erythrocytes (Red Blood Cells) that cannot properly transport oxygen throughout the body (Ashraf, Cook, Rothberg, & 2008). Megaloblastic anemia has several different causes - deficiencies of either folate (vitamin B9) or cobalamin (vitamin B12) are the two most common causes as both vitamins play an essential role in the production of red blood cells.

 

Again, it is important to note that people who struggle with alcoholism are at increased risk for folate deficiency due to both poor dietary intake and inadequate absorption.

return to top

 

 

 

Toxicity

While side effects of folic acid are rare, high doses may cause the following signs and symptoms:

High doses of folic acid can mask a Vitamin B12 deficiency.

Some studies also raise the concern that too much folic acid for too long may exacerbate existing heart problems and risks of cancer (National Institutes of Health, 2013).

 

Table 3 displays the Tolerable Upper Limit established by the Dietary Reference Intakes to account for the potential toxicity of this nutrient (Health Canada, 2010):

Age

Male

(ug/day)

Female

(ug/day)

Pregnant

(ug/day)

Lactating

(ug/day)

0- 6 months

7-12 months

1-3 years

300

300

4-8 years

400

400

9-13 years

600

600

14-18 years

800

800

800

800

19+ years

1000

1000

1000

1000

return to top

 

 

 

Resources and References

Medline Plus

 

Centers for Disease Control and Prevention

 

Ashraf, M.J., Cook, J.R., & Rothberg, M.B. (2008). Clinical Utility of Folic Acid Testing for Patients with Anemia or Dementia. Journal of General Internal Medicine. 23 (6), pp. 824-826. doi: 10.1007/s11606-008-0615-z

 

Bailey, L.B., & Gregory, J.F. (1999). Folate metabolism and requirements. The Journal of Nutrition. 129 (4), pp. 779-82. Retrieved from http://jn.nutrition.org/content/129/4/779.long

 

Crider, K.S., Yang, T.P., Berry R.J., & Bailey, L.B. (2012). Folate and DNA Methylation: A Review of Molecular Mechanisms and the Evidence for Folate’s Role. Advances in Nutrition. 3, pp.21-28. doi: 10.3945/​an.111.000992

 

Health Canada. (2010). Dietary Reference Intakes Tables. Retrieved from http://www.hc-sc.gc.ca/fn-an/alt_formats/hpfb-dgpsa/pdf/nutrition/dri_tables-eng.pdf

 

Lassi, Z.S., Salam, R.A., Haider, B.A., & Bhutta, Z.A. (2013). Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes. The Cochrane Database of Systematic Reviews. 3, pp. 1-71. doi: 10.1002/14651858.CD006896.pub2

 

Liu S, West R, Randell E, Longerich L, Steel O'Connor K, Scott H, Crowley M, Lam A, Prabhakaran V, McCourt C. (2004). A comprehensive evaluation of food fortification with folic acid for the primary prevention of neural tube defects. BMC Pregnancy and Childbirth 4(1):20.

 

McKillop et al. (2002). The effect of different cooking methods on folate retention in various foods that are amongst the major contributors to folate intake in the UK diet. British Journal of Nutrition. 88 (6), pp. 681-8. doi: http://dx.doi.org/10.1079/BJN2002733

 

National Institutes of Health: Office of Dietary Supplements. (2013). Folate: Fact Sheet for Consumers. Retrieved from http://ods.od.nih.gov/factsheets/Folate-Consumer/#h6

 

Oakley, G.P., & Tulchinsky, T.H. (2010). Folic Acid and Vitamin B12 Fortification of Flour: A Global Basic Food Security Requirement. Public Health Reviews. 32 (1), pp. 284-295. Retrieved from http://www.publichealthreviews.eu/upload/pdf_files/7/16_Folic-acid.pdf