Key Concepts

  • Deficiency is rare in the U.S.
  • The RDA of vitamin B2 for adult males is 1.3 mg/day and 1.1 mg/day for adult females
  • Very little riboflavin is absorbed beyond 27 mg (20x RDA) per a single dose
  • No known toxicity at high doses
  • Food sources – dairy, eggs, mushrooms, meat, almonds, green leafy vegetables, grains (whole and enriched)
  • B Complex – $0.34/day



Have you ever taken a B-vitamin supplement and wondered why your pee was neon green? That due to vitamin B2, also known as riboflavin. There are a couple unique and important things to know about riboflavin. It is easily destroyed by light but fairly resistant to heat, oxidation, and acid.


Riboflavin is typically bound to a protein and must be freed to be absorbed. This process requires hydrochloric acid (HCl). HCl is the main component of gastric acid. Gastric acid is produced by the parietal cells in the stomach. Therefore, if there is a problem with HCl secretion, vitamin B2 absorption can be affected.

About ninety-five percent of riboflavin is absorbed in the proximal small intestine. Very little riboflavin is absorbed beyond 27 mg per a single dose.


Small amounts of riboflavin are stored in the liver, heart, and kidneys. The body maintains a pool of riboflavin stored in tissues that takes between 2-6 weeks to deplete if dietary intake is low or absent. This pool of riboflavin is generally available on demand as needed.

Typically ingested single dose amounts beyond 27 mg are excreted in the urine.

Recommended Dietary Allowances (RDAs)

The RDA of vitamin B2 for adult males is 1.3 mg/day and 1.1 mg/day for adult females.


More than 90% of dietary riboflavin is in the form of FAD (flavin adenine dinucleotide) or FMN (riboflavin-5’-phosphate). FMN and FAD are components of flavoproteins and key components in the metabolism of carbohydrates, fats, and proteins. They are important in oxidation-reduction reactions – the electron transport chain, CYP450 metabolism, and beta-oxidation. They are also involved in the metabolism of vitamin B6, niacin, and folate. Riboflavin is involved in dopamine synthesis, uric acid metabolism, and glutathione regeneration. The MTHFR enzyme is FAD-dependent.


Riboflavin deficiency is extremely rare in the United States. Riboflavin deficiency alters iron metabolism. Deficiencies can result in ariboflavinosis, cheilosis, angular stomatitis, glossitis, and seborrheic dermatitis.

Populations at increased risk for riboflavin deficiency: those with diabetes mellitus, under high stress, using oral contraceptives long-term, alcoholics.


No upper level intake (UL) is established for riboflavin and it does not appear to be toxic at high doses.

Food Sources

  • Beef liver, pan fried, 3 ounces – 2.9 mg, 171%
  • Mushrooms, portabella, sliced, grilled, ½ cup – 0.3 mg, 18%
  • Almonds, dry roasted, 1 ounce – 0.3 mg, 18%
  • Cheese, Swiss, 3 ounces – 0.3 mg, 18%
  • Egg, whole, scrambled, 1 large – 0.2 mg, 12%
  • Quinoa, cooked, 1 cup – 0.2 mg, 12%
  • Salmon, pink, canned, 3 ounces – 0.2 mg, 12%



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