Riboflavin is essential for the metabolism of carbohydrates, amino acids, and lipids and supports antioxidant protection.
Rapidly growing, green leafy vegetables are rich in the vitamin; More than half of the vitamin is lost when flour is milled.
Riboflavin is stable when heated but can be readily destroyed by alkali and exposure to ultraviolet irradiation. Waxlined paper containers protect milk against riboflavin loss from exposure to sunlight.
Riboflavin deficiency becomes manifest after several months of deprivation of the vitamin. The initial symptoms include photophobia; tearing; burning and itching of the eyes; loss of visual acuity; and soreness and burning of lips, mouth, and tongue. More advanced symptoms include fissuring of the lips (cheilosis) and cracks in the skin at the corners of the mouth (angular stomatitis). It may manifest as a greasy eruption of the skin in the nasolabial folds, scrotum, or vulva; a purple, swollen tongue; capillary overgrowth around the cornea of the eye; and peripheral neuropathy.
Riboflavin is not known to be toxic; high oral doses are considered essentially nontoxic. However, high doses are not beneficial.
0.3-1.6 mg/day, depending on age and gender