Fundamentals of Human Nutrition/Folate< Fundamentals of Human Nutrition
Folate is a water-soluble B Vitamin. It is the term used for its natural occurring forms and is also known as pteroylglutamic acid . Folate’s natural form is a polyglutamate which is how the body receives it, this also known as its ‘bound’ form. Enzymes within the intestine hydrolyze it until it is a monoglutamate. The vitamin is then methylated and delivered to the liver and other cells within the body. The methylated form of folate is inactive and can only be activated by removing the methyl group using an enzyme and the vitamin B12.
The synthetic form of folate is referred to as folic acid, a monoglutamate, which is found in supplements and fortified foods. Folate is primarily used in the coenzyme THF (tetrahydrofolate) that transfers 1-carbon compounds in metabolism .
Folate cannot be synthesized by the body, so we must consume it to get an adequate intake. From the diet, folate is found in high quantities in legumes, fruits and vegetables. Of these, lentils and asparagus have an exceptional amount of folate .
Folate is critical for pregnant women because of its effects on growing infants and its ability to prevent major birth defects. Because of this the government has mandated that food be fortified with folic acid. The majority of these enriched foods are grains such as bread, pasta, rice and cereal .
Being the monoglutamate form, folic acid is a lot easier to absorb into the body then folate. This is why supplements are actually encouraged for folic acid, especially for pregnant women.
Folate is important in one-carbon metabolism
As a part of THF, folate accepts and donates 1-carbon groups for the synthesis of thymidine and purines as well as being involved in the regeneration of homocysteine to methionine, with the assistance of Vitamin B12 . It is thus important for cell maintenance, DNA and RNA synthesis, and maturation of red blood cells. This is what makes it so critical for pregnant women and infants.
Folate is absorbed about 50% from foods eaten and 100% from supplements . The RDA for folate is 400 μg/day DFE for ages 14 and up . Children need roughly 200 μg/day of DFE (dietary folate equivalent). However, since it is so critical for pregnant and nursing women, their RDA is 600 μg/day DFE. The upper limit of folate is 1000 μg/day for adults.
Folate is heavily involved with the Vitamin B12. Both are activated by the other and both are involved in the conversion of homocysteine to methionine. This is why the healthy function of folate cannot occur without adequate B12 supply.
Folate is seen as very important for women of child bearing age, especially those who are pregnant. If a pregnant woman does not meet her folate requirements, it is highly likely her child will be born with a neural tube defect, which is when the brain and spinal cord are not developed properly-- leading to disability or even death to the infant.
Folate deficiency also leads to a decrease in red blood cell and GI tract cell production. Because of this, the onset of a folate deficiency is characterized by anemia and GI tract deterioration. The anemia of a folate deficiency is called macrocytic or megaloblastic anemia. Folate’s presence is required for DNA to properly replicate red blood cells, so a lack of folate leads to a damaged DNA and immature red blood cells. The end result is very large red blood cells that cannot carry oxygen properly, travel through the bloodstream inefficiently and occasionally have nuclei.
Folate is implicated in many anticancer treatments, so it is very easy to develop a secondary folate deficiency. If a person is taking drugs with anticancer properties, many of them have similar structures to folate and they overtake folate and impede normal metabolism. Moreover, anticancer drugs affect both healthy and unhealthy cells, leading to a folate deficiency throughout the body .
Research hasn’t found much diseases from ingesting too much folate. However, there is an upper limit set because folate can mask a B12 deficiency. A B12 deficiency leads to nerve damage which in turn leads to irreversible damage to the brain and spinal cord. Furthermore, there are tentative claims that folate can lead to various forms of cancer .
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- Dietary Supplement Fact Sheet: Folate (2013). National Institutes of Health.