VITAMIN B9

CAS Number: 59-30-3
EC Number: 200-419-0
MDL number: MFCD00079305

Properties

Formula: C19H19N7O6
Molar mass: 441.404 g·mol−1
Density: 1.6±0.1 g/cm3 
Melting point: 250 °C (482 °F) (decomposition)
Solubility in water: 1.6mg/L (25 °C)

APPLICATIONS

Vitamin B9 is crucial for proper brain function and plays an important role in mental and emotional health. 
Vitamin B9 aids in the production of DNA and RNA, the body's genetic material, and is especially important when cells and tissues are growing rapidly, such as in infancy, adolescence, and pregnancy. 
Vitamin B9 also works closely with vitamin B12 to help make red blood cells and help iron work properly in the body.

Vitamin B9 works with vitamins B6 and B12 and other nutrients to control blood levels of the amino acid homocysteine. High levels of homocysteine are associated with heart disease, however researchers are not sure whether homocysteine is a cause of heart disease or just a marker that indicates someone may have heart disease.

Vitamin B9 has been used:
-to study the role of vitamins and amino acids on hybridoma growth and monoclonal antibody production
-in cells and treatments
-in perforin gene targeting using the CRISPR/Cas gene editing approach.

Vitamin B9 in the diet seems to protect against the development of some forms of cancer, including:

-Colon cancer
-Breast cancer
-Cervical cancer
-Pancreatic cancer
-Stomach cancer

However, this evidence is based on population studies that show people who get enough Vitamin B9 in their diet have lower rates of these cancers. 
Researchers do not know exactly how Vitamin B9 might help prevent cancer. 
Some think that Vitamin B9 keeps DNA healthy and prevents mutations that can lead to cancer. 
There is no evidence that taking folic acid supplements helps prevent cancer. 
The best course of action is to make sure you eat a balanced diet with enough Vitamin B9, which will help protect you against a number of diseases.

Low dietary intake of Vitamin B9 may increase the risk of developing breast cancer, particularly for women who drink alcohol. 
Regular use of alcohol, more than 1½ to 2 glasses per day, is associated with higher risk of breast cancer. 
One large study, involving more than 50,000 women followed over time, suggests that adequate intake of Vitamin B9 may reduce the risk of breast cancer associated with alcohol.

Folate (vitamin B-9) is important in red blood cell formation and for healthy cell growth and function. 
Vitamin B9 is crucial during early pregnancy to reduce the risk of birth defects of the brain and spine.
Vitamin B9 plays an essential part in producing genetic material (DNA, RNA) and amino acids that are essential for cell growth. 
Also, Vitamin B9 plays a critical role in brain and nervous functions, especially in the synthesis of neurotransmitters (the messengers of nerve cells).

Vitamin B9 is involved in the formation of red blood cells as well as in the immune system, helps heal wounds, and reduces the formation of homocysteine, a molecule which is linked to cardiovascular diseases when found in high levels.

Vitamin B9 is necessary for many bodily functions. Its health benefits include:

-Lower risk of neural tube defects

An adequate amount of Vitamin B9 is essential during pregnancy to help prevent neural tube defects. 
This issue occurs when the neural tube, which forms the early brain and spinal cord, does not close properly. 
This happens in early pregnancy and can result in conditions such as spina bifida or anencephaly.

Vitamin B9 is an essential substance for the human body in the use of sugars and amino acids and is essential for the growth and reproduction of cells in the body.    
Vitamin B9 helps protein metabolism, and together with vitamin B12 promote red blood cell production and maturation, is an indispensable material for the production of red blood cells.    

Vitamin B9 also acts as a promoting factor for growth of Lactobacillus casei and other microorganisms.    
Vitamin B9 is an indispensable nutrient for fetal growth and development. 
The lack of Vitamin B9 in pregnant women may lead to low birth weight, cleft lip and palate, and heart defects at birth. 
If the lack of Vitamin B9 within the first 3 months of pregnancy can cause defects in the fetal neural tube, resulting in deformity.    

