Which statement best describes enterohepatic circulation in folate handling?

• A. Folate is absorbed in the colon by passive diffusion.
• B. Folate is absorbed in the small intestine as monoglutamate with direct portal entry (no reduction).
• C. Folate is absorbed into portal circulation without enterohepatic involvement.
• D. Folate is excreted into bile and reabsorbed via enterohepatic circulation.

Answer: (D)

Entohepatic circulation refers to the recycling loop where substances excreted into bile return to the gut and can be reabsorbed. For folate, after absorption in the proximal small intestine (where folate is taken up as monoglutamate following brush-border deconjugation), some folate is delivered to the liver via the portal vein and a portion is secreted back into bile. This biliary excretion into the gut and subsequent reabsorption constitutes enterohepatic circulation, helping conserve folate stores. Therefore, the best description is that folate is excreted into bile and reabsorbed via enterohepatic circulation.

Colon absorption is not the main site for folate uptake; folate absorption occurs in the proximal small intestine. Folate is absorbed as monoglutamate after deconjugation, with portal entry occurring after absorption, but the existence of biliary recycling means enterohepatic involvement is indeed a feature of folate handling.