KIN 343 - 11.6 Vit B2 Overviews, DRIs and Sources

Overview of Riboflavin (Vitamin B2)

  • Definition: Riboflavin, or vitamin B2, is a water-soluble vitamin essential for energy metabolism.

  • Chemical Structure: Contains a ribose-like side chain; flavin refers to the yellow pigment, derived from the Latin term for yellow.

  • Initial Naming: Originally referred to as vitamin G but is now classified as a member of the B-vitamin group.

  • Interconversion: Riboflavin exists in multiple forms which can interconvert in the body.

Functions of Riboflavin

  • Forms of Riboflavin: Includes ribotol and flavin. Key phosphorylated forms include:

    • Flavin Mononucleotide (FMN): Formed by phosphorylation of riboflavin.

    • Flavin Adenine Dinucleotide (FAD): Consists of riboflavin, phosphate groups, and AMP; crucial for electron transport.

  • Role in Metabolism: FAD is instrumental in the transport of electrons from the TCA cycle to the electron transport chain, central to energy production in cells.

  • Reducing Equivalents: FADH2 provides reducing equivalents necessary for the biosynthesis of cellular components.

  • Importance in Cellular Processes: B vitamins, including riboflavin, are integral to metabolic pathways and facilitate energy production.

Dietary Reference Intakes (DRIs)

  • Recommended Daily Intake: Approximately 1 mg for adults from childhood to adulthood; increased demand during pregnancy and lactation due to requirements for infant development and breast milk content.

  • Upper Limit (UL): No established upper limit; excess riboflavin is efficiently excreted and causes urine to change color due to its pigment properties.

Food Sources of Riboflavin

  • Animal Sources: Generally rich sources; omnivores benefit from including meat and dairy in their diets.

  • Plant Sources: Good sources include whole grains and fortified cereals, while fruits have lower levels of riboflavin.

  • Vegetables and Legumes: Certain vegetables and legumes are excellent sources of riboflavin and other B vitamins, contributing to a well-rounded nutrient intake.

  • Processing Impact: Less processed foods tend to have higher concentrations of B vitamins, including riboflavin; e.g., spinach, though known for iron, also contains riboflavin and various micronutrients.