Vitamin B9 plays an important role in cell division and growth and synthesis of nucleic acids, amino acids and proteins. 
The lack of Vitamin B9 in the human body can lead to abnormal red blood cells, increased immature cells, anemia, and decreased white blood cells. 

-Lower risk of stroke

According to the National Institutes of Health (NIH), researchers have found that Vitamin B9 supplements lower levels of the amino acid homocysteine. 
High levels of this amino acid are linked to a higher risk of cardiovascular disease and stroke.

While studies have not proven that Vitamin B9 reduces the risk of cardiovascular disease, several have found that higher intake is associated with a lower risk of stroke.

-Possible reduced risk of cognitive decline

Homocysteine is also associated with a higher risk of dementia. 
While studies have not shown that taking Vitamin B9 reduces the risk of dementia in otherwise healthy people, those who are at risk of cognitive decline in older age may benefit from taking it. 
Evidence suggests that Vitamin B9 may help preserve memory and executive function in at-risk groups.

DESCRIPTION

Vitamin B9, also known as folate and folacin, is one of the B vitamins.
Manufactured folic acid, which is converted into Vitamin B9 by the body, is used as a dietary supplement and in food fortification as it is more stable during processing and storage.
Vitamin B9 is required for the body to make DNA and RNA and metabolise amino acids necessary for cell division.
As humans cannot make Vitamin B9, it is required in the diet, making it an essential nutrient. 
Vitamin B9 occurs naturally in many foods. 
The recommended adult daily intake of Vitamin B9 in the U.S. is 400 micrograms from foods or dietary supplements.

Vitamin B9 in the form of folic acid is used to treat anemia caused by vitamin B9 deficiency.
Folic acid is also used as a supplement by women during pregnancy to reduce the risk of neural tube defects (NTDs) in the baby. 
Low levels in early pregnancy are believed to be the cause of more than half of babies born with NTDs. 
More than 80 countries use either mandatory or voluntary fortification of certain foods with folic acid as a measure to decrease the rate of NTDs. 
Long-term supplementation with relatively large amounts of folic acid is associated with a small reduction in the risk of stroke and an increased risk of prostate cancer.
There are concerns that large amounts of supplemental folic acid can hide vitamin B12 deficiency.

Not consuming enough vitamin B9 can lead to Vitamin B9 deficiency. 
This may result in a type of anemia in which red blood cells become abnormally large.
Symptoms may include feeling tired, heart palpitations, shortness of breath, open sores on the tongue, and changes in the color of the skin or hair. 
Vitamin B9 deficiency in children may develop within a month of poor dietary intake. 
In adults, normal total body Vitamin B9 is between 10 and 30 mg with blood levels of greater than 7 nmol/L (3 ng/mL).

Vitamin B9 was discovered between 1931 and 1943. 
It is on the World Health Organization's List of Essential Medicines. 
In 2019, it was the 89th most commonly prescribed medication in the United States, with more than 8 million prescriptions. 
The term "folic" is from the Latin word folium (which means leaf) because it was found in dark-green leafy vegetables.

"Folate" (vitamin B9) refers to the many forms of folic acid and its related compounds, including tetrahydrofolic acid (the active form), methyltetrahydrofolate (the primary form found in blood), methenyltetrahydrofolate, folinic acid, folacin, and pteroylglutamic acid.
Historic names included L. ⁠casei factor, vitamin Bc and vitamin M.

The terms "folate" and "folic acid" have somewhat different meanings in different contexts, although sometimes used interchangeably.
Within the field of organic chemistry, folate refers to the conjugate base of folic acid.
Within the field of biochemistry, folates refer to a class of biologically active compounds related to and including folic acid.
Within the field of nutrition, the "folates" are a family of essential nutrients related to folic acid obtained from natural sources whereas the term "folic acid" is reserved for the manufactured form that is used as a dietary supplement.

