Dietary riboflavin must be liberated as free riboflavin prior to absorption; therefore, covalently bound forms are unavailable for absorption. Most dietary riboflavin is in the form of noncovalently bound coenzymes, primarily flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), and free riboflavin is liberated following the action of the digestive enzymes. Riboflavin is absorbed in the upper ileum by an active, saturable carrier; although passive diffusion may also occur at high concentrations. The number of carriers appears to be regulated in direct proportion to the need for riboflavin. Following absorption, riboflavin is phosphorylated in the mucosal cell, which aids active transport through a trapping mechanism, followed by release of free riboflavin into the bloodstream.148,149

Riboflavin is also synthesized by the microflora of the large intestine, and small amounts are absorbed by an active carrier present in the colonic cells. Excess riboflavin is excreted by the kidney, primarily unchanged, although small amounts may appear as metabolites. Fecal levels are usually high because of synthesis by the microflora of the colon and are not an indicator of increased excretion or decreased absorption.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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