Folic acid, sometimes referred to as folate or vitamin B9 is one of the B vitamins used mainly in childbearing age in order to prevent neural tube defects (NTDs). .
It is crucial to know that conversion from folic acid, folates and other folic acid metabolites to an active form: 5-methyltetahydrofolate (5-MTHF) vary significantly
This article will go over the common functions in the body, dietary sources, chemical difference between different forms of folic acid, health concerns and daily recommendations.
Accurate level of 5-MTHF (active form of folic acid) is essential to :
- synthesize DNA, RNA and for repair process
- support normal cell division and growth
- produce normal red blood cells (it is used to treat megaloblastic anemia – abnormal red blood cells)
- regulate spermatogenesis (improve sperm counts, motility, and decreased numbers of abnormal forms)
- prevent major birth abnormalities (neural tube defects, including sping bifida and anencephaly)
- maintain brain function (neurotransmiters)
Folate deficiency can be caused by :
- gastrointestinal disorders (Crohn's disease, ulcerative colitis, coeliac disease)
- excessive alcohol consumption
- some genetic disorders
- certain medicine usage (phentoin, sulfasalazine, trimethoprim-sulfamethoxazole)
The main sympthoms of deficiency include: glossitis, diarrhea, depression, confusion, anemia, fatigue, headaches, gray hair, mouth sores, poor growth and birth abnormalities.
Folate deficiency can also increase the likelihood of having a premature or low-birth-weight baby .
It can be diagnosed by examining complete blood count, vitamin B12 and serum folate levels, however measuring erythrocyte folate level (140 μg/L or lower) indicates deficiency more clearly.
Folate deficiency is treated by oral supplementation of 400-1000 μg folates per day.
There is a homeostasis between folic acid, vitamin B12 and iron, a deficiency in one can be masked by the excess of another one and they must always be in balance .
What is NTD?
Neural tube defects (NTDs) are common and devastating congenital malformations of the central nervous system. The most common (>90% of cases) are:
- ancephaly (a total or partial absence of brain tissue, skull, and overlying skin)
- sping bifida (herniation of spinal cord, meninges, or both through a defect of spine)
Both arises from incomplete closure of neural tube earlhy in gestation, often even before a woman is aware about pregancy, and this is why it is so improtant to prevents NTDs in all women in childbearing age by maintaining an accurate folate status .
Does diet provide a sufficient folate?
Folates naturally present in food are 50% bioavailable compared to synthetic folic acid or used in food fortification. The reason being are the factors :
- food matrix sometimes bound folates and make them unavailable to retrieve
- losses occured during food harvesting and processing (losses 50-89% after thermal processing)
- poor stability of folates in the food (green vegetables)
- effectiveness of intestinal deconjugation of polyglutamyl folates
Common folic acid found in supplements and fortified food is the most oxidised, monoglutamate form of folate was considered being the most bioavailable, however newer studies have shown that food folates can be almost as effective as folic acid supplements at improving folate status .
However to adjust the those differences between natural folates and syntetic folic acid, there were defined Dietary Folate Equivalents (DFE) are calculated as follows:
1 mcg of dietary folate = 1 mcg of food folate = 0.5 mcg of folic acid taken in the fasting state (the most potent) = 0.6 mcg of folic acid taken with food.
The highest folates source include:
|Beef liver, braised, 3 oz||215|
|Spinach, boiled, 1/2 cup||131|
|Black-eyed peas, boiled, 1/2 cup||105|
|Breakfast cereal, fortified||100|
|Asparagus, boiled, 4 spears||89|
|Brussels sprouts, frozen, boiled, 1/2 cup||78|
|Lettuce, romaine, shredded, 1 cup||64|
|Avocado, raw, sliced, 1/2 cup||59|
|Spinach, raw, 1 cup||58|
|Broccolli, chopped, frozen, cooked, 1/2 cup||52|
Many countries require their manufactures to enhance with folic acid at least one major cereal grain (mainly wheat).
The benefit of the introduction of mandatory folic acid has been demonstrated in the USA since 1998 as a reduction in neural tube defect birth.
However doubt have arised, because actual level of fortification is likeley to have over twice the amount mandated .
Fortification is controversial, not only because of individual liberty, but health concerns of long term health effect on society, especially when synthetic folic acid form is being used .
76 countries in the world mandatory (including: USA, Canada, Australia) add folic acid to cereal grain. No European Union country (as of Nov 2013) has mandated folic acid fortification .
How much is good enough?
Women with RBC (erythrocytes) folate levels lower than 150mcg/L were at high risk of a Neural Tube Defects during pregnancy
On the other hand women with levels over 400mcg/L had a 60% risk reduction .
Administration in doses: 100, 200, and 400mcg daily were associated with a 22%, 41% and 47% reduction in NTD risk, respectively.
Some authors suggested that doses over 400mcg offer little further benefit .
Women with a prior history of NTD affected pregnancy, a 4.0 mg daily dose starting at least one month prior to conception and continuing throughout the first trimester is the current United States recommendation .
According to most of recommendations, all women and teen girls at childbearing age who could become pregnant should consume 400mcg of folic acid equivalent daily (which equals 800mg of folates) from supplements, fortified foods, or both in addition to the folates they get naturally from food .