Chemically, folates consist of three distinct chemical moieties linked together. 
A pterin (2-amino-4-hydroxy-pteridine) heterocyclic ring is linked by a methylene bridge to a p-aminobenzoyl group that in turn is bonded through an amide linkage to either glutamic acid or poly-glutamate. 
One-carbon units in a variety of oxidation states may be attached to the N5 nitrogen atom of the pteridine ring and/or the N10 nitrogen atom of the p-aminobenzoyl group.

Vitamin B9 is the natural form of vitamin B9, water-soluble and naturally found in many foods. 
Vitamin B9 is also added to foods and sold as a supplement in the form of folic acid; this form is actually better absorbed than that from food sources—85% vs. 50%, respectively. 
Vitamin B9 helps to form DNA and RNA and is involved in protein metabolism. 
Moreover, Vitamin B9 plays a key role in breaking down homocysteine, an amino acid that can exert harmful effects in the body if it is present in high amounts. 
Vitamin B9 is also needed to produce healthy red blood cells and is critical during periods of rapid growth, such as during pregnancy and fetal development.

HEALTH EFFECTS

Vitamin B9 is especially important during periods of frequent cell division and growth, such as infancy and pregnancy. 
Vitamin B9 deficiency hinders DNA synthesis and cell division, affecting hematopoietic cells and neoplasms the most because of their greater frequency of cell division. RNA transcription and subsequent protein synthesis are less affected by Vitamin B9 deficiency, as the mRNA can be recycled and used again (as opposed to DNA synthesis, where a new genomic copy must be created).

Birth defects

Deficiency of Vitamin B9 in pregnant women has been implicated in neural tube defects (NTDs), with an estimate of 300,000 cases worldwide prior to the implementation in many countries of mandatory food fortification.
NTDs occur early in pregnancy (first month), therefore women must have abundant Vitamin B9 upon conception and for this reason there is a recommendation that any woman planning to become pregnant consume a Vitamin B9-containing dietary supplement before and during pregnancy. 

The Center for Disease Control and Prevention (CDC) recommends a daily amount of 400 micrograms of folic acid for the prevention of NTDs. 
Compliance with this recommendation is not complete, and many women become pregnant without this being a planned pregnancy, or may not realize that they are pregnant until well into the first trimester, which is the critical period for reducing risk of NTDs. 
Countries have implemented either mandatory or voluntary food fortification of wheat flour and other grains, or else have no such program and depend on public health and healthcare practitioner advice to women of childbearing age. 

A meta-analysis of global birth prevalence of spina bifida showed that when mandatory fortification was compared to countries with voluntary fortification or no fortification program, there was a 30% reduction in live births with spina bifida. 
Some countries reported a greater than 50% reduction. 
The United States Preventive Services Task Force recommends folic acid as the supplement or fortification ingredient, as forms of Vitamin B9 other than folic acid have not been studied.

A meta-analysis of Vitamin B9 supplementation during pregnancy reported a 28% lower relative risk of newborn congenital heart defects.
Prenatal supplementation with folic acid did not appear to reduce the risk of preterm births.
One systematic review indicated no effect of folic acid on mortality, growth, body composition, respiratory, or cognitive outcomes of children from birth to 9 years old.
There was no relation between maternal folic acid supplementation and an increased risk for childhood asthma.

Fertility

Vitamin B9 contributes to spermatogenesis.
In women, Vitamin B9 is important for oocyte quality and maturation, implantation, placentation, fetal growth and organ development.

Heart disease

One meta-analysis reported that multi-year folic acid supplementation, in amounts in most of the included clinical trials at higher than the UL of 1,000 μg/day, reduced the relative risk of cardiovascular disease by a modest 4%.
Two older meta-analyses, which would not have incorporated results from newer clinical trials, reported no changes to the risk of cardiovascular disease.

Stroke

The absolute risk of stroke with supplementation decreases from 4.4% to 3.8% (a 10% decrease in relative risk).
Two other meta-analyses reported a similar decrease in relative risk. 
Two of these three were limited to people with pre-existing cardiovascular disease or coronary heart disease. 

