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Red Cell Folate Testing

Unwarranted and Overutilized in the Era of Folic Acid Supplementation


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Folate

Slide 2

November 2010

Folate is a water-soluble B vitamin that is essential for adequate health. Folate, along with vitamin B12, is essential for DNA synthesis, repair, and methylation. Folate coenzymes are also integral in reactions involving one-carbon metabolism, and although there are various forms of methylated folate in the body, the primary form is 5-methyltetrahydrofolate. 5-methylTHF is also a cosubstrate required by methionine synthase for the conversion and demethylation of homocysteine to methionine *required to re-methylate homocysteine to form methionine, a reaction catalyzed by the enzyme methionine synthase. Homocysteine may also be re-methylated to methionine by other folate independent enzymes such as betaine homocysteine methyltransferase (BHMT) but generally to a much lower extent. Therefore, in the setting of folate deficiency there will be an accumulation of homocysteine. Folate and vitamin B12 (or cobalamin) metabolism are linked by the reaction that transfers a methyl group from 5-methyltetrahydrofolate to B12. Homocysteine, along with methylmalonic acid, will also be elevated in the setting of B12 deficiency, and a combination of MMA and homocysteine has been proposed by some to distinguish between B12 and folate deficiency.

* Bold section denotes correction made in August 2013.

Folate

 


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