Vitamin B2 (Riboflavin)

What Is Vitamin B2 (Riboflavin)?

Riboflavin is a water-soluble B vitamin that serves as the core component of two critical coenzymes: flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). Its name derives from its yellow color (riboflavin from ribose + Latin flavus, yellow), which gives urine a bright yellow hue at high intake — a harmless effect.

The RDA for adults is 1.3 mg/day for men and 1.1 mg/day for women. Pregnancy increases the requirement to 1.4 mg/day and lactation to 1.6 mg/day.

Key Functions

• Oxidation-reduction reactions: FMN and FAD act as electron carriers in the mitochondrial electron transport chain, facilitating ATP synthesis.
• Macronutrient metabolism: Required for the beta-oxidation of fatty acids, amino acid catabolism, and glucose oxidation.
• Antioxidant defense: Riboflavin is needed to regenerate glutathione, a major intracellular antioxidant, via glutathione reductase.
• Vitamin activation: Converts vitamin B6 and folate into their active coenzyme forms.

Deficiency and Food Sources

Isolated riboflavin deficiency (ariboflavinosis) is uncommon but presents with angular stomatitis (cracks at the corners of the mouth), glossitis (magenta-colored tongue), and seborrheic dermatitis. It typically occurs alongside other B vitamin deficiencies.

Best dietary sources include beef liver, dairy products (milk, yogurt, cheese), eggs, almonds, lean meats, and fortified grain products. Riboflavin is sensitive to ultraviolet light; milk stored in clear containers can lose up to 50% of its riboflavin content after several hours of light exposure.