The beneficial result may be associated with lowering circulating homocysteine concentration, as stratified analysis showed that risk was reduced more when there was a larger decrease in homocysteine. 
The effect was also larger for the studies that were conducted in countries that did not have mandatory grain folic acid fortification.
The beneficial effect was larger in the subset of trials that used a lower folic acid supplement compared to higher.

Cancer

Chronically insufficient intake of Vitamin B9 may increase the risk of colorectal, breast, ovarian, pancreatic, brain, lung, cervical, and prostate cancers.

Early after fortification programs were implemented, high intakes were theorized to accelerate the growth of preneoplastic lesions that could lead to cancer, specifically colon cancer.
Subsequent meta-analyses of the effects of low versus high dietary Vitamin B9, elevated serum Vitamin B9, and supplemental Vitamin B9 in the form of folic acid have reported at times conflicting results. 

Comparing low to high dietary Vitamin B9 showed a modest but statistically significant reduced risk of colon cancer. 
For prostate cancer risk, comparing low to high dietary Vitamin B9 showed no effect, but the same two studies reported a significant increased risk for prostate cancer correlating to elevated serum Vitamin B9.

Two reviews of trials that involved folic acid dietary supplements reported, respectively, a statistically significant 24% increase in prostate cancer risk and a not significant 17% increase in prostate cancer risk.
Supplementation with folic acid at 1,000 to 2,500 μg/day – the amounts used in many of the supplement trials – would result in higher concentrations of serum Vitamin B9 than what is achieved from diets high in food-derived Vitamin B9. 

The second study reported no significant increase or decrease in total cancer incidence, colorectal cancer, other gastrointestinal cancer, genitourinary cancer, lung cancer or hematological malignancies in people who were consuming folic acid supplements.
A third supplementation meta-analysis limited to reporting only on colorectal cancer incidence showed that folic acid treatment was not associated with colorectal cancer risk.

Anti-Vitamin B9 chemotherapy

Vitamin B9 is important for cells and tissues that divide rapidly. 
Cancer cells divide rapidly, and drugs that interfere with Vitamin B9 metabolism are used to treat cancer. 
The antifolate drug methotrexate is often used to treat cancer because it inhibits the production of the active tetrahydrofolate (THF) from the inactive dihydrofolate (DHF).
However, methotrexate can be toxic, producing side effects such as inflammation in the digestive tract that make eating normally more difficult. 
Bone marrow depression (inducing leukopenia and thrombocytopenia) and acute kidney and liver failure have been reported.

Folinic acid, under the drug name leucovorin, a form of Vitamin B9 (formyl-THF), can help "rescue" or reverse the toxic effects of methotrexate.
Folic acid supplements have little established role in cancer chemotherapy. 
The supplement of folinic acid in people undergoing methotrexate treatment is to give less rapidly dividing cells enough Vitamin B9 to maintain normal cell functions. 
The amount of Vitamin B9 given is quickly depleted by rapidly dividing (cancer) cells, so this does not negate the effects of methotrexate.

Neurological disorders

Conversion of homocysteine to methionine requires Vitamin B9 and vitamin B12. 
Elevated plasma homocysteine and low Vitamin B9 are associated with cognitive impairment, dementia and Alzheimer's disease. 
Supplementing the diet with folic acid and vitamin B12 lowers plasma homocysteine. 
However, several reviews reported that supplementation with folic acid alone or in combination with other B vitamins did not prevent development of cognitive impairment nor slow cognitive decline.

A 2017 meta-analysis found that the relative risk of autism spectrum disorders was reduced by 23% when the maternal diet was supplemented with folic acid during pregnancy. 
Subset analysis confirmed this among Asian, European and American populations.

Some evidence links a shortage of Vitamin B9 with clinical depression. 
Limited evidence from randomized controlled trials showed using folic acid in addition to selective serotonin reuptake inhibitors (SSRIs) may have benefits.
Research found a link between depression and low levels of Vitamin B9. 

