VITAMIN B2 (Riboflavin)

Vitamin B2 is a bright-yellow, B complex VITAMIN. This widely distributed vitamin functions in oxidation-reduction reactions. Riboflavin works together with the B vitamins THIAMIN, NIACIN and PANTOTHENIC ACID to oxidize FAT and CARBOHYDRATE to carbon dioxide to produce ENERGY. The complete oxidation of these fuels occurs via the KREB’S CYCLE, a sequence of enzyme-catalyzed steps that represents the major energy-yielding pathway of most tissues. Riboflavin is the parent Of FLAVIN ADENINE DINUCLEOTIDE (FAD) and flavin mononucleotide (FMN), two enzyme helpers (COENZYMES). Riboflavin participates in the body’s defense system to oxidize toxins and foreign compounds. It supports glutathione reductase; an enzyme that replenishes an important cellular ANTIOXIDANT called glutathione. This system represents a major defense against oxidative damage. In addition, the production of steroid HORMONES by the ADRENAL GLANDS requires riboflavin. More generally, riboflavin is essential for successful reproduction in experimental animals, for healthy skin, eyes, and nerve function. NOTE: THIS IS THE VITAMIN THAT CAUSES THE URINE TO BE SO YELLOW WHEN YOU TAKE A B-COMPLEX VITAMIN.

Possible Roles in Maintaining Health

Unlike niacin deficiency or thiamin deficiency, chronic riboflavin deficiency does not cause a distinctive human disease. ARIBOFLAVINOSIS a riboflavin deficiency disease, occurs in association with deficiencies of other B complex vitamins. Symptoms of riboflavin deficiency include FATIGUE, delayed wound healing, sore mouth, cracks in the corners of the mouth, tongue inflammation (GLOSSITIS), blurred vision and light sensitivity, and eczema of face and genitalia.


Riboflavin is widely distributed among foods, but the levels vary greatly. Rich sources include organ meats (LIVER, kidney and heart); dairy products (MILK, CHEESE, YOGURT); and BREWER”S YEAST. BREAKFAST CEREAL, enriched flour, almonds, lean meat, raw mushrooms, wheat bran, enriched cornmeal, soybean flour and dark-green leafy VEGETABLES are good sources. Fifty percent of the riboflavin in milk can be lost within two hours upon exposure to light. Storing milk in cartons rather than in glass bottles markedly reduces the loss. Riboflavin is destroyed by light and by heat. Up to 20% of riboflavin is lost from milk by evaporation or by PASTEURIZATION. Raw fruits and vegetables generally provide little riboflavin.

The U.S. enrichment program for white flour was initiated in 1941. Since then, riboflavin, as well as thiamin, niacin and iron, have been added to flour and cereal products that together account for an estimated 0.33 mg of riboflavin per day for a typical American. Riboflavin is non-toxic; excesses are excreted and turn urine yellow.


The RECOMMENDED DIETARY ALLOWANCE (RDA) of riboflavin is 1.7 mg per day for men and 1.3 mg per day for women between the ages of 25 and 50. The requirement increases somewhat for women who are pregnant or lactating. Anyone with a severely compromised diet is prone to B complex vitamin deficiency in general. This includes children of developing countries who consume inadequate eggs, meat, and milk or enriched foods; alcoholics; elderly persons with an imbalanced diet; people on severe weight loss programs; chronic users of fiber-based laxatives; those who use tranquilizers; and patients with HYPOTHYROIDISM. Vigorous EXERCISE can increase the requirement of riboflavin in women.

Haller, J., “Vitamins for the Elderly: Reducing Disability and

Improving the Quality of Life,”” Aging, Clinical and Experimental

Research, 5: supp. 1 (1993), pp. 65-70.