Folate deficiency is a low level of folate and derivatives in the body. Also known as vitamin B9, folate is involved in adenosine, guanine, and thymidine synthesis (part of DNA synthesis). Signs of folate deficiency are often subtle. Anemia is a late finding in folate deficiency and folate deficiency anemia is the term given for this medical condition. It is characterized by the appearance of large-sized, abnormal red blood cells (megaloblasts), which form when there are inadequate stores of folic acid within the body.
|Folic acid, a precursor of active B9|
Signs and symptomsEdit
Loss of appetite and weight loss can occur. Additional signs are weakness, sore tongue, headaches, heart palpitations, irritability, and behavioral disorders. In adults, anemia (macrocytic, megaloblastic anemia) can be a sign of advanced folate deficiency.
Women with folate deficiency who become pregnant are more likely to give birth to low birth weight premature infants, and infants with neural tube defects. In infants and children, folate deficiency can lead to failure to thrive or slow growth rate, diarrhea, oral ulcers, megaloblastic anemia, neurological deterioration. Microcephaly, irritability, developmental delay, seizures, blindness and cerebellar ataxia can also be observed.
A deficiency of folate can occur when the body's need for folate is increased, when dietary intake or absorption of folate is inadequate, or when the body excretes (or loses) more folate than usual. Medications that interfere with the body's ability to use folate may also increase the need for this vitamin. Some research indicates that exposure to ultraviolet light, including the use of tanning beds, can lead to a folate deficiency. The deficiency is more common in pregnant women, infants, children, and adolescents. It may also be due to poor diet or a consequence of alcoholism.
Additionally, a defect in homocysteine methyltransferase or a deficiency of B-12 may lead to a so-called "methyl-trap" of tetrahydrofolate (THF), in which THF is converted to a reservoir of methyl-THF which thereafter has no way of being metabolized, and serves as a sink of THF that causes a subsequent deficiency in folate. Thus, a deficiency in B-12 can generate a large pool of methyl-THF that is unable to undergo reactions and will mimic folate deficiency.
Folate (pteroylmonoglutamate) is absorbed throughout the small intestine, though mainly in the Jejunum, binding to specific receptor proteins. Diffuse inflammatory or degenerative diseases of the small intestine, such as Crohn's disease, coeliac disease, chronic enteritis or entero-enteric fistulae, may reduce the activity of pteroyl polyglutamase (PPGH), a specific hydrolase required for folate absorption, and thereby leading to folate deficiency.
Some situations that increase the need for folate include the following:
- kidney dialysis
- liver disease
- malabsorption, including celiac disease and fructose malabsorption
- pregnancy and lactation (breastfeeding)
- tobacco smoking
- alcohol consumption
Medications can interfere with folate metabolism, including:
- anticonvulsant medications (such as phenytoin, primidone, carbamazepine or valproate)
- metformin (sometimes prescribed to control blood sugar in type 2 diabetes)
- methotrexate, an anti-cancer drug also used to control inflammation associated with Crohn's disease, ulcerative colitis and rheumatoid arthritis.
- sulfasalazine (used to control inflammation associated with Crohn's disease, ulcerative colitis and rheumatoid arthritis)
- triamterene (a diuretic)
- birth control pills
When methotrexate is prescribed, folic acid supplements are sometimes given with the methotrexate. The therapeutic effects of methotrexate are due to its inhibition of dihydrofolate reductase and thereby reduce the rate de novo purine and pyrimidine synthesis and cell division. Methotrexate inhibits cell division and is particularly toxic to fast dividing cells, such as rapidly dividing cancer cells and the progenitor cells of the immune system. Folate supplementation is beneficial in patients being treated with long-term, low-dose methotrexate for inflammatory conditions, such as rheumatoid arthritis (RA) or psoriasis, to avoid macrocytic anemia caused by folate deficiency. Folate is often also supplemented before some high dose chemotherapy treatments in an effort to protect healthy tissue. However, it may be counterproductive to take a folic acid supplement with methotrexate in cancer treatment.
Cerebral folate deficiencyEdit
Cerebral folate deficiency is when levels of 5-methyltetrahydrofolate are low in the brain as measured in the cerebral spinal fluid despite being normal in the blood. Symptoms typically appear at about five months of age. Without treatment there may be poor muscle tone, trouble with coordination, trouble talking, and seizures. The causes of cerebral folate deficiency include mutations of genes responsible for folate metabolism and transport. Mutations of the SLC46A1 gene that encodes the proton-coupled folate transporter (PCFT) result in CFD syndromes with both systemic folate deficiency and cerebral folate deficiency. Even when the systemic deficiency is corrected by folate, the cerebral deficiency remains and must be treated with folinic acid.
Folate deficiency is diagnosed with a blood test, measured as methyltetrahydrofolate (in practice, "folate" refers to all derivatives of folic acid, but methylhydrofolate is the quasi unique form of "folate" in the blood).
Homocysteine is elevated (5-MTHF is used to convert homocysteine to methionine) as in vitamin B12 deficiency, whereas methylmalonic acid is normal (elevated in vitamin B12 deficiency and vitamin B6 deficiency).
Prevention and treatmentEdit
Folate is found in leafy green vegetables. When cooking, use of steaming, a food steamer, or a microwave oven can help keep more folate content in the cooked foods, thus helping to prevent folate deficiency.
Multi-vitamin dietary supplements contain folate as well as other B vitamins. Folate deficiency during human pregnancy has been associated with an increased risk of infant neural tube defects. NIH guidelines recommend folate supplements to decrease these risks near the time of conception and during the first month of pregnancy.
Studies suggest that insufficient folate and vitamin B12 status may contribute to major depressive disorder and that supplementation might be useful in this condition. The role of vitamin B12 and folate in depression is due to their role in transmethylation reactions, which are crucial for the formation of neurotransmitters (e.g. serotonin, epinephrine, nicotinamides, purines, phospholipids). The proposed mechanism, is that low levels of folate or vitamin B12 can disrupt transmethylation reaction, leading to an accumulation of homocysteine (hyperhomocisteinemia) and to impaired metabolism of neurotransmitters (especially the hydroxylation of dopamine and serotonin from tyrosine and tryptophan), phospholipids, myelin, and receptors. High homocysteine levels in the blood can lead to vascular injuries by oxidative mechanisms which can contribute to cerebral dysfunction. All of these can lead to the development of various disorders, including depression.
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