The active form of folic acid are: tetrahydrofolate (THF) and derivatives that perform all biological functions.
Dietary folate is converted into THF in the small intestine, however folic acid must undergo a reduction and methylation in the liver.
In some cases of the genes mutations it is necessary to administer folic acid as a end-product of the cycle: 5-MTHF and monitor folates and vitamin B12 status.
Genes variations and MTHFR polymorphism
MTHFR stands for methylene-tetrahydrofolate reductase.
It is an the last enzyme in the cycle that converts the folate metabolite into the active form called 5-MTHF, or, 5-Methyltetrahydrofolate.
The most common mutations are MTHFR C677T and MTHFR A1298C which can lead to decreased the MTHFR efficiency by 30-70% .
MTHFR C677T mutation is linked with recurrent pregnancy loss (RPL), risk of NTDs in women, male infertility and increased homocysteine level .
Patients with MTHFR deficiency (<1% activity vs controls) who had undetectable level of of cerebrospinal fluid - MTHF responded to treatment of calcium mefolinate (5-methyltetrahydrofolate) in dose of 15-60mg/kg/day resulted in increasment in CSF 5-MTHF as oppose to folic and folinic acid .
In animal studies supplementation Mefolinate (5-methyltetrahydrofolate), but not folic acid, decreases mortality in an animal model of severe methylenetetrahydrofolate reductase deficiency .
Which folates to choose
The forms of methylfolate that are biologically active are :
- L forms
- 6(S) forms
- L-5 forms
- L-Methylfolate Calcium
- Levomefolic Acid
The forms of methylfolate that are NOT biologically active are :
- D forms
- 6(R) forms
5-MTHF is a game changer
Studies have shown that supplementaion as 5-methylotetrahydrofolate ([6S]-5-methylTHF) as calcium salt (Metafolin, Merck Eprova AG, Schaffhausen) is as effective as folic in increasing blood folate indexes and lowering plasma homocysteine 
On top of this it doesn't mask vitamin B12 deficiency, doesn't produce unmetabolized folic acid in the circulation and it may be more efficient supplemntal souce during latation [Houghton 2006].
Some studies have shown that L-5-MTHF is significantly more potent than folic acid (FA) itself and is a better alternative to supplementation of FA especially in countries not applying a fortification program [11, 12].
The biggest advantage of 5-MTHF is that is well absorbed even when gastrointestinal pH is altered, its bioavailability is not affected by metabolic defects (as it is the final, active form of folate metabolites) and it may even have reduced interaction with drugs that inhibit dihydrofolate reductase [9,10].
Folates are water soluble, so the risk of acute toxicity is low, as an excess is regularly flushed out from the body through urine .
There is however growing concern worldwide, that prenatal high folic acid in the presence of low vitamin B12 causes epigenetic changes in the unborn predisposing them to metabolic syndromes, central adiposity and adult diseases such as Type 2 diabetes .
High doses of folic acid might also increase the risk of colorectal cancer and possibly other cancers in some people [4,7].
Unlike natural folates (form found naturally in food i.e. green leafy vegetables and certain supplements) which can be metabolized in the mucosa of small intesitine, folic acid (one of the form found in supplements and fortified foods) must be processed by specific enzyme – dihydrofolate reductase (DHR) in the liver.
This process is relatively slow and inefficient.
Subsequently, high intake of folic acid (supplements, fortified foods) leads to an excess of un-metabolized folic acid which circulate in the blood stream.
Unmetabolized folic acid
Studies have shown that unmetabolized folic acid in plasma reduces Natural Killer cytoxicity (immune system ability to rapidly respond to viral-infected cells and killing cancer cells .
Studies on eldery people have found that unmetabolized folic acid suffer effects of pernicous anemia (vitamin B12 deficiency).
Another study has suggested that mandatory fortification and prevalent supplementation lead to high folates but also unmetabolized concentrations in maternal and fetal circulation which warrant additional investigation of folate excess nad long-term health outcomes of the offspring .
There are a few drugs which can interfere with folic acid such as:
- methotrexate (when taken to treat cancer)
- phenytoin, carbamazepine, valproate (anti-epileptics)
- sulfasalazine (when taken for ulcerative colitis)
If you take any of the above or having long-term pharmacotheraphy consult your pharmacist/doctor prior to folic acid supplementaion .
There are many diffetent forms of folic acid, but we humans seems to have trouble with converting synthetic form of folic acid (used as a supplement or during food fortification).
The unmetabolized folic acid may reduce some immune cell activity (NK), exacerbate vitamin B12 deficiency, and was linked with some forms of colorectal cancer.
The groups which require additional folic acid as a supplement are: women in childbearning age and nursing women (recommended dose: 800mcg/folates/daily – which is equivalent of 400mcg of folic acid/daily – particulary prior to pregnancy and during first trimester).
Current evidence suggest that folate status should be managed by well-balanced diet (naturally occuring folates) and folates supplements (preferably 5-MTHF forms) NOT by using folic acid (check your multivitamin as well), with also taking into consideration other nutrients relationship (iron, vitamin B12 levels).
Everyone else should be able to get plenty of folate in a diet with adequate vegetable consumption and do not need to supplement.
It is crucial to keep the balance between folates, iron and vitamin levels as an excess of one can mask deficency of other one.
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