Riboflavin

Riboflavin is a type of B vitamin that must be obtained from dietary sources because the human body cannot produce it. It is commonly known as vitamin B₂. Working with other B vitamins, it is important for cell growth and repair, normal reproduction, tissue health, and metabolism. Like iron, riboflavin is vital for producing red blood cells and indirectly plays a role in the transportation of oxygen throughout the body. It bolsters the immune system and helps maintain healthy skin and hair. Along with other B vitamins, riboflavin helps to maintain healthy vision, protects the nervous system, and is necessary for a healthy liver.

A water-soluble nutrient, riboflavin is disposed of through the urine and must, therefore, be replenished in the body every day. Natural sources of riboflavin include milk, meat, eggs, legumes, green vegetables, mushrooms, enriched flour, and almonds. While a vitamin B₂ deficiency is rare, it can lead to multiple significant complications. Treatment involves a diet with sufficient riboflavin-containing foods and vitamin supplements containing the recommended daily value for vitamin B₂.

Background

Riboflavin is pronounced "RIE bow flay vin" and was formerly known as vitamin G. Riboflavin is also called vitamin B₂ and is part of the vitamin B complex. In its chemical form, riboflavin is yellow-orange with poor solubility. It appears bright yellow in the urine when taken in excess and is colorless in its reduced form.

Riboflavin is often used in combination with other B vitamins in the vitamin B complex that includes vitamin B₁ (thiamine), B₂ (riboflavin), B₃ (niacin), B₅ (pantothenic acid), B₆ (pyridoxine), B₁₂ (cyanocobalamin), and folic acid. All B vitamins help the body convert carbohydrates into glucose to produce energy and aid in metabolizing fats and protein. All B complex vitamins are also water-soluble and are not stored by the body.

Riboflavin also works as an antioxidant, fighting harmful particles called free radicals. These free radicals can damage cells, contribute to the development of conditions such as heart disease and cancer, and speed up the aging process. By fighting free radicals, riboflavin can reduce or help prevent some of the damage they cause.

In particular, vitamin B₂ has been shown to be important for normal vision. Early studies indicated that riboflavin might help prevent damage to the lens of the eye, cataracts, and glaucoma, owing to its antioxidant effect. Taking riboflavin has also shown potential to reduce migraine headaches and to lower hyperhomocysteinemia (overly high amounts of homocysteine in the blood), though research is not conclusive. The common condition for which riboflavin has been proven effective is riboflavin deficiency, which can cause anemia, skin disorders, mouth sores, and other symptoms. In tandem with other B vitamins, riboflavin has also been investigated in treating the following: red cell aplasia; hyperhomocysteinemia; sickle cell anemia; canker sores; acne, dermatitis, eczema, and rosacea; eye fatigue; cataracts; glaucoma; memory loss; Alzheimer’s disease; anxiety; epilepsy; and multiple sclerosis. However, more research was required in these areas. In 2025, the US Food and Drug Administration (FDA) approved the use of Epioxa to treat the eye condition keratoconus in adults and children older than thirteen years.

Riboflavin is available in multivitamins and B-complex vitamins as well as supplements that contain only riboflavin, with amounts that vary by product. Since the recommended dose of riboflavin varies per person and medical condition, it is essential to consult with a healthcare professional to determine the proper dose.

Overview

Recommended daily intakes for riboflavin and other nutrients are developed by the Food and Nutrition Board at the Institute of Medicine. The board’s recommended dietary allowances (RDAs) for riboflavin are:

Males 14 years or older: 1.3 mg/day

Females 14 to 18 years: 1.0 mg/day

Females 19 years or older: 1.1 mg/day

Breastfeeding women: 1.6 mg/day

Pregnant women: 1.4 mg/day

Infants 0–6 months: 0.3 mg/day

Infants 7–12 months: 0.4 mg/day

Children 1–3 years: 0.5 mg/day

Children 4–8 years: 0.6 mg/day

Children 9–13 years: 0.9 mg/day

Since the processing of grains results in a significant loss of vitamin B₂, white flour, bread, and breakfast cereals are often enriched or fortified with riboflavin in the United States. Riboflavin is also added to pastas, baby foods, and meal replacement products and used as a food coloring agent. In whole brown rice, riboflavin is mostly retained, while free riboflavin is also naturally present in whole milk, egg whites, and egg yolks.

Most healthy people eating a well-balanced diet receive sufficient riboflavin. Some of the best dietary sources of riboflavin include milk, eggs, organ meats, soybeans, spinach, broccoli, mushrooms, wild rice, whole grains, wheat germ, almonds, and brewer’s yeast. Riboflavin is destroyed by exposure to light; hence, to protect riboflavin content, foods should be stored away from light and in opaque containers. Since the vitamin can also be depleted in water, steaming foods preserves more riboflavin than boiling, soaking, or frying.

Riboflavin does not usually cause side effects; when ingested in high doses, however, riboflavin may cause diarrhea, excess urine, and yellow-orange urine.

Since riboflavin is plentiful in the food supply of the Western world, a deficiency of riboflavin (vitamin B₂ deficiency) is uncommon. However, low riboflavin may result when dietary intake is insufficient (a primary deficiency) or when the body suffers from a condition that does not allow it to be absorbed or used (a secondary deficiency). Riboflavin deficiencies often occur in tandem with deficiencies in other water-soluble vitamins, as well as in older adults and individuals with chronic alcoholism, liver disease, eating disorders, diabetes, and inflammatory bowel disease. According to the Celiac Disease Foundation, people following a gluten-free diet (i.e., do not eat enriched wheat foods) could experience riboflavin deficiency. Lengthy phototherapy used to treat jaundice in newborns can cause degradation of riboflavin, risking its deficiency, and must be closely monitored.

Possible complications arising from a vitamin B₂ deficiency include: sore or inflamed throat; mouth or lip sores; cracks at the corners of the mouth; red, sore, or burning tongue; complications in metabolism; itchy, burning, or bloodshot eyes; light sensitivity; cataracts; itchy, dry, peeling skin; wrinkled arms and face; split fingernails and toenails; anemia; impaired nervous system function; weakness or fatigue.

Treatment for a vitamin B₂ deficiency involves consuming a diet with an adequate amount of riboflavin-containing foods and taking vitamin supplements with the recommended daily value for one’s age.

Bibliography

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