Folate – often (erroneously) referred to as folic acid – is the generic term for more than 100 compounds in the group of water-soluble vitamins. In chemical terms, it concerns pteridine derivatives, which contain a p-aminobenzoic acid and a varying number of the amino acid glutamate groups. Folate is predominantly found in green leafy vegetables which led to its naming (lat. folium: leaf). Of biomedical significance are the following forms:
- Folates. This concerns the folate forms which naturally occur in foods. In the groups bound to the nitrogen atoms 5 and 10 (methyl, methylene, methenyl, formyl and formimino groups), folates differ in the degree of hydration of the pteridine ring and in the length of the glutamate side chain.
- Folic acid is a synthetic compound which is not naturally occurring. It is exceptionally stable and in a dosage range of up to 400 µg is quickly and virtually fully absorbed by the gut wall.
- Tetrahydrofolic acid (THF) is the proper biologically active form of the folates and acts as a coenzyme. It serves as an acceptor and carrier of one-carbon groups (C1 residues), including methyl and methylene groups.
Functions of folic acid
In the form of THF, folic acid is involved in more than 20 metabolic reactions, predominantly in the metabolism of amino and nucleic acids. Folic acid thus contributes to a normal amino acid synthesis and cell division. The vitamin also supports the growth of the maternal tissue during pregnancy where it also plays a role in cell division. Further functions of folic acid include:
- Immune system. The activity of the immune cells is dependent on folic acid. The micronutrient thus plays a part in the normal function of the immune system.
- Homocysteine metabolism. Homocysteine is a metabolic proteolysis product which accrues in the body and damages the cell structures. The breakdown of homocysteine occurs with the help of THF such that folic acid contributes to a normal homocysteine metabolism.
- Mental function. The nervous tissue is sensitive to folic acid. Here folic acid plays a part in normal mental function and contributes to the reduction in tiredness and fatigue.
- Formation of blood. With its significance for nucleic acid metabolism, folic acid contributes towards normal blood formation.
- The availability of various forms of folate is exceptionally variable. Synthetic folic acid in a dosage range of 150-5000 µg is practically fully absorbed. Salts of 5-methyl-THF are also almost fully absorbed. In contrast, in foods, they usually have a limited bioavailability as polyglutamate folates since the glutamate chains need to be enzymatically divided before absorption. This division usually occurs only incompletely such that dietary folate only turns out to be available with an average of around 20 %. To accommodate the varying availabilities of the folates, the requirement and recommendation for folate is stated in so-called folate equivalents. The following applies:
- 1 µg FE = 1 µg dietary folate = 0,5 µg synthetic folic acid
The US Dietary Reference Intakes (DRI) further differentiates between whether the synthetic folic acid is administered on an empty stomach or together with food. The following applies:
- 1 µg FE = 0.5 µg synthetic folic acid (taken on an empty stomach) = span class="nobr">0,6 µg synthetic folic acid (taken as part of a meal).
- Folates are very sensitive to heat and oxygen. Losses of up to 100 % are to be expected in the storing and preparation of food.
Information on production technology
- INTERCELL Pharma processes both folic acid (Pteroylmonoglutamate) and the bioactive 5-methyl-THF formed from folic acid.
The conversion capacity of folic acid to 5-methyl-THF in most people achieves its maximum with a single dose of 400 µg of folic acid. The conversion is still less in carriers of MTHFR-677C→T Polymorphism, a genetically linked form of folic acid utilisation disturbance. The bioactive 5-methyl-THF circumvents this problem; an adequate supply of folate is guaranteed for all people.
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