The exact mechanisms involved in the development of schizophrenia and depression are not entirely clear, but the bioactive Vitamin B9, methyltetrahydrofolate (5-MTHF), a direct target of methyl donors such as S-adenosyl methionine (SAMe), recycles the inactive dihydrobiopterin (BH2) into tetrahydrobiopterin (BH4), the necessary cofactor in various steps of monoamine synthesis, including that of dopamine. 
BH4 serves a regulatory role in monoamine neurotransmission and is required to mediate the actions of most antidepressants. 
5-MTHF also plays both direct and indirect roles in DNA methylation, NO2 synthesis, and one-carbon metabolism.

Folic acid, B12 and iron

A complex interaction occurs between folic acid, vitamin B12, and iron. 
A deficiency of folic acid or vitamin B12 may mask the deficiency of iron; so when taken as dietary supplements, the three need to be in balance.

Malaria

Some studies show iron–folic acid supplementation in children under five may result in increased mortality due to malaria; this has prompted the World Health Organization to alter their iron–folic acid supplementation policies for children in malaria-prone areas, such as India.

BIOSYTNHESIS

Animals, including humans, cannot synthesize Vitamin B9 and therefore must obtain vitamin B9 from their diet. 
All plants and fungi and certain protozoa, bacteria, and archaea can synthesize Vitamin B9 de novo through variations on the same biosynthetic pathway.
The Vitamin B9 molecule is synthesized from pterin pyrophosphate, para-aminobenzoic acid, and glutamate through the action of dihydropteroate synthase and dihydrofolate synthase. 
Pterin is in turn derived in a series of enzymatically catalyzed steps from guanosine triphosphate (GTP), while para-aminobenzoic acid is a product of the shikimate pathway.

BIOACTIVATION

All of the biological functions of folic acid are performed by THF and its methylated derivatives. 
Hence folic acid must first be reduced to THF. 
This four electron reduction proceeds in two chemical steps both catalyzed by the same enzyme, dihydrofolate reductase. 
Folic acid is first reduced to dihydrofolate and then to tetrahydrofolate. 

Each step consumes one molecule of NADPH (biosynthetically derived from vitamin B3) and produces one molecule of NADP. 
Mechanistically, hydride is transferred from NADPH to the C6 position of the pteridine ring.
A one-carbon (1C) methyl group is added to tetrahydrofolate through the action of serine hydroxymethyltransferase (SHMT) to yield 5,10-methylenetetrahydrofolate (5,10-CH2-THF). 

This reaction also consumes serine and pyridoxal phosphate (PLP; vitamin B6) and produces glycine and pyridoxal. 
A second enzyme, methylenetetrahydrofolate dehydrogenase (MTHFD2) oxidizes 5,10-methylenetetrahydrofolate to an iminium cation which in turn is hydrolyzed to produce 5-formyl-THF and 10-formyl-THF. 
This series of reactions using the β-carbon atom of serine as the carbon source provide the largest part of the one-carbon units available to the cell.

Alternative carbon sources include formate which by the catalytic action of formate–tetrahydrofolate ligase add a 1C unit to THF to yield 10-formyl-THF. 
Glycine, histidine, and sarcosine can also directly contribute to the THF-bound 1C pool.

DRUG INTERFERENCE 

A number of drugs interfere with the biosynthesis of THF from folic acid. 
Among them are the antifolate dihydrofolate reductase inhibitors such as the antimicrobial, trimethoprim, the antiprotozoal, pyrimethamine and the chemotherapy drug methotrexate, and the sulfonamides (competitive inhibitors of 4-aminobenzoic acid in the reactions of dihydropteroate synthetase).

Valproic acid, one of the most commonly prescribed epilepsy treatment drugs, also used to treat certain psychological conditions such as bipolar disorder, is a known inhibitor of folic acid, and as such, has been shown to cause birth defects, including neural tube defects, plus increased risk for children having cognitive impairment and autism. There is evidence that vitamin B9 consumption is protective.

