Folaatit

Folaatit, also referred to as folate or vitamin B9, are a family of water‑soluble vitamins essential for one‑carbon metabolism. They act as coenzymes in the synthesis of nucleotides required for DNA replication and repair, as well as in the metabolism of certain amino acids and in the regulation of homocysteine levels. The natural forms found in foods are typically polyglutamates, while synthetic folic acid is commonly used in fortified foods and supplements.

In the body, folates undergo enzymatic conversion to different tetrahydrofolate (THF) derivatives that participate in one‑carbon transfer reactions. After ingestion, natural polyglutamates are deconjugated to monoglutamates and absorbed mainly in the small intestine. Folic acid from supplements or fortified foods is reduced and methylated to 5‑methyl‑THF, the predominant circulating form. THF derivatives contribute to processes such as thymidylate synthesis (for DNA) and purine synthesis, as well as the remethylation of homocysteine to methionine.

Dietary sources include leafy green vegetables, legumes, fortified cereals, citrus fruits, and liver. Many countries fortify staple foods with folic acid to reduce neural tube defects during early fetal development. Daily requirements vary by age and condition, but adequate intake is important for healthy cell division and growth.

Deficiency can cause megaloblastic anemia and elevated homocysteine, and in pregnancy it increases the risk of neural tube defects. Risk factors include poor diet, alcoholism, certain medical conditions, and some medications (for example, methotrexate and certain anticonvulsants). Excess folic acid can mask vitamin B12 deficiency and may interact with specific drugs.