Riboflavin (Vitamin B2)
• Digestion & Absorption
• The form of riboflavin in food varies. In some foods riboflavin is found as free or protein-bound
riboflavin. In other foods, riboflavin is found as Flavin Mononucleotide (FMN) or Flavin
Adenine Dinucelotide (FAD).
• Need to remove protein and phosphate (phosphatases) to absorb. Riboflavin attached to protein
is freed by the action of hydrochloric acid and gastric and intestinal enzymes.
• Riboflavin in food as FMN and FAD must be freed prior to absorption. Within the intestinal
lumen, enzymes such as FAD pyrophosphatase and FMN phosphatase play an important role.
• Animal sources of riboflavin are thought to be better absorbed than plant sources.
• Better absorbed with meals (70% absorption) than fasting (15%).
• Divalent metals (Copper, Zinc, Iron, Manganese) may chelate riboflavin and inhibit absorption.
• Free riboflavin is absorbed by active transport (sodium-dependent), mainly in the duodenum.
• A small amount of riboflavin is absorbed in the large intestine