Folic Acid – Vitamin B9: Benefits, Needs and Deficiency

What is Folic Acid?

Folic acid (also known as Vitamin B9 or folate) is a water-soluble vitamin belonging to the B vitamin family. While the term folate refers to the naturally occurring form found in foods, folic acid describes the synthetic form used in dietary supplements and fortified foods. The human body cannot produce folic acid on its own and therefore depends on dietary intake or supplementation.

Biological Functions

Folic acid plays numerous vital roles in the body:

• Cell division and growth: Folic acid is essential for DNA synthesis, DNA repair, and cell division. It is particularly indispensable during periods of rapid growth such as pregnancy and early childhood.
• Blood cell formation: Together with Vitamin B12, folic acid is involved in the production of red blood cells.
• Nervous system development: The vitamin is critical for the development of the neural tube in the unborn child.
• Amino acid metabolism: Folic acid participates in the conversion of the amino acid homocysteine to methionine, thereby helping to regulate homocysteine levels in the blood.

Dietary Sources

Folate occurs naturally in many foods. Particularly good sources include:

• Green leafy vegetables (spinach, kale, lettuce, broccoli)
• Legumes (lentils, chickpeas, beans)
• Liver (beef and chicken liver)
• Eggs and dairy products
• Whole grain products and wheat germ
• Oranges and citrus fruits

Important note: Folate is sensitive to heat and light. Gentle cooking methods such as brief steaming or consuming foods raw help preserve the vitamin content.

Recommended Daily Intake

The World Health Organization (WHO) and national health authorities provide the following daily intake recommendations for folate:

• Adults: 300 µg dietary folate equivalents (DFE) per day
• Pregnant women: 550 µg DFE per day
• Breastfeeding women: 450 µg DFE per day
• Children (1–15 years): 120–300 µg DFE per day (depending on age)

Since synthetic folic acid from supplements has higher bioavailability than naturally occurring folate, the concept of dietary folate equivalents (DFE) is used: 1 µg folic acid (supplement) equals approximately 2 µg food folate.

Folic Acid Deficiency

Causes

Folic acid deficiency can result from various factors:

• Poor or unbalanced diet
• Increased demand (pregnancy, breastfeeding, growth phases)
• Malabsorption (e.g., in celiac disease, Crohn's disease, or chronic alcohol use)
• Use of certain medications (e.g., methotrexate, antiepileptic drugs)

Symptoms of Deficiency

• Megaloblastic anemia (a type of anemia involving enlarged, immature red blood cells)
• Fatigue, exhaustion, and difficulty concentrating
• Inflammation of the mucous membranes of the mouth and a reddened tongue
• Elevated homocysteine levels in the blood (a risk factor for cardiovascular disease)
• In pregnant women: increased risk of neural tube defects in the baby (e.g., spina bifida)

At-Risk Groups

• Pregnant women and women planning to conceive
• Older adults
• People with chronic intestinal diseases
• People with high alcohol consumption
• Individuals with certain genetic variants (e.g., MTHFR polymorphism)

Folic Acid During Pregnancy

Adequate folic acid intake before and during pregnancy is critically important. The neural tube of the embryo closes as early as weeks 4 to 6 of pregnancy -- often before the pregnancy is even confirmed. A deficiency during this critical window can lead to serious neural tube defects such as spina bifida (open spine) or anencephaly.

Therefore, the WHO and many gynecological societies recommend beginning supplementation with 400 µg of folic acid per day at least 4 weeks before planned conception and continuing through the first trimester. Women at higher risk (e.g., those who have previously had a pregnancy affected by a neural tube defect) may require a higher dose of up to 4 mg per day.

Supplementation and Toxicity

Folic acid supplements are generally well tolerated. As a water-soluble vitamin, excess amounts are typically excreted through urine. However, intake from supplements should remain within safe limits:

• The European Food Safety Authority (EFSA) sets the tolerable upper intake level (UL) for adults at 1,000 µg of synthetic folic acid per day.
• Very high intakes can mask a Vitamin B12 deficiency, which may lead to neurological damage -- particularly in older adults.
• Some evidence suggests that extremely high doses might promote the growth of pre-existing precancerous cells, though the evidence remains limited.

Interactions with Medications and Nutrients

• Vitamin B12: Folic acid and Vitamin B12 work closely together. A deficiency in one can affect the metabolism of the other.
• Methotrexate: This medication (used in rheumatoid arthritis and cancer treatment) inhibits folate metabolism. Physicians often recommend supplemental folic acid alongside it.
• Antiepileptic drugs: Certain epilepsy medications can lower folate levels.
• Zinc: High doses of synthetic folic acid may inhibit zinc absorption in the intestine.

References

1. World Health Organization (WHO): Guideline -- Daily iron and folic acid supplementation in pregnant women. Geneva: WHO, 2012.
2. EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA): Scientific Opinion on Dietary Reference Values for folate. EFSA Journal, 2014;12(11):3893.
3. Institute of Medicine (US) Standing Committee on the Scientific Evaluation of Dietary Reference Intakes: Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington (DC): National Academies Press, 1998.