FUNCTION

Tetrahydrofolate's main function in metabolism is transporting single-carbon groups (i.e., a methyl group, methylene group, or formyl group). 
These carbon groups can be transferred to other molecules as part of the modification or biosynthesis of a variety of biological molecules. 
Folates are essential for the synthesis of DNA, the modification of DNA and RNA, the synthesis of methionine from homocysteine, and various other chemical reactions involved in cellular metabolism. 
These reactions are collectively known as folate-mediated one-carbon metabolism.

DNA SYNTHESIS

Vitamin B9 derivatives participate in the biosynthesis of both purines and pyrimidines.
Formyl folate is required for two of the steps in the biosynthesis of inosine monophosphate, the precursor to GMP and AMP. Methylenetetrahydrofolate donates the C1 center required for the biosynthesis of dTMP (2′-deoxythymidine-5′-phosphate) from dUMP (2′-deoxyuridine-5′-phosphate). 
The conversion is catalyzed by thymidylate synthase.

DIETARY RECOMMENDATIONS 

Because of the difference in bioavailability between supplemented folic acid and the different forms of vitamin B9 found in food, the dietary vitamin B9 equivalent (DFE) system was established. 
One DFE is defined as 1 μg of dietary vitamin B9. 
1 μg of folic acid supplement counts as 1.7 μg DFE. 
The reason for the difference is that when folic acid is added to food or taken as a dietary supplement with food it is at least 85% absorbed, whereas only about 50% of vitamin B9 naturally present in food is absorbed.

The U.S. Institute of Medicine defines Estimated Average Requirements (EARs), Recommended Dietary Allowances (RDAs), Adequate Intakes (AIs), and Tolerable upper intake levels (ULs) – collectively referred to as Dietary Reference Intakes (DRIs). 
The European Food Safety Authority (EFSA) refers to the collective set of information as Dietary Reference Values, with Population Reference Intake (PRI) instead of RDA, and Average Requirement instead of EAR. 
AI and UL are defined the same as in United States. 

For women and men over age 18 the PRI is set at 330 μg/day. 
PRI for pregnancy is 600 μg/day, for lactation 500 μg/day. 
For children ages 1–17 years the PRIs increase with age from 120 to 270 μg/day. 
These values differ somewhat from the U.S. RDAs.
The United Kingdom's Dietary Reference Value for vitamin B9, set by the Committee on Medical Aspects of Food and Nutrition Policy in 1991, is 200 μg/day for adults.

SAFETY

The risk of toxicity from folic acid is low because vitamin B9 is a water-soluble vitamin and is regularly removed from the body through urine. 
One potential issue associated with high doses of folic acid is that it has a masking effect on the diagnosis of pernicious anaemia due to vitamin B12 deficiency, and may even precipitate or exacerbate neuropathy in vitamin B12-deficient individuals. 
This evidence justified development of a UL for vitamin B9.

In general, ULs are set for vitamins and minerals when evidence is sufficient. 
The adult UL of 1,000 μg for vitamin B9 (and lower for children) refers specifically to folic acid used as a supplement, as no health risks have been associated with high intake of vitamin B9 from food sources. 
The EFSA reviewed the safety question and agreed with United States that the UL be set at 1,000 μg. 
The Japan National Institute of Health and Nutrition set the adult UL at 1,300 or 1,400 μg depending on age.

Reviews of clinical trials that called for long-term consumption of folic acid in amounts exceeding the UL have raised concerns. 
Excessive amounts derived from supplements are more of a concern than that derived from natural food sources and the relative proportion to vitamin B12 may be a significant factor in adverse effects. 
One theory is that consumption of large amounts of folic acid leads to detectable amounts of unmetabolized folic acid circulating in blood because the enzyme dihydrofolate reductase that converts folic acid to the biologically active forms is rate limiting. 

