Folate is concentrated in bile, and enterohepatic recirculation from the intestine accounts for considerable re-absorption and reuse of folate (about 100 mgday-1). Fecal folates mostly arise through biosynthesis of the vitamin by the gut microflora, with only a small contribution from unabsorbed dietary folate. Urinary excretion of intact folates accounts for only a small fraction of ingested folate under normal physiological conditions. The greater amount of excretion in urine is accounted for by products that arise from cleavage of the folate molecule at the C9-N10 bond, consisting of one or more pteridines and p-acetamido-benzoylglutamate. The rate of scission of the folate molecule increases during rapid-mitotic conditions such as pregnancy and rapid growth. Scission of folate is perhaps the major mechanism of folate turnover in the body.
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