Where Is Folate Absorbed

Folates are absorbed primarily in the duodenum and jejunum within the acid microenvironment at the cell surface. Folic acid absorption is an active process that occurs primarily in the duodenum and jejunum. Following absorption, folic acid present in human and canine portal blood is not methylated, although methylation may occur later in the liver following reduction.

Both vitamin B 12 and folate are present in food as coenzymatically active forms bound to protein, from which they must be freed by processing or digestion prior to absorption. Folate is actively absorbed primarily from the upper third of the small intestine. 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 folate naturally present in food is absorbed.

Dietary folate is first converted to monoglutamate forms in the small intestine before absorption. Synthetic folic acid is directly absorbed. Once absorbed, both forms undergo reduction steps.

Folic acid and other folate forms are reduced by the enzyme Dihydrofolate Reductase (DHFR) into dihydrofolate (DHF) and then into tetrahydrofolate (THF). Learn about the two-step process of intestinal absorption of dietary folates. Discover the role of enzymes and transporters involved in this process.

The absorption of both vitamins is relatively limited to one section of the small intestine; the transporter for folate (PCFT) is restricted to the upper half of the small intestine, and the receptor for the intrinsic factor (IF)-cobalamin (cbl) complex is limited to the distal small intestine. (A) Folate is absorbed mainly in the upper small intestine, following which it is transported to the liver for distribution throughout the body. When consumed, food folates are hydrolyzed to the monoglutamate form in the gut prior to absorption by active transport across the intestinal mucosa [2].

Passive diffusion also occurs when pharmacological doses of folic acid are consumed. Folate (Folic Acid) Vitamin B9 Folate is the natural form of vitamin B9, water-soluble and naturally found in many foods. It 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 sources85% vs.

50%, respectively.