Evidence of a negative health effect of folic acid in blood is not consistent, and folic acid has no known cofactor function that would increase the likelihood of a causal role for free FA in disease development.
However, low vitamin B12 status in combination with high folic acid intake, in addition to the previously mentioned neuropathy risk, appeared to increase the risk of cognitive impairment in the elderly. 
Long-term use of folic acid dietary supplements in excess of 1,000 μg/day has been linked to an increase in prostate cancer risk.

When vitamin B9 is used orally at appropriate doses, folic acid is likely safe.

Oral use of vitamin B9 can cause:

-Bad taste in your mouth
-Nausea
-Loss of appetite
-Confusion
-Irritability
-Sleep pattern disturbance
People with allergies might have a reaction to vitamin B9 supplements. 
Warning signs of an allergic reaction include:

-Skin rash
-Itching
-Redness
-Difficulty breathing
-Excess folic acid is excreted in urine.

A high vitamin B9 intake can mask vitamin B-12 deficiency until its neurological effects become irreversible. 
This can typically be remedied by taking a supplement containing 100 percent of the daily value of both vitamin B9 and vitamin B-12.

FOOD LABELLING 

For U.S. food and dietary supplement labeling purposes the amount in a serving is expressed as a percent of Daily Value (%DV). 
For vitamin B9 labeling purposes 100% of the Daily Value was 400 μg. 
As of the 27 May 2016 update, it was kept unchanged at 400 μg. 
Compliance with the updated labeling regulations was required by 1 January 2020 for manufacturers with US$10 million or more in annual food sales, and by 1 January 2021 for manufacturers with lower volume food sales. 
A table of the old and new adult daily values is provided at Reference Daily Intake.

European Union regulations require that labels declare energy, protein, fat, saturated fat, carbohydrates, sugars, and salt. 
Voluntary nutrients may be shown if present in significant amounts. 
Instead of Daily Values, amounts are shown as percent of Reference Intakes (RIs). 
For vitamin B9, 100% RI was set at 200 μg in 2011.

DEFICIENCY

Vitamin B9 deficiency can be caused by unhealthy diets that do not include enough vegetables and other vitamin B9-rich foods; diseases in which folates are not well absorbed in the digestive system (such as Crohn's disease or celiac disease); some genetic disorders that affect levels of vitamin B9; and certain medicines (such as phenytoin, sulfasalazine, or trimethoprim-sulfamethoxazole). 
Vitamin B9 deficiency is accelerated by alcohol consumption, possibly by interference with folate transport.

Vitamin B9 deficiency may lead to glossitis, diarrhea, depression, confusion, anemia, and fetal neural tube and brain defects. 
Other symptoms include fatigue, gray hair, mouth sores, poor growth, and swollen tongue.
Vitamin B9 deficiency is diagnosed by analyzing a complete blood count (CBC) and plasma vitamin B12 and vitamin B9 levels. 

A serum folate of 3 μg/L or lower indicates deficiency. 
Serum folate level reflects vitamin B9 status, but erythrocyte vitamin B9 level better reflects tissue stores after intake. 
An erythrocyte vitamin B9 level of 140 μg/L or lower indicates inadequate vitamin B9 status. 
Serum vitamin B9 reacts more rapidly to folate intake than erythrocyte vitamin B9.

Since vitamin B9 deficiency limits cell division, erythropoiesis (production of red blood cells) is hindered. 
This leads to megaloblastic anemia, which is characterized by large, immature red blood cells. 

This pathology results from persistently thwarted attempts at normal DNA replication, DNA repair, and cell division, and produces abnormally large red cells called megaloblasts (and hypersegmented neutrophils) with abundant cytoplasm capable of RNA and protein synthesis, but with clumping and fragmentation of nuclear chromatin. Some of these large cells, although immature (reticulocytes), are released early from the marrow in an attempt to compensate for the anemia. 
Both adults and children need vitamin B9 to make normal red and white blood cells and prevent anemia, which causes fatigue, weakness, and inability to concentrate.

