Vitamin B9/folic acid

The term applies for symbols B10 and B11. Sometimes the term folacin is also used. The biologically active form of folic acid is its coenzyme form tetrahydrofolate (THF), which is also called antianemic vitamin. Folic acid decomposes when exposed to heat and light.

Which foods contain the vitamin?

• Liver
• Wheat germ
• Beans
• Cauliflower
• Strawberry

Biological functions of the vitamin

Realised in the THF form which performs the transfer of single-carbon residue during the synthesis of purines, dTMP, serine, glycine, choline and other biomolecules. The biosynthesis of purines and dTMP are the main processes in the biosynthesis of nucleic acids, which need folic acid.

Folic acid is also necessary for the functioning of brain tissue, development of erythrocytes and the formation of hydrochloric acid in the stomach.

Absorption, storage and excretion

Folic acid is absorbed with active transport in jejunum. Absorption is inhibited by excessive alcohol, smoking, anticonvulsants, phenobarbital and oral contraceptives; streptomycin (antibiotis) decomposes folic acid.

In some extent, folic acid is also produced by the intestinal microflora.

This vitamin is stored in liver in the form of polyglutamate and the reserves last for 1–3 months.

Problems resulting from deficiency

• Irritability
• Diarrhoea
• Memory disorders
• Growth retardation
• Cracked corners of mouth
• Tongue inflammation
• Megaloblastic anaemia
• Homocystinuria

Risk groups for developing the deficiency

• Alcoholics
• People suffering form malnutrition
• Consumers of phenobarbitals, oral contraceptives, anticonvulsants and sulfonamides
• Consumers of methotrexate (immunosuppressant)
• Pregnant and nursing women
• Excessive tanners
• Persons who undergo hemodialysis
• Persons with liver diseases
• Persons with malabsorption syndrome (celiac disease)

Toxicity

Overdose is not possible if administered orally, since the low solubility of riboflavin prevents the absorption of excessive amounts from the digestive system.

Toxic effects are not observed even when administering large doses because kidneys effectively remove excessive amounts of riboflavin. However, it must be noted that continuous administration of large quantities of riboflavin considerably increases the excretion of other B vitamins with urine, which may lead to the deficiency thereof.

Use of vitamin preparations

As an additional treatment component, folic acid may also be used for treating alcoholism, anaemia, pellagra, scurvy, gastritis, psoriasis and chronic haemolytic conditions. Folic acid also has properties preventing stroke, since it lowers blood pressure.

Additional intake is also reasonable during the first trimester of pregnancy (recommended daily amount 0.4–1 mg/day, in case of loaded anamnesis 4–5 mg/day) and when nursing. Pregnant women who take anticonvulsants should especially avoid folic acid deficiency and administer additional doses of folic acid to prevent the risk of neural tube defects, cleft lip and cleft palate, congenital heart defects and congenital urogenital tract defects.

Studies have indicated that the administration of 0.7 mg folate by men reduces the chromosome abberrations in sperm, increasing the possibility of giving birth to a healthy child.

Contraindications

• Any malignant tumor which is diagnosed or in remission or a suspicion of a malignant tumor
• Anaemia with unclear reasons

Figure 1. Vitamin B9: folic acid