Increased homocysteine levels suggest tissue vitamin B9 deficiency, but homocysteine is also affected by vitamin B12 and vitamin B6, renal function, and genetics. 
One way to differentiate between vitamin B9 deficiency and vitamin B12 deficiency is by testing for methylmalonic acid (MMA) levels. 
Normal MMA levels indicate vitamin B9 deficiency and elevated MMA levels indicate vitamin B12 deficiency.

Vitamin B9 deficiency is treated with supplemental oral folic acid of 400 to 1000 μg per day. 
This treatment is very successful in replenishing tissues, even if deficiency was caused by malabsorption. 
People with megaloblastic anemia need to be tested for vitamin B12 deficiency before treatment with folic acid, because if the person has vitamin B12 deficiency, folic acid supplementation can remove the anemia, but can also worsen neurologic problems.
Cobalamin (vitamin B12) deficiency may lead to vitamin B9 deficiency, which, in turn, increases homocysteine levels and may result in the development of cardiovascular disease or birth defects.

History

In the 1920s, scientists believed vitamin B9 deficiency and anemia were the same condition. 
In 1931, researcher Lucy Wills made a key observation that led to the identification of vitamin B9 as the nutrient required to prevent anemia during pregnancy. 
Wills demonstrated that anemia could be reversed with brewer's yeast.
In the late 1930s, vitamin B9 was identified as the corrective substance in brewer's yeast. 

Vitamin B9 was first isolated via extraction from spinach leaves by Herschel K. Mitchell, Esmond E. Snell, and Roger J. Williams in 1941. 
The term "folic" is from the Latin word folium (which means leaf) because it was found in dark-green leafy vegetables.
Historic names included L.casei, factor vitamin Bc after research done in chicks and vitamin M after research done in monkeys.

Bob Stokstad isolated the pure crystalline form in 1943, and was able to determine its chemical structure while working at the Lederle Laboratories of the American Cyanamid Company.
This historical research project, of obtaining folic acid in a pure crystalline form in 1945, was done by the team called the "folic acid boys," under the supervision and guidance of Director of Research Dr. Yellapragada Subbarow, at the Lederle Lab, Pearl River, NY.
This research subsequently led to the synthesis of the antifolate aminopterin, which was used to treat childhood leukemia by Sidney Farber in 1948.

In the 1950s and 1960s, scientists began to discover the biochemical mechanisms of action for vitamin B9.
In 1960, researchers linked vitamin B9 deficiency to risk of neural tube defects.
In the late 1990s, the U.S. and Canadian governments decided that despite public education programs and the availability of folic acid supplements, there was still a challenge for women of child-bearing age to meet the daily vitamin B9 recommendations, which is when those two countries implemented vitamin B9 fortification programs. 
As of December 2018, 62 countries mandated food fortification with folic acid.

SOURCES OF VITAMIN B9 

Vitamin B9 can be found naturally in many foods. 
The primary animal sources of vitamin B9 includes liver, dairy products, egg yolk, and seafood. 
Natural primary plant sources are dark green leafy vegetables (e.g. spinach, romaine lettuce, asparagus, broccoli), beans, peanuts, sunflower seeds, fresh fruits, fruit juices, whole grains, wheat germ, and yeast. 
Additionally, in many countries, wheat and maize flours, rice, and processed foods utilizing these ingredients (e.g. breakfast cereals, biscuits, and pasta) are fortified or enriched with vitamin B9.

Vitamin B9 has variable bioavailability depending on the form and conditions of ingestion. 
In the form of folic acid from supplements, vitamin B9 is also 100% bioavailable when taken without food. 
When taken with food, folic acid is more bioavailable in the gut than its naturally occurring folate (85% vs 50% absorption respectively).

SYNONYMS

Folate
Folicet 
Folvite
FA 
N-(4-{[(2-amino-4-oxo-1,4-dihydropteridin-6-yl)methyl]amino}benzoyl)-L-glutamic acid 
pteroyl-L-glutamic acid
folacin 
vitamin B9
vitamin Bc
Pterylmonoglutamic acid 
PteGlu 
Vitamin M 
Pteroyl-L-glutamic acid